Back Clinic Imaging & Diagnostics Team. Dr. Alex Jimenez works with top-rated diagnosticians and imaging specialists. In our association, imaging specialists provide fast, courteous, and top-quality results. In collaboration with our offices, we provide the quality of service our patients’ mandate and deserve. Diagnostic Outpatient Imaging (DOI) is a state-of-the-art Radiology center in El Paso, TX. It is the only center of its kind in El Paso, owned and operated by a Radiologist.
This means when you come to DOI for a radiologic exam, every detail, from the design of the rooms, the choice of the equipment, the hand-picked technologists, and the software which runs the office, is carefully chosen or designed by the Radiologist and not by an accountant. Our market niche is one center of excellence. Our values related to patient care are: We believe in treating patients the way we would treat our family and we will do our best to ensure that you have a good experience at our clinic.
10% of all fractures. 2nd m/c following femoral neck Fx. Demographics: active young males and older osteoporotic females
Stable Fx: overall prognosis is good
Unstable Fx: require ORIF. 15%-20% chances of 2nd OA.
Role of imaging is to determine the complexity, stability and care planning (i.e., operative vs. conservative)
Weber classification considers tearing of distal tibial-fibular syndesmosis and potential instability
Weber A – below syndesmosis. Stable, typically avulsion of the distal fibular malleolus
Weber B – at the level of syndesmosis: may be outside syndesmosis and stable or tearing syndesmosis and unstable
Weber C – above syndesmosis. Always unstable d/t tearing of syndesmosis
Variations of fractures may involve the position/role of the talus bone during Fx (e.g., abduction, adduction, rotation, etc.) this is known as Lauge-Hanson classification
Reveal infrasyndesmotic Fx of fibular malleolus (Weber A)
Stable Injury
Conservative care in the form of short-leg walking cast/boot can be used. Good recovery. If no evidence of osteochondral injury, relatively low chances of post-traumatic OA
No further imaging required. MRI may help to reveal bone contusion and osteochondral injury
Weber B at Level of Syndesmosis
Can be stable or unstable. On occasions, the decision is made during operative exploration.
CT scanning may help with further evaluation
Management: depends on stability. Additional stabilization required if syndesmosis is ruptured
Weber C
AP, medial oblique and lateral views reveal Weber C – suprasyndesmotic injury with abnormal joint widening d/t disruption of the tib-fib syndesmosis. Very unstable injury.
Occasionally, when Weber C Fx positioned 6-cm from the tip of the lateral malleolus, it may be termed as Pott’s ankle Fx (name after Percival Pott’s who has proposed the original classification of ankle fractures based on their stability and degree of rotation). The term is somewhat outdated.
Management: operative with additional stabilization of the syndesmosis
Maisonneuve Fracture
Often spiral fracture of the proximal fibula combined with an unstable ankle injury
No immediate ankle fracture is noted radiographically, thus can be missed on ankle views and require tibia and fibula views
Rad features: widening of the ankle d/t syndesmosis tear and sometimes deltoid ligament disruption. Interosseous membrane is torn with proximal fibular Fx caused by pronation with external-rotation force
Management: operative
Bimalleolar & Trimalleolar Fx
Above top images Bimalleolar Fx v. unstable, the result of pronation and abduction/external rotation. Rx: ORIF.
Trimalleolar Fx: 3-parts ankle Fx. Medial and lateral malleolus and avulsion of the posterior aspect of tibial plafond. More unstable. Rx: operative
Tillaux Fx
Pediatric Fx affecting older child when the medial side of the physis is closed or about to close with lateral side till open. Avulsion by the anterior tibi-fibular ligament. Complications: 2nd dry/premature OA. Rx: can be conservative if stable by boot cast immobilization.
Pediatric Growth Plate Injuries
Salter-Harris classification helps to diagnose and prognosticate physeal injuries.
Helpful mnemonic: SALTR
S: type 1-slip through the growth plate
A: type 2-above, Fx extends into the metaphysis
L: type 3-lower, intra-articular Fx extends through the epiphysis
T: type4, “through” Fx extends through all: physis, metaphysis, and epiphysis.
R: type 5, “ruined.” Crush injury to physis leading to complete death of the growth plate
Type 1 and 5: present with no fracture
Type 2: has the best prognosis and considered the most common.
Management: referral to a pediatric orthopedic surgeon
Complications: early physis closure, limb shortening, premature OA and others.
Calcaneal Fracture
Most frequent tarsal Fx. 17% open Fx
Mechanisms: axial loading (intra-articular Fx into sub-talar and calcaneal-cuboid joints in 75% cases). Avulsion by Achilles tendon (m/c in osteoporotic bone). Stress (fatigue) Fx.
Intra-articular Fx carries a poor prognosis. Typically comminuted. Rx: operative.
B/I calcaneal intra-articular fx with associated vertebra compression Fx with associated vertebral compression Fx (T10-L2) often termed Casanova aka Don Juan (Lover’s) fx.
Imaging: x-radiography with added “heel view” 1st step. CT scanning is best for Dx and pre-op planning.
M/C fractured tarsal bone is the Talus. M/C region: talar neck (30-50%). Mechanism: Axial loading in dorsiflexion. Complications: Ischemic osteonecrosis (AVN) of the talus. Premature (2nd OA). Imaging: 1st step: radiographs, CT can be helpful with further delineation
Hawkins classification helps with Dx, prognosis & treatment. “Hawkins sign’ on plain film/CT scan may help with AVN Dx. (above blue arrows indicate good prognosis d/t radiolucent line indicating no AVN because the bone is vascularized and hence resorbed)
Rx: Type 1: conservative with short leg cast or boot (risk of AVN-0-15%), Type 2-4-ORIF (risk of AVN 50%-100%)
Sagittal Fluid Sensitive MR slice showing large synovial popliteal (Baker’s) cyst (above top image) and sizeable synovial effusion (above bottom image)
Note multiple patchy dark signal areas on both images, representing fibrinoid inflammatory deposits aka “rice bodies” a characteristic MRI feature of RA
Management Rheumatological Referral & DRM
Conservative management followed by operative care in complicated cases of tendon ruptures and joints dislocations
Supplemental reading:
Diagnosis and Management of Rheumatoid Arthritis – AAFP
Septic arthritis – d/t bacterial or fungal contamination of the joint. SA may cause rapid joint destruction and requires prompt Dx and antibiotic administration
Joints affected: large joints with rich blood supply (knee 50%>hips>shoulders).
Routs of Infection:
1) Hematogenous is m/c
2) Spread from an adjacent site
3) Direct implantation (e.g., trauma, iatrogenically)
Patients at risk: children, diabetics, immunocompromised, pre-existing joint damage/inflammation, e.g., RA, etc.
I.V. drug users are particularly at risk and also may contaminate atypical joints “the S joints” SIJ, SCJ, Symphysis pubis, ACJ, etc.
Clinically: may vary and depends on host immune response and bacterial virulence. May present with rapid onset or exacerbation of pre-existing joint pain, swelling, limitation of ROM. General signs of malaise, fever, fatigue and elevated ESR, CRP, Leucocytosis may be present.
