The knee is the most commonly affected joint; OCD affects the knee in 75% of cases, the elbow in 6% of cases, and the ankle in 4% of cases. In the knee, OCD involves the lateral aspect of the medial femoral condyle in 75% of cases, the weight-bearing surface of the medial condyle in 10% of cases, the weight-bearing surface of the lateral condyle in 10% of cases, and the anterior intercondylar groove or patella in 5% of cases.[5,12,13,14,15,16,17,18,19,20] Some authors underline that OCD of the talus is being diagnosed more frequently, as CT and MRI are becoming widely used and, in future series, may represent the most frequent site of OCD.
The symptoms of OCD include joint pain, crepitation, swelling, and stiffness. Symptoms may be aggravated with physical activities, such as playing sports. When a lower extremity is involved, patients often present with a limp. With complete fragment separation, locking symptoms may occur. Symptoms usually improve with protected immobilization of the joint. Clinical signs include effusion, tenderness over the lesion, quadriceps atrophy, and weakness. The patient may lack full knee extension when compared with the contralateral knee.
Occasionally, a loose body may be palpable. The Wilson test is sometimes performed as part of the examination of the knee when OCD is suspected. The examiner flexes the knee to 90° while internally rotating the tibia. A positive Wilson sign occurs when pain is elicited at 30° of flexion and is relieved with external rotation. However, one study found it to be of very little clinical value as 24 of 32 study patients with OCD lesions on x-rays had negative Wilson signs.
Several diagnostic methods are available for the diagnosis and staging of OCD, including plain films (anteroposterior, lateral, and notch/tunnel views), arthrography, ultrasonography, MRI (with or without gadolinium contrast), CT scanning, technetium bone scanning, and knee arthroscopy. Plain films may be normal early in the course. Notch views are the most effective view for evaluating the lateral aspect of the medial femoral condyle.
MRI is the best noninvasive imaging modality and can assess for lesion stability. Intra-articular gadolinium may improve lesion characterization.[16,22,23] CT can be performed if MRI is not available. Knee arthroscopy can be used both diagnostically and therapeutically.[3,4,20] Arthroscopic OCD stages are defined by the International Cartilage Repair Society. MRI has proven useful in evaluating lesion instability in adults but is less accurate in children.[25,26]
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