Identical osteochondritis dissecans lesions of the knee in sets of monozygotic twins.

Osteochondritis dissecans (OCD) is a focal, idiopathic alteration of subchondral bone structure with the risk for secondary damage to adjacent articular cartilage and the development of premature osteoarthritis. The exact etiology of OCD is unknown, although repetitive microtrauma and vascular insufficiency have been previously described. A genetic predisposition has been suggested, but the existing evidence is sparse. There are multiple case reports of twins and siblings with OCD and a few large family series in the literature, promoting the theory that OCD may have a genetic component to its etiology. This article describes 2 sets of monozygotic twins presenting concurrently with OCD of their dominant knees, offering further support for a genetic component to the etiology of OCD. Interestingly, in both sets of twins, 1 was left-handed and 1 was right-handed. Both sets of twins had simultaneous presentations and clinical courses, lending support to a genetic element to OCD. The development of the OCD lesion in the dominant knee of each patient suggests an environmental influence, perhaps due to repetitive microtrauma and overuse. Recently, a genome-wide linkage study identified a prime candidate locus for OCD. However, despite the suggested association, genetic and developmental factors in the development of OCD remain relatively unstudied. The authors believe monozygotic twins provide an excellent clinical opportunity for future examination of the role of familial inheritance in the etiology of OCD.