N.B. Diabetics and immunocompromised may present with fewer manifestations and lack of fever d/t declining immune response
Dx: clinical, radiological and laboratory. Arthrocentesis may be necessary for culture, cell count and purulent synovial examination
Management: I.V. antibiotics
Imaging Dx: begins with radiography but in the early stage most likely will be unremarkable. MRI can be sensitive and help with early identification of joint effusion, bone edema, etc. US may be helpful in the superficial joints and children. US helps with needle guidance. Bone scintigraphy may be used occaisonally if MRI is contraindicated
Routes of Joint Contamination
1. Hematogenous (M/C)
2. Spread from the adjacent site
3. Direct inoculation
M/C organism-Staph aureus
N.B Gonococcal infection may be a top differential in some cases
IV drug users: Pseudomonas, candida
Sickle cell: Salmonella
Animal (cats/dogs) bites: Pasteurella
Occasionally fungal contamination may occur
Radiography
Initially non-specific ST/joint effusion, obscuration/distortion of fat planes. Because it takes 30% of compact and 50-75% trabecular bone to be destroyed before seen on x-rays, radiography is insensitive to some of the early changes. MR imaging is the preferred modality
If MRI is not available or contraindicated. Bone scintigraphy with Tc-99 MDT can help
In children, US preferred to avoid ionizing radiation. In children, US can be more sensitive than in adults due to lack of bone maturation
Radiographic Dx
Early findings are unrewarding. Early features may include joint widening d/t effusion. Soft tissue swelling and obscuration/displacement of fat planes
1-2 weeks: periarticular and adjacent osseous changes are manifesting as patchy demineralization, moth-eaten, permeating bone destruction, loss, and indistinctness of the epiphyseal “white cortical line” with an increase in soft tissue swelling. MRI may be helpful with early Dx.
Late features: complete joint destruction and ankyloses
N.B. Septic arthritis may progress rapidly within days and requires early I.V. antibiotic to prevent major joint destruction
T1 & T2 Knee MRI
T1 (above left) and T2 fat-sat sagittal knee MRI slices reveal loss of normal marrow signal on T1 and increase on T2 due to septic edema. Bone sequestrum d/t osteomyelitis progressing into septic arthritis is noted. Marked joint effusion with adjacent soft tissue edema is seen. Dx: OSM and septic arthritis
Imaging may help the Dx of the septic joint. However, the final Dx is based on Hx, physical examination, blood tests and most importantly synovial aspiration (arthrocentesis)
Synovial fluid should be sent for Gram staining, culture, glucose testing, leukocyte count, and differential determination
ESR/CRP may be elevated
Synovial fluid: WBC can be 50,000-60,000/ul, with 80% neutrophils with depleted glucose levels Gram stain: in 75% gram-positive cocci. Gram staining is less sensitive in gonococcal infection with only 25% of cultures +
In 9% of cases, blood cultures are the only source of pathogen identification and should be obtained before antibiotic treatment
Gout: MSU deposition in and around joints and soft tissues. Elevated levels of serum uric acid (UA) (>7mg/dL) caused by overproduction or under-excretion of uric acid
Once UA reached/exceeded 7mg/dL, it will deposit in the peripheral tissues. Primary gout: disturbed metabolism of nucleic acids and purines break down. Secondary gout: increased cell turnover: Psoriasis, leukemia, multiple myeloma, hemolysis, chemotherapy, etc.
Gout presents with 5-characteristic stages:
1)asymptomatic hyperuricemia (years/decades)
acute attacks of gouty arthritis (waxes and wanes and lasts for several years)
Interval phase between attacks
Chronic tophaceous gout
Gouty nephropathy
Clinical Presentation
Depends� on stages
Acute attacks: acute joint pain “first and the worst” even painful to light touch
DDx: septic joint (both may co-exist) bursitis etc.
Gouty arthritis typically presents as monoarthropathy
Chronic tophaceous stage: deposits in joints, ear pinna, ocular structures, and other regions. Nephrolithiasis etc. Men>women. Obesity, diet, and age >50-60.
Radiography: early attacks are unremarkable and may present as non-specific joint effusion
Chronic tophaceous gout radiography: punched out peri-articular, para-articular and intraosseous erosions with overhanging edges. A characteristic rim of sclerosis and internal calcification, soft tissue tophi. Target sites: lower extremity m/c
Rx: allopurinol, colchicine (esp. preventing acute episodes and maintenance)
Synovial Aspiration
Synovial aspiration with polarized microscopy reveal negatively birefringent needle-shaped MSU crystals with large inflammatory PMN presence. DDx: positively birefringent rhomboid-shaped CPPD crystals (above bottom right) seen in Pseudogout and CPPD
Large S.T.
Density and joint effusion punched out osseous erosion with overhanging margins, overall preservation of bone density, internal calcifications Dx: chronic tophaceous gout
MRI Gout Features
Erosions with overhanging margins, a low signal on T1 and high on T2 and fat-suppressed images. Peripheral contrast enhancement of tophaceous deposits d/t granulation tissue
Dx: final Dx; synovial aspiration and polarized microscopy
The knee is the largest joint in the human body, where the complex structures of the lower and upper legs come together. Consisting of three bones, the femur, the tibia, and the patella which are surrounded by a variety of soft tissues, including cartilage, tendons and ligaments, the knee functions as a hinge, allowing you to walk, jump, squat or sit. As a result, however, the knee is considered to be one of the joints that are most prone to suffer injury. A knee injury is the prevalent cause of knee pain.
A knee injury can occur as a result of a direct impact from a slip-and-fall accident or automobile accident, overuse injury from sports injuries, or even due to underlying conditions, such as arthritis. Knee pain is a common symptom which affects people of all ages. It may also start suddenly or develop gradually over time, beginning as a mild or moderate discomfort then slowly worsening as time progresses. Moreover, being overweight can increase the risk of knee problems. The purpose of the following article is to discuss the evaluation of patients presenting with knee pain and demonstrate their differential diagnosis.
Abstract
Knee pain is a common presenting complaint with many possible causes. An awareness of certain patterns can help the family physician identify the underlying cause more efficiently. Teenage girls and young women are more likely to have patellar tracking problems such as patellar subluxation and patellofemoral pain syndrome, whereas teenage boys and young men are more likely to have knee extensor mechanism problems such as tibial apophysitis (Osgood-Schlatter lesion) and patellar tendonitis. Referred pain resulting from hip joint pathology, such as slipped capital femoral epiphysis, also may cause knee pain. Active patients are more likely to have acute ligamentous sprains and overuse injuries such as pes anserine bursitis and medial plica syndrome. Trauma may result in acute ligamentous rupture or fracture, leading to acute knee joint swelling and hemarthrosis. Septic arthritis may develop in patients of any age, but crystal-induced inflammatory arthropathy is more likely in adults. Osteoarthritis of the knee joint is common in older adults. (Am Fam Physician 2003;68:917-22. Copyright� 2003 American Academy of Family Physicians.)
Introduction
Determining the underlying cause of knee pain can be difficult, in part because of the extensive differential diagnosis. As discussed in part I of this two-part article,1 the family physician should be familiar with knee anatomy and common mechanisms of injury, and a detailed history and focused physical examination can narrow possible causes. The patient�s age and the anatomic site of the pain are two factors that can be important in achieving an accurate diagnosis (Tables 1 and 2). �
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Children and Adolescents
Children and adolescents who present with knee pain are likely to have one of three common conditions: patellar subluxation, tibial apophysitis, or patellar tendonitis. Additional diagnoses to consider in children include slipped capital femoral epiphysis and septic arthritis.
