[Unusual location of osteochondral lesions in adolescent's knees].

Osteochondral knee lesions in adolescents are primarily located in loading areas at the level of the femoral condyles. Lesions located in the trochlea are exceptional and account for less than 1%. The etiology of juvenile osteochondritis dissecans (JOCD) is still unknown. Osteochondral lesions may be caused by direct frontal trauma of the femoral condyles and by direct trauma of the patella on the trochlea in dislocations of the latter. At this level both mechanisms may cause both chondral and osteochondral lesions. We present herein two cases with the same characteristics that include one patient with bilateral involvement of the trochlea. Arthroscopy was performed with removal of loose bodies, regularization of the bed and perforations, with appropriate long term results. Osteochondral lesions are rarely found in the trochlea; the literature contains very few bilateral cases described. The exact etiology of JOCD of the knee continues to be debated. In our cases the mechanism could be explained by a low-pressure high-speed impact of the patella on the trochlea. This type of lesions may be added to defects or abnormalities of ossification during childhood. The bilaterality of one of these cases would support this hypothesis. Treatment depends on lesion stability and patient age. Surgical treatment should be considered in patients with open physes with an un stable or detached lesion and in those in whom the physis is about to close but have not responded to conservative treatment, as well as in patients with an intraarticular loose body. Another point to consider is that insufficient fixation or fixation without a bone chip leads to mediocre results.