 Osteocondritis dissecans, or OCD, is a bone disease that wears away joints in the cartilage that covers them. It occurs most often in children and adolescents. While OCD has been documented and studied for nearly 150 years, researchers still don't know what causes it. Reporting in the American Journal of Sports Medicine, one group offers up new findings that point to at least one factor that surgeons should look out for. The team looked at radiographs of 61 knees of patients undergoing surgery for OCD. Those patients were just over 23 years old on average, and 77% of them were men. The researchers reviewed the radiographs for mechanical alignment, as previous studies have speculated that deformities due to malalignment contribute to OCD. What they found was that patients with OCD did in fact show signs of off-axis effects. Specifically, they observed that the location of OCD lesions correlated with the deviation of the mechanical axis of the leg. Lesions on the lateral femoral condyle, one of two projections on the lower femur, tended to occur in patients with high values of the mechanical lateral distal femoral angle. That angle describes how close or far apart patient knees appear to be. Despite that link, the team found that the degree of deviation did not predict the size of OCD lesions. That suggests that, overall, abnormal mechanical alignment doesn't necessarily mean that OCD will occur. Other factors should, and likely do, contribute to the development or progression of OCD lesions. Still, the results are informative. As one of the first studies to examine OCD as a function of mechanical alignment, the report offers doctors at least one potentially important signal. With further work, researchers might uncover more telling signs that help treat or perhaps even prevent this debilitating bone disease.