Patellar Subluxation
Patellar subluxation is the most likely diagnosis in a teenage girl who presents with giving-way episodes of the knee.2 This injury occurs more often in girls and young women because of an increased quadriceps angle (Q angle), usually greater than 15 degrees.
Patellar apprehension is elicited by subluxing the patella laterally, and a mild effusion is usually present. Moderate to severe knee swelling may indicate hemarthrosis, which suggests patellar dislocation with osteochondral fracture and bleeding.
Tibial Apophysitis
A teenage boy who presents with anterior knee pain localized to the tibial tuberosity is likely to have tibial apophysitis or Osgood- Schlatter lesion3,4 (Figure 1).5 The typical patient is a 13- or 14-year-old boy (or a 10- or 11-year-old girl) who has recently gone through a growth spurt.
The patient with tibial apophysitis generally reports waxing and waning of knee pain for a period of months. The pain worsens with�squatting, walking up or down stairs, or forceful contractions of the quadriceps muscle. This overuse apophysitis is exacerbated by jumping and hurdling because repetitive hard landings place excessive stress on the insertion of the patellar tendon.
On physical examination, the tibial tuberosity is tender and swollen and may feel warm. The knee pain is reproduced with the resisted active extension or passive hyperflexion of the knee. No effusion is present. Radiographs are usually negative; rarely, they show avulsion of the apophysis at the tibial tuberosity. However, the physician must not mistake the normal appearance of the tibial apophysis for an avulsion fracture. �
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Patellar Tendonitis
Jumper�s knee (irritation and inflammation of the patellar tendon) most commonly occurs in teenage boys, particularly during a growth spurt2 (Figure 1).5 The patient reports vague anterior knee pain that has persisted for months and worsens after activities such as walking down stairs or running.
On physical examination, the patellar tendon is tender, and the pain is reproduced by resisted knee extension. There is usually no effusion. Radiographs are not indicated.
Slipped Capital Femoral Epiphysis
A number of pathologic conditions result in referral of pain to the knee. For example, the possibility of slipped capital femoral epiphysis must be considered in children and teenagers who present with knee pain.6 The patient with this condition usually reports poorly localized knee pain and no history of knee trauma.
The typical patient with slipped capital femoral epiphysis is overweight and sits on the examination table with the affected hip slightly flexed and externally rotated. The knee examination is normal, but hip pain is elicited with passive internal rotation or extension of the affected hip.
Radiographs typically show displacement of the epiphysis of the femoral head. However, negative radiographs do not rule out the diagnosis in patients with typical clinical findings. Computed tomographic (CT) scanning is indicated in these patients.
Osteochondritis Dissecans
Osteochondritis dissecans is an intra-articular osteochondrosis of unknown etiology that is characterized by degeneration and recalcification of articular cartilage and underlying bone. In the knee, the medial femoral condyle is most commonly affected.7
The patient reports vague, poorly localized knee pain, as well as morning stiffness or recurrent effusion. If a loose body is present, mechanical symptoms of locking or catching of the knee joint also may be reported. On physical examination, the patient may demonstrate quadriceps atrophy or tenderness along the involved chondral surface. A mild joint effusion may be present.7
Plain-film radiographs may demonstrate the osteochondral lesion or a loose body in the knee joint. If osteochondritis dissecans is suspected, recommended radiographs include anteroposterior, posteroanterior tunnel, lateral, and Merchant�s views. Osteochondral lesions at the lateral aspect of the medial femoral condyle may be visible only on the posteroanterior tunnel view. Magnetic resonance imaging (MRI) is highly sensitive in detecting these abnormalities and is indicated in patients with a suspected osteochondral lesion.7 �
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A knee injury caused by sports injuries, automobile accidents, or an underlying condition, among other causes, can affect the cartilage, tendons and ligaments which form the knee joint itself. The location of the knee pain can differ according to the structure involved, also, the symptoms can vary. The entire knee may become painful and swollen as a result of inflammation or infection, whereas a torn meniscus or fracture may cause symptoms in the affected region. Dr. Alex Jimenez D.C., C.C.S.T. Insight
Adults
Overuse Syndromes
Anterior Knee Pain. Patients with patellofemoral pain syndrome (chondromalacia patellae) typically present with a vague history of mild to moderate anterior knee pain that usually occurs after prolonged periods of sitting (the so-called �theater sign�).8 Patellofemoral pain syndrome is a common cause of anterior knee pain in women.
On physical examination, a slight effusion may be present, along with patellar crepitus on the range of motion. The patient�s pain may be reproduced by applying direct pressure to the anterior aspect of the patella. Patellar tenderness may be elicited by subluxing the patella medially or laterally and palpating the superior and inferior facets of the patella. Radiographs usually are not indicated.
Medial Knee Pain. One frequently overlooked diagnosis is medial plica syndrome. The plica, a redundancy of the joint synovium medially, can become inflamed with repetitive overuse.4,9 The patient presents with acute onset of medial knee pain after a marked increase in usual activities. On physical examination, a tender, mobile nodularity is present at the medial aspect of the knee, just anterior to the joint line. There is no joint effusion, and the remainder of the knee examination is normal. Radiographs are not indicated.
Pes anserine bursitis is another possible cause of medial knee pain. The tendinous insertion of the sartorius, gracilis, and semitendinosus muscles at the anteromedial aspect of the proximal tibia forms the pes anserine bursa.9 The bursa can become inflamed as a result of overuse or a direct contusion. Pes�anserine bursitis can be confused easily with a medial collateral ligament sprain or, less commonly, osteoarthritis of the medial compartment of the knee. �
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The patient with pes anserine bursitis reports pain at the medial aspect of the knee. This pain may be worsened by repetitive flexion and extension. On physical examination, tenderness is present at the medial aspect of the knee, just posterior and distal to the medial joint line. No knee joint effusion is present, but there may be slight swelling at the insertion of the medial hamstring muscles. Valgus stress testing in the supine position or resisted knee flexion in the prone position may reproduce the pain. Radiographs are usually not indicated.
Lateral Knee Pain. Excessive friction between the iliotibial band and the lateral femoral condyle can lead to iliotibial band tendonitis.9 This overuse syndrome commonly occurs in runners and cyclists, although it may develop in any person subsequent to activity involving repetitive knee flexion. The tightness of the iliotibial band, excessive foot pronation, genu varum, and tibial torsion are predisposing factors.
The patient with iliotibial band tendonitis reports pain at the lateral aspect of the knee joint. The pain is aggravated by activity, particularly running downhill and climbing stairs. On physical examination, tenderness is present at the lateral epicondyle of the femur, approximately 3 cm proximal to the joint line. Soft tissue swelling and crepitus also may be present, but there is no joint effusion. Radiographs are not indicated.
Noble�s test is used to reproduce the pain in iliotibial band tendonitis. With the patient in a supine position, the physician places a thumb over the lateral femoral epicondyle as the�patient repeatedly flexes and extends the knee. Pain symptoms are usually most prominent with the knee at 30 degrees of flexion.
