A probable cause of popliteal artery entrapment is proposed. The medial head of the gastrocnemius muscle during its embryological development crosses the popliteal fossa from lateral to medial. It is proposed that the migrating medial head carries the popliteal artery and vein across the fossa and entraps them against the medial condyle of the femur. Dissection of 86 anatomical specimens revealed two cases of unilateral and one case of bilateral entrapment of both popliteal vessels. Two surgical cases of popliteal entrapment are presented. This entrapment syndrome is a remedial cause of claudication and when considered, it is readily diagnosed and surgical correction is effective. Because of distal embolisation and occlusions, early recognition and treatment is desirable. Forty-seven cases from the literature are reviewed as to the entrapment type and the age and sex of the patients.