Popliteal Artery Entrapment

Popliteal artery entrapment is due to compression of the popliteal artery by adjacent muscle, tendinous structures, or neural structures. Extrinsic arterial compression causes chronic vascular microtrauma, early arteriosclerosis, and thrombus formation and can lead to limb ischemia.

Popliteal artery entrapment can be classified into 6 types, with the caveat that not all causes are included in this classification.

• Type 1: Most common type. Normal medial head of the gastrocnemius muscle but abnormal medial course of the popliteal artery.
• Type 2: Abnormally lateral origin of the medial head of the gastrocnemius muscle.
• Type 3: Compression by an accessory strip of the medial head of the gastrocnemius muscle.
• Type 4: Compression by the popliteus muscle or branch of tibial nerve.
• Type 5: Any type with involvement of the popliteal vein.
• Type 6: Normal anatomy, but with functional compression of the popliteal artery due to hypertrophic muscles. Usually seen in well-conditioned athletes.

On angiography there is smooth narrowing of the popliteal artery. Medial deviation may also be seen. The contralateral leg must also be evaluated, as the anatomic abnormality may be bilateral in one third of cases.

Some patients have symptoms of popliteal artery entrapment without anatomic abnormality (type 6). In these patients, passive dorsiflexion or active plantar flexion of the ankle can induce narrowing of the popliteal artery due to hypertrophic muscles (usually the medial head of the gastrocnemius muscle). It must be noted that narrowing of the popliteal artery with passive dorsiflexion or active plantar flexion of the ankle can also be seen in asymptomatic patients with normal anatomy.

References

Elias DA, White LM, Rubenstein JD, Christakis M, Merchant N. Clinical evaluation and MR imaging features of popliteal artery entrapment and cystic adventitial disease. AJR Am J Roentgenol. 2003 Mar;180(3):627-32.