Popliteus tendonitis is another possible cause of lateral knee pain. However, this condition is fairly rare.10
Trauma
Anterior Cruciate Ligament Sprain. Injury to the anterior cruciate ligament usually occurs because of noncontact deceleration forces, as when a runner plants one foot and sharply turns in the opposite direction. Resultant valgus stress on the knee leads to anterior displacement of the tibia and sprain or rupture of the ligament.11 The patient usually reports hearing or feeling a �pop� at the time of the injury and must cease activity or competition immediately. Swelling of the knee within two hours after the injury indicates rupture of the ligament and consequent hemarthrosis.
On physical examination, the patient has a moderate to severe joint effusion that limits the range of motion. The anterior drawer test may be positive, but can be negative because of hemarthrosis and guarding by the hamstring muscles. The Lachman test should be positive and is more reliable than the anterior drawer test (see text and Figure 3 in part I of the article1).
Radiographs are indicated to detect possible tibial spine avulsion fracture. MRI of the knee is indicated as part of a presurgical evaluation.
Medial Collateral Ligament Sprain. Injury to the medial collateral ligament is fairly common and is usually the result of acute trauma. The patient reports a misstep or collision that places valgus stress on the knee, followed by the immediate onset of pain and swelling at the medial aspect of the knee.11
On physical examination, the patient with medial collateral ligament injury has point tenderness at the medial joint line. Valgus stress testing of the knee flexed to 30 degrees reproduces the pain (see text and Figure 4 in part I of this article1). A clearly defined endpoint on valgus stress testing indicates a grade 1�or grade 2 sprain, whereas complete medial instability indicates full rupture of the ligament (grade 3 sprain).
Lateral Collateral Ligament Sprain. Injury of the lateral collateral ligament is much less common than the injury of the medial collateral ligament. Lateral collateral ligament sprain usually results from varus stress to the knee, as occurs when a runner plants one foot and then turns toward the ipsilateral knee.2 The patient reports acute onset of lateral knee pain that requires prompt cessation of activity.
On physical examination, point tenderness is present at the lateral joint line. Instability or pain occurs with varus stress testing of the knee flexed to 30 degrees (see text and Figure 4 in part I of this article1). Radiographs are not usually indicated.
Meniscal Tear. The meniscus can be torn acutely with a sudden twisting injury of the knee, such as may occur when a runner suddenly changes direction.11,12 Meniscal tear also may occur in association with a prolonged degenerative process, particularly in a patient with an anterior cruciate ligament-deficient knee. The patient usually reports recurrent knee pain and episodes of catching or locking of the knee joint, especially with squatting or twisting of the knee.
On physical examination, a mild effusion is usually present, and there is tenderness at the medial or lateral joint line. Atrophy of the vastus medialis obliquus portion of the quadriceps muscle also may be noticeable. The McMurray test may be positive (see Figure 5 in part I of this article1), but a negative test does not eliminate the possibility of a meniscal tear.
Plain-film radiographs usually are negative and seldom are indicated. MRI is the radiologic test of choice because it demonstrates most significant meniscal tears.
Infection
Infection of the knee joint may occur in patients of any age but is more common in those whose immune system has been weakened by cancer, diabetes mellitus, alcoholism,�acquired immunodeficiency syndrome, or corticosteroid therapy. The patient with septic arthritis reports abrupt onset of pain and swelling of the knee with no antecedent trauma.13
On physical examination, the knee is warm, swollen, and exquisitely tender. Even slight motion of the knee joint causes intense pain.
Arthrocentesis reveals turbid synovial fluid. Analysis of the fluid yields a white blood cell count (WBC) higher than 50,000 per mm3 (50 ? 109 per L), with more than 75 percent (0.75) polymorphonuclear cells, an elevated protein content (greater than 3 g per dL [30 g per L]), and a low glucose concentration (more than 50 percent lower than the serum glucose concentration).14 Gram stain of the fluid may demonstrate the causative organism. Common pathogens include Staphylococcus aureus, Streptococcus species, Haemophilus influenza, and Neisseria gonorrhoeae.
Hematologic studies show an elevated WBC, an increased number of immature polymorphonuclear cells (i.e., a left shift), and an elevated erythrocyte sedimentation rate (usually greater than 50 mm per hour).
Older Adults
Osteoarthritis
Osteoarthritis of the knee joint is a common problem after 60 years of age. The patient presents with knee pain that is aggravated by weight-bearing activities and relieved by rest.15 The patient has no systemic symptoms but usually awakens with morning stiffness that dissipates somewhat with activity. In addition to chronic joint stiffness and pain, the patient may report episodes of acute synovitis.
Findings on physical examination include decreased range of motion, crepitus, a mild joint effusion, and palpable osteophytic changes at the knee joint.
When osteoarthritis is suspected, recommended radiographs include weight-bearing anteroposterior and posteroanterior tunnel views, as well as non-weight-bearing Merchants and lateral views. Radiographs show�joint-space narrowing, subchondral bony sclerosis, cystic changes, and hypertrophic osteophyte formation.
Crystal-Induced Inflammatory Arthropathy
Acute inflammation, pain, and swelling in the absence of trauma suggest the possibility of a crystal-induced inflammatory arthropathy such as gout or pseudogout.16,17 Gout commonly affects the knee. In this arthropathy, sodium urate crystals precipitate in the knee joint and cause an intense inflammatory response. In pseudogout, calcium pyrophosphate crystals are the causative agents.
On physical examination, the knee joint is erythematous, warm, tender, and swollen. Even minimal range of motion is exquisitely painful.
Arthrocentesis reveals clear or slightly cloudy synovial fluid. Analysis of the fluid yields a WBC count of 2,000 to 75,000 per mm3 (2 to 75 ? 109 per L), a high protein content (greater than 32 g per dL [320 g per L]), and a glucose concentration that is approximately 75 percent of the serum glucose con- centration.14 Polarized-light microscopy of the synovial fluid displays negatively birefringent rods in the patient with gout and positively birefringent rhomboids in the patient with pseudogout.
Popliteal Cyst
The popliteal cyst (Baker�s cyst) is the most common synovial cyst of the knee. It originates from the posteromedial aspect of the knee joint at the level of the gastrocnemio-semimembranous bursa. The patient reports insidious onset of mild to moderate pain in the popliteal area of the knee.
On physical examination, palpable fullness is present at the medial aspect of the popliteal area, at or near the origin of the medial head of the gastrocnemius muscle. The McMurray test may be positive if the medial meniscus is injured. Definitive diagnosis of a popliteal cyst may be made with arthrography, ultrasonography, CT scanning, or, less commonly, MRI.
The authors indicate that they do not have any conflicts of interest. Sources of funding: none reported.
In conclusion, although the knee is the largest joint in the human body where the structures of the lower extremities meet, including the femur, the tibia, the patella, and many other soft tissues, the knee can easily suffer damage or injury and result in knee pain. Knee pain is one of the most common complaints among the general population, however, it commonly occurs in athletes. Sports injuries, slip-and-fall accidents, and automobile accidents, among other causes, can lead to knee pain.
As described in the article above, diagnosis is essential towards determining the best treatment approach for each type of knee injury, according to their underlying cause. While the location and the severity of the knee injury may vary depending on the cause of the health issue, knee pain is the most common symptom. Treatment options, such as chiropractic care and physical therapy, can help treat knee pain. The scope of our information is limited to chiropractic and spinal health issues. To discuss the subject matter, please feel free to ask Dr. Jimenez or contact us at�915-850-0900�.
