Glomus tumor beneath the plica synovialis in the knee: a case report.

Glomus tumors are rare benign tumors distinguished clinically by their small size and ability to cause extreme pain. These lesions are usually found beneath the fingernails. Atypical locations of the tumor are difficult to diagnose, especially when the lesion is situated in a deep anatomic structure. We describe a 33-year-old man with glomus tumor beneath the plica synovialis in the knee. He had experienced right knee pain for 10 years which increased with movements of the knee. There was a point of tenderness on palpation at the lateral aspect of the knee. CT scan with arthrography showed a small mass on the lateral femoral condyle in the joint space. It was seen retrospectively in MRI. Arthroscopy demonstrated the soft tissue mass beneath the plica synovialis. We made a separate incision and removed it completely. An immediate disappearance of the pain was observed after surgery. Histology was the glomus tumor of the vascular type. The tumor seemed to be stimulated by the plica synovitis or the lateral joint capsule and it caused pain on motion similar to meniscal tear. There has been no recurrence for 3 years after surgery.