When to suspect chronic exertional compartment syndrome
Leg pain in CECS results from increased pressure within the lower extremity fascial compartments temporally related to exercise.2,23,24 Its incidence in the general population is unknown, but CECS has been found to range from 14% to 27% in patients with previously undiagnosed leg pain1,14,25 and to affect about a third of athletes with chronic ELP. In addition, CECS has been found in 90% of patients who have both diabetes and ELP with normal findings on vascular studies.1,3,4,26
The anterior compartment is most commonly affected, followed by the lateral, deep posterior, and superficial posterior compartments.3,13,23,27 Symptoms are bilateral 60% to 95% of the time.2,13,14,25 Factors contributing to CECS include fixed muscular compartment constraints, muscle swelling, thickened fascia, muscle hypertrophy related to resistance training, dynamic muscular contraction patterns, and low muscle capillary supply. Stretching of fascial pain receptors and pressure fibers and inadequate myocyte response to increased metabolism may play a role, as well.14,28
The initial clinical presentation is usually predictable leg pain—ie, pain that begins at about the same time, distance, or intensity of a workout and resolves with rest; numbness and weakness may occur as the workout progresses. In time, leg pain associated with CECS may be present with everyday activity or at rest. The physical exam may be normal or reveal swelling, tenderness over the involved compartments, pain with passive digit or ankle motion, and palpable muscle herniation.14
Measurement of intracompartmental pressure before and after exercise is the gold standard for diagnosis of CECS.2,14,27 Pre-exercise values ≥15 mm Hg and post-exercise values ≥30 mm Hg at one minute or ≥20 mm Hg at 5 minutes are all considered diagnostic of CECS,11 although these widely accepted criteria for bilateral testing of all compartments yields a false-positive rate of 5%.27 CECS is almost always bilateral,29 and some clinicians advocate limiting the number of needle insertions by taking only post-exercise measurements and testing only symptomatic compartments in one limb.
Imaging has limited value, as both x-rays and MRIs are usually normal.14 However, post-exertional T2-weighted MRI findings of muscular edema correspond to increased intracompartmental pressures, with a sensitivity of 87% and a specificity of 62%.14,24,30,31 Infrared spectroscopy, which measures levels of oxygenated and deoxygenated blood, is sensitive for CECS when the post-exercise ratio of deoxygenated to oxygenated blood remains elevated.14,24 Neither of these screening modalities is routinely obtained or considered diagnostic, however. Their chief role is to exclude an alternative diagnosis.14
Treatment and symptom relief. Discontinuing or modifying the aggravating activity typically brings relief of CECS. But this is not a long-term solution, as symptoms are likely to recur when the patient returns to the activity in question.1 The definitive treatment is compartment release via fasciotomy. Success rates for anterior and lateral compartment releases are >80%.1,28 The success of fasciotomy of posterior compartments, however, is <50%—a finding attributed to more complex anatomy, difficult visualization, and the presence of additional compartments.1,32
When the cause is vascular
Arterial endofibrosis—the fibrotic thickening of the intima of an artery—is thought to be caused by repetitive hip flexion.8 This results in hyperplasia, wall thickening, and eventual stenosis of the vessel, with 90% of cases affecting the external iliac artery.8,33 The condition is most common in activities such as cycling, but is also seen in such activities as running, skiing, soccer, and rugby. Symptoms are typically unilateral, but an estimated 15% of patients experience bilateral symptoms.8,33
Loss of power in the affected leg, with intermittent claudication and pain due to presumed ischemia from the vascular defect, is the usual presentation, although some patients develop cramping of the buttocks and/or paresthesia of the affected leg and foot during uphill running or cycling.8,33 The physical exam is often normal, but there may be a post-exercise arterial bruit over the femoral artery when the hip is flexed.8,34
Pre-exercise ankle-brachial index (ABI) <0.5 and post-exercise ABI <0.66 at one minute is suggestive of moderate arterial endofibrosis, with 90% sensitivity and 87% specificity.8,33,34 Arterial ultrasound and color Doppler may also be used for diagnosis, but are often operator dependent. Magnetic resonance angiography (MRA), while more expensive, can detect excessive kinking or compression of the vessel and is not operator dependent.8,33 Angioplastic balloon catheter dilation and stenting, bypass surgery, vascular reconstruction and endarterectomy with vein patch are the options for treatment. The success rates of the various interventions are unknown due to a lack of head-to-head studies and long-term follow-up.8,33
Popliteal artery entrapment syndrome (PAES) is a constellation of symptoms caused by vascular impingement in the popliteal fossa of the knee.8,34 The typical presenting symptoms are lower limb ischemia and pain caused by intense exercise that resolves quickly afterwards. Symptoms correlate more with the intensity than the duration of exercise.3,8
PAES is usually caused by a variant of the gastrocnemius muscle in which a medial head passes behind the popliteal artery in males younger than 30 years.8,33-35 Less commonly, it is the result of an overuse or acute orthopedic injury that irritates structures surrounding the popliteal fossa.8,34 PAES affects football, basketball, and soccer players, as well as runners because of excessive dorsiflexion and plantar flexion of the ankle.3,4
The physical exam for a patient with PAES is typically normal, but a post-exercise popliteal bruit with weak peripheral pulses may be elicited.8,33 An ABI in the neutral, forced dorsiflexion and forced plantar flexion positions can serve as a useful screening tool. An ABI <0.9 is abnormal, with a sensitivity and specificity of 90% and 98%, respectively, for stenosis >50%.2,36
Arteriography is the gold standard for diagnosis of PAES. Contrast arteriography is most commonly used because of its availability and cost. But MRA better differentiates functional from anatomic entrapment—a differentiation that less invasive tests, such as duplex ultrasound studies, lack the specificity to reveal.8,34 Treatment requires either surgical removal of the offending musculotendinous structures or arterial bypass and grafting of the chronically impinged area, as conservative therapies lack efficacy.2,8,34
Cystic adventitial disease (CAD) is the narrowing of an artery by mucoid cysts in the arterial wall or adventitia.8,9 It is a rare condition, accounting for just 0.1% of all vascular diseases, most commonly occurring in men in their mid-40s.8,33 CAD is thought to be the result of mucin-producing cells being haphazardly incorporated into the adventitia during arterial development. About 85% of patients whose popliteal artery is affected in this way will experience intermittent claudication with activity.8,9
On exam, such patients often have diminished ankle-brachial pressure indices, and duplex ultrasound often reveals stenosis in the affected artery, as well as a collection of mucoid cysts in the adventitia.8,9
Diagnosis can be confirmed by MRA.8,37 Evidence for the treatment of CAD is largely anecdotal.9 Cysts may be aspirated but tend to recur, and stenting does not correct the cystic-induced narrowing of the vessel. Surgical removal of the cysts is the only successful treatment.8,9