Meniscal ossicle: a case report.

Meniscal ossicle is a cortical or cancellous tissue with central viable marrow surrounded by meniscal cartilage. We present a case of medial meniscal ossicle at its posterior horn. A 21-year-old male military recruit visited our clinic due to left knee discomfort. He had not undergone any notable injury on the knee, but complained of intermittent catching or giving way without locking. Simple radiographs showed a small round bony fragment at posteromedial side of knee joint. The magnetic resonance imaging revealed an intra-substance lesion of meniscus, whose signal is identical to bone. On arthroscopy, the articular cartilage of medial femoral condyle and tibial plateau appeared degenerative with a groove-like scar. The medial meniscus seemed swollen at the posterior horn, but there was no discernible tear in the adjacent meniscus. After piecemeal removal of meniscal substance, a small osseous fragment was identified, which was evacuated via posteromedial portal. The resection of meniscus amounted to a subtotal meniscectomy. The activities of daily living were possible without any trouble even after 9 months of follow-up. This entity should be distinguished from intra-articular loose body, and included in the differential diagnosis of the incidental findings of small ossified density around knee joint.