Curated by Dr. Alex Jimenez �
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Additional Topic Discussion: Relieving Knee Pain without Surgery
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Knee pain is a well-known symptom which can occur due to a variety of knee injuries and/or conditions, including�sports injuries. The knee is one of the most complex joints in the human body as it is made-up of the intersection of four bones, four ligaments, various tendons, two menisci, and cartilage. According to the American Academy of Family Physicians, the most common causes of knee pain include patellar subluxation, patellar tendinitis or jumper’s knee, and Osgood-Schlatter disease. Although knee pain is most likely to occur in people over 60 years old, knee pain can also occur in children and adolescents. Knee pain can be treated at home following the RICE methods, however, severe knee injuries may require immediate medical attention, including chiropractic care.
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4. Stanitski CL. Anterior knee pain syndromes in the adolescent. Instr Course Lect 1994;43:211-20.
5. Tandeter HB, Shvartzman P, Stevens MA. Acute knee injuries: use of decision rules for selective radiograph ordering. Am Fam Physician 1999;60: 2599-608.
6. Waters PM, Millis MB. Hip and pelvic injuries in the young athlete. In: DeLee J, Drez D, Stanitski CL, eds. Orthopaedic sports medicine: principles and practice. Vol. III. Pediatric and adolescent sports medicine. Philadelphia: Saunders, 1994:279-93.
7. Schenck RC Jr, Goodnight JM. Osteochondritis dis- secans. J Bone Joint Surg [Am] 1996;78:439-56.
8. Ruffin MT 5th, Kiningham RB. Anterior knee pain: the challenge of patellofemoral syndrome. Am Fam Physician 1993;47:185-94.
Pathology: da disease of the articular cartilage. Continuing mechanical stimulation follows by an initial increase in water and cartilage thickness. Gradual loss of proteoglycans and ground substance. Fissuring/splitting. Chondrocytes are damaged and release enzymes into the joint. Cystic progression and further cartilage loss. Subchondral bone is denuded and exposed to mechanical stresses. It becomes hypervascular forming osteophytes. Subchondral cysts and bone thickening/sclerosis develop.
Imaging plays a crucial role in Dx/grading and management
Clinically: pain on walking/rest, crepitus, swelling d/t synovitis, locking/catching d/t osseocartilaginous fragments and gradual functional loss. Knee OA typically presents as mono and oligoarthritis. DDx: morning pain/stiffness is >30-min DDx from inflammatory arthritis
Treatment: in mild to moderate cases-conservative care. Severe OA-total knee arthroplasty
Grade 4: severe JSN, large osteophytes, marked subchondral sclerosis and definite bony deformity
Typical report language will state:
Minor, mild, moderate or severe aka advanced arthrosis
Technique
Radiography: AP weight-bearing knees: note severe JSN of the medial compartment more severely with lateral knee compartment. Osteophytes and marked genu varum deformity and bone deformation
Typically medial femorotibial compartment is affected early and more severely
The patellofemoral compartment is also affected and best visualized on the lateral and Sunrise views
Impressions: severe tri-compartmental knee arthrosis
Recommendations: referral to the orthopedic surgeon
Moderate JSN
B/L AP weight-bearing view (above top image): Moderate JSN primarily of the medial femorotibial compartment. Osteophytosis, subchondral sclerosis and mild bone deformation (genu varum)
May present as asymptomatic chondrocalcinosis, CPPD arthropathy resembling DJD with pan predominance of large subchondral cysts. Often found as isolated PFJ DJD
Pseudogout with an acute attack of knee pain resembling gouty arthritis
Radiography is the 1st step and often reveals the Dx
Arthrocentesis with polarized microscopy may be helpful to DDx between CPPD and Gouty arthritis
Rheumatoid Arthritis
RA: an autoimmune systemic inflammatory disease that targets soft tissues of joints synovium, tendons/ligaments, bursae and extra-articular sites (e.g., eyes, lungs, cardiovascular system)
RA is the m/c inflammatory arthritis, 3% of women and 1% of men. Age: 30-50 F>M 3:1, but may develop at any age. True RA is uncommon in children and should not be confused with Juvenile Idiopathic Arthritis
RA most often affects small joints of the hands and feet as symmetrical arthritis (2nd 3rd MCP, 3rd PIPs, wrists & MTPs, sparing DIPs of fingers and toes)
Radiographically: RA presents with joint effusion leading to hyperemia and marginal erosions and periarticular osteoporosis. In the knee, the lateral compartment is affected more frequently leading to valgus deformity. Uniform aka concentric/symmetrical JSN affects all compartments and remains a key Dx clue
An absence of subchondral sclerosis and osteophytes. Popliteal cyst�(Baker’s cyst) may represent synovial pannus and inflammatory synovitis extending into the popliteal region that may rapture and extend into posterior leg compartment
N.B. Following initial RA joint destruction, it is not unusual to note superimposed 2nd OA
Radiography is the 1st step but early joint involvement may be undetectable by x-rays and can be helped by US and/or MRI.
Final Dx is based on Hx, clinical exam, labs, and radiology
Clinical pearls: patients with RA may present with a single knee being affected
Most patients are likely to have bilateral symmetrical hands/feet RA.
Cervical spine, particularly C1-2 is affected in 75-90% of cases throughout the course of the disease
N.B. Sudden exacerbation of joint pain in RA should not underestimate septic arthritis because patients with pre-existing RA are at higher risk of infectious arthritis. Joint aspiration may help with Dx.
Radiographic DDx
RA (above left) vs. OA (above right)
RA: concentric (uniform) joint space loss, lack of osteophytes and juxta-articular osteopenia.
Clinical Pearls: patients with RA may present radiographically with subchondral sclerosis d/t superimposed DJD. The latter feature should not be interpreted as OA but instead considered as secondary OA
AP Knee Radiograph
Note marked uniform JSN, juxta-articular osteopenia and subchondral cystic changes
Clinical Pearls: subcortical cysts in RA will characteristically lack sclerotic rim noted in OA-associated subcortical cysts.
MRI Sensitivity
MRI is very sensitive and may aid during early Dx of RA.
T2 fat-sat or STIR and T1 + C gad contrast fat-suppressed sequences may be included
MRI Dx of RA: synovial inflammation/effusion, synovial hyperplasia, and pannus formation decreased cartilage thickness, subchondral cysts, and bone erosions
MRI is very sensitive to reveal juxt-articular bone marrow edema, a precursor to erosions
Intra-articular fibrinoid fragments known as “Rice bodies” are characteristic MR sign of RA
Note: T2 fat-sat sagittal MRI revealing large inflammatory joint effusion and pannus synovial proliferation (above arrowheads). No evidence of radiographic or MRI bone erosions present. Dx: RA
STIR MR Slices
Note: STIR MR slices in the axial (above bottom image) and coronal planes (above top image) demonstrate extensive synovitis/effusion (above arrowheads) and multiple erosions in the medial and lateral tibial plateau (above arrows)
Additionally, scattered patchy areas of bone marrow edema are noted (above asterisks) such marrow edema changes are indicative and predictive of future osseous erosions.
