A 24-year-old man complains of progressive intermittent claudication of the left leg. On examination, the popliteal, dorsalis pedis, and posterior tibial pulses are normal; but they disappear on dorsiflexion of the foot. What is the most likely diagnosis?

Popliteal artery entrapment syndrome consists of intermittent claudication caused by an abnormal relation of that artery to the muscles, usually the medial head of the gastrocnemius muscle. As a consequence of developmental abnormalities, the popliteal artery may be compressed by the medial head of the gastrocnemius muscle, resulting in ischemia of the leg at an unusually early age. On examination, the pulses may be diminished or absent, but they may also be normal and be made to disappear on dorsiflexion of the foot. Angiography is essential to establish the diagnosis.