Intraarticular fibroma of tendon sheath.

A 17-year-old male presented to us following a hyperflexion injury to his right knee sustained while playing soccer. Immediately after the traumatic event, he developed a large, tense knee effusion. Physical examination revealed limited range of motion. MRI revealed a lobulated mass in the posteromedial aspect of the knee joint. The mass was excised and sections submitted to pathology. A pathologic, microscopic, and immunohistochemical characteristics revealed the final diagnosis of fibroma of tendon sheath in the knee. At 12 months followup, the patient reported no subjective symptoms, such as pain or limitation of athletic activities and has full range of motion. Additionally, he has demonstrated no signs of recurrence. We report a case of fibroma of the tendon sheath originating from the synovial membrane of the joint capsule of the knee. [ABSTRACT FROM AUTHOR]