This disorder is characterized by well-localized pain when the patella is grated against the femoral condyles or when the knee is actively extended with the patella manually displaced distally. Rubacky (1963) described 5 families with multiple affected persons ... This disorder is characterized by well-localized pain when the patella is grated against the femoral condyles or when the knee is actively extended with the patella manually displaced distally. Rubacky (1963) described 5 families with multiple affected persons in multiple generations and male-to-male transmission. The association of patellar chondromalacia with recurrent dislocation of the patella (169000) is well known and the former is usually attributed to the latter. However, Rubacky (1963) suggested that the cause and effect relation may be the other way around in some cases. This condition is probably not a form of osteochondritis dissecans (165800), which can affect the patella.