Osteochondritis dissecans: a histologic and microradiographic analysis of surgically excised lesions.

The excised fragments of six osteochondritis dissecans lesions of the lateral aspect of the medial femoral condyle were found to be composed of viable hyaline articular cartilage over-lying a totally cellular, metabolically active ossific nucleus, which in turn rested in a bed of fibrocartilage. At the interface between the fibrocartilage and the bone, enchondral ossification was seen histologically and verified by microradiographic evidence of bone formation and resorption. The present authors propose that this classical dissecans lesion is a reparative process and, in most cases, will proceed to complete union of the ossific nucleus with the remainder of the bone of the femoral condyle.