This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Arterial Disorders, Subject name: Surgery
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? 
Select and explain. 
A. Embolic occlusion, B. Thromboangiitis obliterans, C. Atherosclerosis obliterans, D. Popliteal artery entrapment syndrome
D: Popliteal artery entrapment syndrome
Answer: D: Popliteal artery entrapment syndrome 
Explanation: 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.