Juvenile osteochondritis dissecans of the knee: predictors of lesion stability.

BACKGROUND Recent data suggest magnetic resonance imaging (MRI) is the best method to analyze the status of the cartilage and subchondral bone in patients with juvenile osteochondritis dissecans (JOCD). METHODS MRI analysis of 122 knees and 132 JOCD lesions in 109 patients who underwent arthroscopic treatment for osteochondritis dissecans lesions of the knee between March 2003 and January 2011. RESULTS Agreement between MRI and arthroscopic grading was 62.1%. MRI sensitivity was 92% and specificity was 55%. Positive predictive value of MRI was 33% and negative predictive value of MRI was 97%. In a multivariable logistic regression model, the odds of a unstable lesion on the lateral femoral condyle nonweight-bearing location were 15.7 times greater than the odds of an unstable lesion on the medial femoral condyle weight-bearing area (95% confidence interval: 2.6-95.7, P=0.003.) The odds of the lateral femoral condyle weight-bearing lesion having an unstable grade were also greater than for a medial femoral condyle weight-bearing lesion, but the results were not statistically significant (odds ratio, 1.70, P=0.349). CONCLUSIONS A high T2 signal retrograde to the lesion may commonly appear with an early, stable arthroscopic grade lesion. MRI continues to be reliably sensitive to JOCD lesions and a good predictor of low-grade, stable lesions. However, MRI predictability of high-grade, unstable JOCD lesions is less reliable. Lesions in atypical locations, such as the nonweight-bearing surface of the lateral femoral condyle, more commonly present as higher, arthroscopic grade lesions. LEVEL OF EVIDENCE Level IV, retrospective case series.