An unusual case of vascular abnormality mimicking a lateral meniscal cyst.

An unusual case of a vascular abnormality mimicking a lateral meniscal cyst is reported. The patient was a 31-year-old active sportsman who presented with intermittent pain over the lateral aspect of the left knee joint line, occurring only during activities involving twisting motions such as playing soccer. He did not experience local tenderness or swelling, clicking, locking, or giving way. The magnetic resonance imaging, which was done after a diagnostic arthroscopy with normal intra-articular findings, showed a cyst formation of approximately 4-mm diameter adjacent to the lateral meniscus periphery, but no meniscal tissue degeneration. Exactly at the preoperatively marked site of most intensive pain sensation during twisting motions, surgical exposure showed a venous-aneurysm-like tumor, which was removed. The operation resulted in complete relief of symptoms and undisturbed sporting activities including soccer.