Popliteal artery entrapment syndrome is an important, albeit infrequent, cause of severe disability among young adults and athletes with anomalous anatomic relationships of the musculotendinous structures surrounding the popliteal artery. We report a case where duplex ultrasonography and dynamic magnetic resonance arteriography was used to diagnose popliteal artery entrapment. We used a posterior surgical approach to give the best view of the anatomic structures compressing the popliteal artery. Compression had not yet damaged the arterial wall, therefore operative decompression of the artery by resection of the aberrant muscle was sufficient. The result was complete recovery, with absence of symptoms and with patency verified by Doppler examination. We conclude that emergency physicians who encounter young patients with progressive lower limb arterial insufficiency should be aware of the possibility of popliteal artery entrapment. Early diagnosis using physical examination, history taking, and imaging is necessary. The treatment of choice is surgical correction to achieve normal anatomy within the popliteal fossa.