Additional features: note thinning and destruction of joint cartilage
Bone neoplasms and tumor-like conditions affecting the knee can be benign or malignant. Age at Dx is crucial for DDx
In patients <40: Benign bone neoplasms: Osteochondroma, Enchondroma are relatively frequent
Fibrous cortical defect (FCD) & Non-ossifying fibroma (NOF) are particularly frequent in children
Giant cell tumor (GCT) is the m/c benign neoplasm of the knee in patients between 20-40 years of age
Malignant bone neoplasms in <40: m/c Osteosarcoma and 2nd m/c Ewing sarcoma
In patients >40: malignant neoplasms: m/c are secondaries d/t bone metastasis. Primary bone malignancy:�the m/c
Multiple Myeloma (MM). Less frequently:�a 2nd�peak of Osteosarcoma (post-radiation or Paget�s), Fibrosarcoma or Malignant�Fibrous�Histiocytoma�(MFH) of bone.
Clinically: knee pain, pathological fracture
Some tumor-like conditions like FCD/Non-ossifying fibroma are asymptomatic and may regress spontaneously. Occasionally NOF may present with pathologic fracture. N.B. any knee/bone pain in a child/adolescents should be�treated with clinical suspicion and adequately investigated.
Imaging: 1st step: radiography
MRI with T1+C is crucial for lesion characterization/regional extent, staging and pre-operative planning. CT may�help with pathologic Fxs detection. If malignant bone neoplasms considered, CXR/CT, PET-CT to investigate�metastatic spread and staging are important
Imaging Approach Bone Neoplasms
Approach to imaging Dx of bone neoplasms includes age, bone location (epiphysis vs. metaphysis vs. diaphysis), zone of transition surrounding the lesion, periosteal response, type of matrix, permeating or moth-eaten destruction vs. sclerotic, ground-glass, osteoid, cartilaginous matrix, soft tissue invasion, etc.
Key x-radiography features to DDx benign vs. malignant bone neoplasm:
Zone of transition: lesion is geographic with a narrow zone of transition vs. ill-defined wide zone of transition suggesting aggressive bone resorption
What type of bone destruction occurred: soap-bubbly appearance vs. osteolytic vs. osteosclerotic changes
Is there a round-glass matrix? Is there a well-defined rim of the sclerotic border with septations potentially suggesting slow growth and encapsulation like most benign processes.
Periosteal proliferation: solid vs. aggressive spiculated/sunburst/hair-on-end with local soft tissue invasion and Codman triangle (study next slide)
FCD & NOF
FCD & NOF or more appropriately Fibroxanthoma of the bone are benign bone processes that m/c seen in children. DDx based on the size with FCD presenting as <3-cm and NOF >3cm lesion composed of a fibrous heterogeneous matrix. FCD are asymptomatic and may regress in many cases. Some may progress to NOF. Location: identified in the knee region as an eccentric cortical based lesion.
FCD must be DDx from an avulsive irregularity d/t repeated stress along Linea aspera by extensors muscles
Dx: radiography
Management: leave-me-alone lesion. Occasionally NOF may progress and lead to pathologic fracture requiring orthopedic consult
Osteochondroma
Osteochondroma: m/c benign bone neoplasm. Knee is the m/c location. Contains all bone elements with a cartilaginous cap. Presented as pedunculated or sessile bone exostosis pointing away from the joint.
1% malignant degeneration to chondrosarcoma if solitary lesion and 10-15% in cases of HME
Other complications: fracture (top left image) pseudoaneurysm of the Popliteal artery, adventitious bursa formation
Hereditary Multiple Exostosis (HME)– autosomal dominant process. Presents with multiple osteochondromas (sessile-type dominates). May lead to limb deformities (Madelung deformity, coxa valga) reactive ST pressure, malignant degeneration
Dx: radiography, MRI helps to Dx malignant degeneration to chondrosarcoma by changes in size and activity of cartilaginous cap (>2-cm in adults may manifest malignant degeneration). MRI will also help with Dx of regional complications
HME & Knee Pain
37-y.o male with HME and knee pain. Axial T1, T2 and STIR MRI slices at the popliteal region. Large cartilaginous cap and possible compression of the popliteal artery by osteochondroma. MRA was performed to evaluate popliteal A. pseudoaneurysm (large arrow). Pathology specimen obtained from the cartilaginous cap showed increased cellularity suggestive of malignant degeneration. Operative care was planned
Giant Cell Tumor (GCT) aka Osteoclastoma
GCT- is a relatively common primary benign bone neoplasm. Age 25-40. M>F slightly.
GCT is the M/C benign sacral tumor. In 50% of cases, GCT occurs about the knee.
GCT is histologically benign, but lung Mets may develop esp. if in distal radius and hands, often termed Malignant GCT
<1% unresponsive/recurring GCTs may undergo malignant transformation to high-grade bone sarcoma
Pathology: histologically composed of osteoclasts-multinucleated giant cells with stromal cells derived from precursors monocyte-macrophage type. Produces cytokines and osteolytic enzymes. GCT may contain blood and associated with secondary Aneurysmal Bone Cyst (ABC)
Clinically: knee pain unresponsive to conservative care. Pathologic Fx may occur
Imaging: always begins with radiography followed by MRI and surgical biopsy that are crucial to Dx.
Rx: operative with curettage and cementing, a surgical appliance may be used if pathological fx present and cortical breach. In more severe cases other options available
Radiologic-Pathologic Dx
Radiologic-pathologic Dx: osteolytic and soap-bubbly lesion typically involving metaphysis and into epiphysis (classic key feature) with subarticular extension. Zone of transition is generally narrow but occasionally in aggressive lesions wide zone of transition may be seen.
MRI: low T1, highT2/STIR, characteristic fluid-fluid levels noted that are present in GCT and ABC. Histology is crucial to Dx.
DDx: ABC, Brown cell tumor of HPT (osteoclastoma), Telangiectatic Osteosarcoma
Radiological rule: if the physeal growth plate is present Dx of GCT is taken off the list in favor of chondroblastoma and vice versa.
Primarily Soap-Bubbly Appearance of GCT
Coronal, Fat-Sat Sagittal & Axial MRI Slices of GCT
T1 coronal, T2 fat-sat sagittal and T2 axial MRI slices of GCT. Typically: low T1, highT2/STIR and fluid-fluid levels
Characteristic MRI Appearance of GCT
Fluid-fluid levels d/t different composition of blood degradation products
Important DDx: ABC
Malignant Neoplasms About the Knee
In children and very young adults, m/c primary malignant neoplasm is central aka intramedullary (osteogenic) osteosarcoma (OSA). Second peak of OS: >70 y.o d/t Paget�s (1%) and/or post radiation OSA.
The knee is the m/c location of OSA (distal femur, prox. Tibia)
A 2nd m/c malignant pediatric primary is Ewing sarcoma.
In adults >40 y.o. the m/c primary is Multiple Myeloma (MM) or Solitary Plasmacytoma
Overall m/c bone neoplasms in adults d/t bone Mets from lung, breast, prostate, renal cell, thyroid (discussed)
Dx: clinical and radiological with surgical biopsy
Imaging is crucial to Dx. 1st step x-radiography. MRI+ gad C is vital
CT scanning occasionally helps to evaluate pathological fracture
Central (Intramedullary) Osteosarcoma (OSA)
m/c age: 10-20. m/c location: knee, males>females. Increased risk in some
congenital syndromes and mutation of the retinoblastoma gene: Rothmund-Thompson AR syndrome.
