Localized pigmented villonodular synovitis presenting as a loose body following minor trauma in the knee: a case report.

Localized pigmented villonodular synovitis (LPVS) is widely accepted to frequently develop symptoms resembling internal derangement in the knee, including limitation of motion and episodes of giving way and locking. We report the case of a 31-year-old man with LPVS displaying an unusual presentation. After sustaining a twisting injury to the knee, he suffered constant but subtle knee discomfort, sudden attacks of pain and a feeling of a loose body. Arthroscopic examination 1 month after injury revealed a freely mobile tumor in the supra-patellar pouch that was not pedunculated and displayed no soft tissue attachments to the synovium. Histological findings for the tumor were consistent with a diagnosis of LPVS. This case illustrates that LPVS may present with symptoms of a loose body after trauma to the knee.