A 26-year old male, who is a long-distance runner, presents to his doctor complaining of right foot pain during aerobic exercise in the last two months. He says that the pain exacerbates with training and he is now unable to tolerate even mild aerobic exercise. He is afraid that he will not be able to participate in the upcoming annual marathon scheduled for next month in his city, due to his frustrating symptoms. Further evaluation reveals that pain of his right foot is accompanied by right calf tightness, paresthesia and it is reproduced after running less than 100 meters. The pain is relieved within seconds to minutes after cessation of exercise. Occasionally when he drives his car for a long time, he feels numbness and coldness at his calf. He has noticed that these symptoms are produced with knee extension when the foot is plantar flexed. Last month he visited an orthopedic surgeon, who prescribed him analgesics and recommended physical therapy. However, despite the patient's adherence to medical instructions, the pain has not subsided. His last month knee MRI was unremarkable. Physical exam reveals patent femoral, popliteal and dorsal foot arteries and normal ankle-brachial-index (ABI). Pain is not reproduced with palpation, but it is elicited with sustained passive dorsiflexion and plantarflexion of the foot. The patient does not smoke and drinks alcohol only on weekends. There is no family history for cardiovascular diseases and his BMI is 25. He is a vegetarian and consumes protein supplements.
Which of the following is the most likely diagnosis?
Show Answer
The correct answer is: B. Popliteal artery entrapment syndrome
This patient's pain with exertion accompanied by paresthesia and coldness indicates a vascular abnormality. Indeed, this pain reproduction with certain movements is consistent with intermittent arterial occlusion, since symptoms diminish when normal arterial blood flow is reestablished at rest. Calf claudication radiating to the foot and reproduction of symptoms with sustained passive dorsiflexion and plantarflexion of the foot suggests popliteal artery entrapment syndrome (PAES).1 Onset of his symptoms during long-hour driving (requires plantarflexion) also indicates this diagnosis.1,2
PAES is a rare syndrome caused by external compression of popliteal artery by muscular or tendinous components.1 It is categorized mainly in two variants: anatomical and functional PAES. Anatomical PAES is associated with abnormal positioning of the popliteal artery and the medial head of gastrocnemius, due to developmental defects.1,2 Functional PAES is associated with hypertrophy of gastrocnemius and subsequent compression of popliteal artery.2 Patients with functional PAES are usually young athletes, especially runners who complain about symptoms that come and go, while exercising.2 Certain maneuvers during physical exam can reproduce the symptoms associated with PAES.1 The clinicians should raise a high suspicion for PAES as it can be difficult to differentiate it from other causes of exercise leg pain.1
When history and physical exam guide towards the diagnosis, an ABI should be estimated. ABI is usually normal in functional PAES because impingement is noted only during certain movements. PAES investigation also includes the use of doppler ultrasonography.1 The diagnosis is supported by patency of popliteal artery during rest and abnormal blood flow with certain maneuvers (i.e. plantarflexion, dorsiflexion).1 Computed tomography (CT) angiography and magnetic resonance angiogram (MRA) can also be considered in diagnostic evaluation. Magnetic resonance imaging (MRI) can reveal anatomic details and rule out other causes. Treatment options include surgical decompression of popliteal artery with or without performance of bypass in case of complete, permanent occlusion of the popliteal artery.1 In functional PAES, an alternative therapy could be botulinum toxin injections in muscular components surrounding the popliteal artery through ultrasound guidance.1
(Answer A) Although stress fractures are common in athletes, pain is locally distributed and usually is reproduced with palpation. Furthermore, tibia is usually the involved bone, so this patient's pain location would be atypical for a stress fracture.
(Answer C) Chronic exertional compartment syndrome (CECS) affects young athletes and presents with burning pain in a compartment of the leg during exercise.1 This patient's calf pain with foot radiation and reproduction with certain maneuvers is more likely associated with PEAS.1 Furthermore, pain of CECS usually subsides more gradually than the pain of PEAS which immediately improves after cessation of exercise. This patient's pain is relieved within seconds to minutes of rest.
(Answer D) Although atherosclerotic disease can provoke signs of ischemia in an affected leg, this young healthy adult has no established risk factors for developing atherosclerotic disease.
(Answer E) Cystic adventitial disease can present with intermittent occlusive vascular symptoms in healthy adults and it is typically associated with Ishikawa's sign (disappearance of foot pulses with knee flexion), which is absent in this patient.
Educational Objective
Popliteal artery entrapment syndrome should be suspected in otherwise healthy young athletes who experience calf claudication or other symptoms mimicking arterial occlusion during exercise. Immediate relief with rest, reproduction of symptoms and abnormal doppler ultrasound findings with certain maneuvers are diagnostic clues to differentiate it from other causes of exercise leg pain.
References
Hislop M, Kennedy D, Cramp B, Dhupelia S. Functional popliteal artery entrapment syndrome: poorly understood and frequently missed? A review of clinical features, appropriate investigations, and treatment options. J Sport Med 2014;105953:1-8
Turnipseed WD. Popliteal entrapment in runners. Clin Sports Med 2012;31:321-28.
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