Early Dx is important d/t 10-20% present with Lung Mets at Dx. Prognosis depends on stages. Early stages with local bone invasion and no
mets 76% of survival.
Rx: limb salvage procedures preferred with 8-12 weeks of chemo, amputation if encased neurovascular tissue, path Fx, etc.
Imaging: radiography and MRI.
Clinically: bone pain, Inc. Alkaline Phosphatase
Chest CT if lung Mets considered
Classic Rad Features of OSA
Osteoid forming a sclerotic mass with aggressive hair-on-end/speculated/sun-burst periosteal reaction, Codman’s triangle and soft tissue invasion. Order MRI for staging and extent. Chest CT is crucial for Lung Mets dx.
MRI is Crucial for Dx/Staging
Note sagittal T1 (left) and STIR (right) MR slices: large mass extending from distal femoral metaphysis to remaining shaft. A low signal on T1 and high on STIR d/t marrow invasion with edema, hemorrhaging and tumor invasion. Local ST invasion seen (white arrows). Periosteal lifting and Codman�s triangle (green arrow) are additional signs of aggressive neoplasm.
Note an interesting feature that the epiphysis is spared d/t physeal plate serving temporarily as an additional barrier to the tumor spread.
Ewing Sarcoma
Ewing sarcoma: age: 2-20, uncommon in black patients. 2nd m/c highly malignant bone neoplasm in children that typically arises from medullary cavity (Round cell tumors). Key symptom: bone pain that may mimic infection (ESR/CRP/WBC) Considered PNET Key Rad Dx: aggressive moth-eaten/permeative lucent lesions in the shaft of long bones with sizeable soft tissue invasion/typical onion skin periostitis. May produce saucerisation May affect flat bones. May appear as sclerotic in 33%. Early lung Mets (25-30%) bone-to-bone Mets Poor prognosis if delayed Dx. Imaging steps: 1st step x-rad, MRI is v. important followed by a biopsy. CXR/CT PET-CT Rx: combined rad-chemo, operative.
Note aggressive expansile osteolytic lesion in the distal femur metaphysis into epiphysis. No periosteal reaction present. Following further work up with abdominal and chest CT scanning, Dx of Renal cell carcinoma was established
Distal Mets into lower extremity are more common with lung, renal cell, thyroid and breast CA.
Renal cell and Thyroid will typically present with aggressive osteolytic expansile mass aka �blowout Mets.�
In general, imaging approach should consist of Radiographic knee series, followed by MRI if x-rays are unrewarding
Tc99 Bone scintigraphy is the modality of choice to evaluate metastatic bone disease
Soft Tissue Neoplasms About the Knee
Malignant fibrous histiocytoma (MFH) reclassified as Pleomorphic Undifferentiated Sarcoma (PUS) is the m/c S.T. sarcoma. MFH is aggressive biologically with poor prognosis M>F (1.2:1) 30-80 with a peak in a 6th decade. 25-40% of all adults sarcomas m/c extremities. Retroperitoneum next (worst prognosis d/t late Dx and large growth w/o symptoms) Clinically: painful, hard mass typically about the knee or thigh. Histology: poorly differentiated/undifferentiated malignant fibroblasts, myofibroblasts, and other mesenchymal cells Imaging: MRI is the modality of choice with T1, T2, T1+C. Typically appears as an aggressive heterogeneous mass intermediate to low signal on T1 and high signal on T2 with areas of necrosis and enhancement on T1+C. May appear misleadingly encapsulated w/o true capsule Management: operative with radiation and chemotherapy. Tumor depth is crucial for prognosis. 80% 5-year survival if <5cm deep in ST and 50% if >5-cm deep in ST.
Synovial Sarcoma
Synovial sarcoma: common malignant ST neoplasm esp. in younger patients or older children/adolescents. M/C found in knee area Clinically: can present slowly as a palpable mass in the extremity often ignored d/t slow growth Imaging is the key: radiography may reveal ST. density/mass. Some synovial sarcomas may show calcification and mistaken for Myositis Ossificanse or heterotopic bone formation MRI with T1, T2 and T1+C are Dx modality of choice. Other modalities: US, CT are non-specific DDx: MFH Management: operative, chemo-radiation Prognosis: variable depending on size, invasion, metastasis
Types, location, and stability of tears are v. important during MRI Dx
Vertical/longitudinal tears especially occur in acute ACL tears. Some longitudinal tears found at the periphery or “red zone” may heal
Bucket handle tear: longitudinal tear in the inner edge that is deep and vertical extending through the long axis and may displace into a notch
Oblique/flap/parrot-beak are complex tears
Radial tear at 90-degree to plateau
Axial T2
Axial T2 WI fat-sat and coronal STIR slices of the posterior horn of the medial meniscus.
Note a radial tear of the posterior horn of the medial meniscus near the meniscal root. This is potentially an unstable lesion requiring operative care
The meniscus, in this case, is unable to provide a “hoop-stress mechanism.”
MRI Slices Coronal & Sagittal
Fat-sat coronal and sagittal proton density MRI slices revealing horizontal (cleavage) tear that is more typical in the aged meniscus
In some cases, when this tear does not contain a radial component, it may partially heal obviating the need for operative care
T2 w GRE Sagittal MRI Slice
Complex tear with a horizontal oblique and radial component.
This type of tear is very unstable and in most cases may need operative care
Bucket Handle Tear
Bucket handle tear are m/c in the medial meniscus esp. with acute ACL and MCL tear
MRI signs; double PCL sign on sagittal slices
Absent “bow-tie” sign and others
Most cases require operative care
DDx From Meniscal Degeneration
Occasionally meniscal tears need to be DDx from meniscal degeneration which may also appear bright (high signal) on fluid-sensitive MRI
The simplest rule is that if there is a true meniscal tear aka Grade 3 lesion, it always reaches/extends to the tibial plateau surface
The Role of MSK Ultrasound (US) in Knee Examination
MSK US of the knee permits high resolution and dynamic imaging of primarily superficial anatomy (tendons, bursae, capsular ligaments)
MSK US cannot adequately evaluate cruciate ligaments and the menisci in their entirety
Thus MR imaging remains modality of choice
Potential Pathologies Successfully Evaluated by MSK US
Patellar tendionosis/patellar tendon rupture
Quadriceps tendon tear
Prepatellar bursitis
Infrapatellar bursitis
Pes Anserine bursitis
Popliteal cyst (Baker cyst)
Inflammation/joint effusion with synovial thickening and hyperemia can be imaged with US (e.g., RA) especially with the addition of color power Doppler
Patient Presented With Atraumatic Knee Pain & Swelling
Radiography revealed sizeable soft tissue density within the superficial pre-patella region along with mild-to-moderate OA
MSK US demonstrated large septated heterogeneous fluid collection with mild positive Doppler activity on the periphery indicating inflammation d/t Dx of Superficial pre-patella bursitis
Long Axis US Images
Note normal lateral meniscus and fibers of LCL (above bottom image) compared to
Horizontal degenerative cleavage tear along with protrusion of lateral meniscus and LCL bulging (above top image)
Major limitation: unable to visualize the entire meniscus and the ACL/PCL
MRI referral is suggested
Rupture of Distal Tendon of Quadriceps
Note rupture of distal tendon of the Quadriceps muscle presented as fiber separation and fluid (hypo to anechoic) fluid collection within the substance of the tendon
Advantages of MSK US over MRI to evaluate superficial structures:
Dynamic imaging
Availability
Cost-effective
Patient’s preparation
Disadvantages: limited depth of structures, inability to evaluated bone and cartilage, etc.
