Benign synovial disorders.

Collectively, benign synovial disorders are not uncommon, and they may be seen in general orthopaedic practices. Symptoms are nonspecific, often delaying diagnosis. In fact, synovial chondromatosis, pigmented villonodular synovitis, synovial hemangioma, and lipoma arborescens often mimic each other as well as other, more common joint disorders in presentation, making diagnosis extremely difficult. It is important to diagnose these disorders correctly in order to provide appropriate treatment and avoid secondary sequelae, such as bone erosion and cartilage degeneration.