Osteochondral Knee Injuries (OI)
osteochondral knee injuries can occur in children 10-15 y.o presented as Osteochondritis Dissecance (OCD) and in mature skeleton m/c following hyperextension and rotation trauma, particularly in ACL tear.
OCD-typically develops from repeated forces in immature bone and affects m/c postero-lateral portion of the medial femoral condyle.
OI in mature bone occurs m/c during ACL tears mainly affecting so-called terminal sulcus of the lateral femoral condyle at the junction of the weight-bearing portion opposed to tibial plateau and the part articulating with the patella
Osteochondral injuries may potentially damage the articular cartilage causing secondary OA. Thus need to be evaluated surgically
Imaging plays an important role and should begin with radiography often followed by MR imaging and orthopedic referral.
OCD Knee
95% associated with some trauma. Other etiology: ischemic bone necrosis especially in adults
Other common location for osteochondral injuries: elbow (capitellum), talus
1st step: radiography may detect osteochondral fragment potentially attached or detached
Location: a posterior-lateral aspect of the medial femoral condyle. Tunnel (intercondylar notch) view is crucial
MRI: modality of choice >90% specificity and sensitivity. Crucial for further management. T1-low signal demarcating line with T2 high signal demarcating line that signifies detachment and unlikely healing. Refer to orthopedic surgeon
Management: stable lesion esp. in younger children>off weight-bearing-heals in 50-75%
Unstable lesion and older child or impending physeal closure>operative fixation.
Result from valgus or varus stress with or w/o axial loading
Associated with periarticular soft tissues injury
High-stress injury m/c due to jumps falls and axial loading, often with the splitting of the tibial plateau. Men>women. Patients are in their 30s
Low impact or no trauma in patients with osteoporosis d/t insufficiency fractures
Impaction injury is more common with depression of tibial plateau. Women>men. Patients are in their 70s
Lateral Tibial Plateau Fractures More Common
Functional anatomy plays a significant role
60% of weight bearing is by the medial plateau
The medial plateau is more concave
Lateral plateau is slightly higher and more convex. Valgus stress impacts lateral plateau.
Tibial plateau fractures considered intra-articular and prone to delayed healing, non-union, meniscal injury (m/c lateral) ACL tear, secondary OA. Other complications: compartment syndrome, vascular injury.
Management: operative in many cases especially if >3-mm step-off at the plateau
If medial plateau or bicondylar Fxs present, ORIF will be required.
Imaging Plays A Crucial Role
Begins with x-radiography. X-radiography may not reveal the complexity and extent of this injury.
CT scanning w/o contrast will further delineate fracture complexity and pre-operative planning
MR imaging may be considered to evaluate for internal derangement: meniscal, ACL injuries.
Shatzke classification may help to evaluate the complexity of this injury
Key Diagnostic Sign
AP and lateral horizontal beam (cross table) left knee radiograph. Note subtle depression of the lateral plateau manifested by the lateral plateau appearing at the same level or lower as the medial. A critical diagnostic sign is the presence of fat-blood-interphase or FBI sign on cross-table lateral (above arrow) indicating intra-articular knee fracture
Lipohemarthorosis aka FBI Sign
Can be detected by radiography, CT or MR imaging
FBI sign is a reliable secondary radiographic sign of intra-articular knee fractures, regardless of how small they are
Mechanism: fracture results with acute hemarthrosis
Hemarthrosis will also occur w/o Fx. However, Fx will result with a fatty marrow being released into the joint cavity. Fat is a less dense medium (lighter) and will appear on the top of the hemorrhage if the patient is held in the supine position for 5-10-minutes before the cross-table radiograph is taken
FBI sign confirms the intra-articular Fx.
ACL/PCL, meniscal tears will not result in FBI sign
Lateral Tibial Plateau Fx
Lateral tibial plateau Fx that was managed operatively
Most common complication: premature secondary OA
More complex injuries may result in more extensive operative care
Knee Internal Derangement
Acute or chronic injuries of meniscal fibrocartilages and ligamentous restraints
Tears of the ACL and posterior horn of the medial meniscus are the most common
Acute ACL tears, however, often result with a lateral meniscus tear
Acute ACL tear may occur as a combined injury of the ACL, MCL, and medial meniscus
Functional anatomy: ACL prevents anterior displacement of the tibia and secondary varus stress
MCL functions together with ACL in resisting external rotation of the tibia especially when the foot is planted (closed chain position)
MCL is firmly attached to the medial meniscus, explaining the classic triad of ACL, MCL and medial meniscal tear (O’Donahue terrible triad)
Cruciate ligaments (ACL/PCL) are intra-articular but extra-synovial. Less likely to be torn in closed pack position (full extension). When all articular facets of tibia and femur are in full contact, the ACL/PCL are at least tension and stable
When the knee is flexed 20-30-degrees or more ACL is taut and remains unstable
ACL is a significant mechanoreceptor that feeds the info to CNS about the joint position. Thus the majority of previous ACL tears will lead to some degree of knee instability
Functional Anatomy of ACL
Diagnosis of ACL Tear
Diagnosis of ACL tear requires MR imaging
Concerns exist of not only ligamentous injuries but injuries to the articular cartilage and menisci.
Most vendors will perform at least: one T1 WI in coronal or sagittal planes. Sagittal and coronal Proton-density slices to evaluate cartilaginous structures. Fast spin-echo sagittal, axial and coronal T2 fat-saturated or sagittal and coronal STIR images are crucial to demonstrate edema within the substance of knee ligaments
ACL is aligned along the Blumensaat line or oblique line corresponding the intercondylar roof of Femoral condyles. Lack of such alignment by the ACL is significant for ACL tear
Imaging Dx of Internal Derangement
MRI shows 78-100% sensitivity and 78-100% specificity
Primary signs of ACL tear: non-visualization of ACL (above green arrow), loss of its axis along the Blumensaat line (above triangle heads), wavy appearance and substance tear (above white arrow) or edema and cloud-like indistinctness (above yellow arrow)
Reliable Secondary Signs of ACL Tear
May be observed on the radiographs and MRI
Segond avulsion fracture (80% specificity for ACL tear) (next slide)
Deep femoral notch sign indicating osteochondral fracture (above bottom images) and
Pivot -shift bone marrow edema in the posterolateral tibial condyle d/t external rotation and often valgus impact by the lateral femoral condyles (above top image)
Segond Fracture (Avulsion by ITB)
Segond fracture at Gerdy’s tubercle. A vital sign of the ACL tear seen on both radiographs and MRI
Management of ACL Tears
In acute cases, usually operative using cadaveric or autograft (patella ligament or hamstring) ACL reconstruction
Complications: graft tear, instability and premature DJD, joint stiffness d/t lack of postoperative rehab or gaft shortening. More rare, infection, a formation of intraosseous synovial cysts, etc.
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