Chronic Exertional Compartment Syndrome

Introduction

Chronic exertional compartment syndrome (CECS) most commonly affects the young, military, and athletic populations and can be debilitating for active individuals. Typical symptoms include pain, paresthesias, muscle weakness, and discomfort described as squeezing or cramping that occur during exercise and intensify as exertion continues, but disappears when activity stops. Although the specific source of pain in CECS is not entirely understood, the condition is caused by a rise in intracompartmental pressure within an osteofascial space likely related to increased blood flow to muscles during exercise. CECS primarily affects the lower limb, but it can also occur in the thigh, hand, and forearm compartments. Originally thought to be a diagnosis of exclusion, CECS is now thought to be underdiagnosed, and thus increased understanding and awareness of this condition are critical. The symptoms can often be nonspecific, and the broad differential for lower leg pain can interfere with diagnostic clarity.

Owing to the difficulty and delay in diagnosis, the true epidemiology of lower leg CECS in the general population remains unclear. However, incidence rates among athletes and military members have been provided by individual studies, giving an idea of the prevalence of CECS within at-risk populations. In a large population of active military members, Waterman et al. reported an overall incidence rate of 0.49 cases per 1000 person-years. In a different cohort of recreational runners and military members, patients presenting with lower leg pain were evaluated and CECS was diagnosed in 27%–33% of all cases of lower leg pain. Davis et al. confirmed CECS diagnosis in 153 of 226 patients (67.7%; 250 of 393 legs) who presented with the appropriate symptoms and were suspected to have CECS. Among the group with confirmed CECS, 92.2% were active athletes. ^, Worth noting, and discussed by de Bruijn et al. who analyzed CECS in a large, mixed population, CECS is not completely limited to the athletic patient population and can also be found in less active individuals and diabetics.

Anatomy

Compartments are fascia-surrounded groupings of muscles, blood vessels, and nerves categorized by specific anatomic areas in the extremities. The fascia is relatively inelastic, keeping these structures in place and inhibiting stretching and expansion of the compartment space. The lower leg is divided into four compartments: anterior, lateral, superficial posterior, and deep posterior. The anterior compartment consists of the tibialis anterior, extensor hallucis longus, extensor digitorum longus, and peroneus tertius muscles, as well as the deep peroneal nerve and anterior tibial artery and vein. The main functions of the muscles in this compartment are dorsiflexion of the foot and ankle and extension of the toes, as well as inversion and weak eversion of the foot. The lateral compartment includes the peroneus longus and peroneus brevis muscles and the superficial peroneal nerve. These muscles primarily function in eversion of the foot and ankle and secondarily in plantar flexion of the ankle. The superficial posterior compartment comprises the gastrocnemius, soleus, and plantaris muscles and the sural nerve. Finally, the deep posterior compartment consists of the tibialis posterior, popliteus, flexor hallucis longus, and flexor digitorum longus muscles, as well as the posterior tibial artery, peroneal artery, and tibial nerve. The musculature of the combined posterior compartments function in plantar flexion and inversion of the foot.

Pathophysiology and Risk Factors

There are several proposed mechanisms leading to the development of CECS. The exact cause is not well understood. In normal functioning of the muscles of the lower leg, intracompartmental pressures increase and muscles enlarge with exertion and return to baseline within a few minutes of rest. Related to the pathophysiology of CECS is the capability of muscles to expand up to 20% in volume and weight during exercise, along with a rise in intracompartmental pressures against the surrounding inelastic fascia secondary to an increase in blood flow and edema. ^, Muscular hypertrophy that occurs over time in chronic exercise, particularly the involvement of repetitive activities, as well as fascial thickening, can lead to a reduction in the reserve volume available within the compartment. Moreover, compartment noncompliance found in individuals with CECS can cause an abnormal elevation in tissue pressure during normal muscle enlargement throughout exercise, leading to lower functioning and tolerance that typically returns to normal when activity stops and muscles return to resting size. ^, In some cases, although this is not necessarily a defining feature of CECS, patients can have elevated intracompartmental pressures that are sustained at rest. Long-standing, persistent abnormal pressures lead to the development of pain and may result in neurovascular compromise, paresthesias, and/or muscle weakness. ^, ^, An additional proposed contribution to the noncompliant compartments of the lower leg includes stiffer and thicker fascia, specifically reported of the anterior compartment, found in patients with CECS compared to unaffected patients. Furthermore, eccentric activities/moments may be a contributing factor, as patients with CECS have been shown to be more susceptible to pain with eccentric muscle contractions, which is indicated by studies reporting increases in compartment noncompliance as a result of eccentric exercise over time. ^, As summarized by Schubert, additional intrinsic and extrinsic factors may contribute to the development of CECS. Potential intrinsic factors include leg length discrepancy and malalignment, while extrinsic factors may consist of decreased strength, endurance, or flexibility; improper biomechanics; and insufficient training volume, intensity, or frequency. ^, Braver has also suggested genetic predisposition as a contributing factor in some individuals.

It was originally proposed that CECS-related pain may be the result of ischemia caused by microvascular compromise related to the elevated intramuscular and intracompartmental pressures that follow a significant volume increase in a relatively tight space. ^, ^, ^, However, this implication as a cause of pain is ambiguous and not universally accepted among researchers. It may be more likely that pain results from receptor stimulation through increased pressure. ^, A more widespread theory is related to abnormal muscle perfusion and alterations in gradients caused by pressure imbalances. ^, ^, Strenuous exercise can lead to microtrauma of muscular tissue and thus inflammation of the muscle and capillary bed. This can ultimately increase the pressure of the interstitial space through increased fluid flow from the capillaries into this space, subsequently producing the symptoms of CECS. This fluid shift can also be a result of impaired functioning of muscle tissue perfusion and deoxygenation that occurs as a result of intracompartmental pressure increase. As described by Brennan and Kane, when peripheral muscles are relaxed, they undergo perfusion and the arterial/venous gradient increases as a result. For the perfusion gradient to occur, it must be able to overcome normal resting intramuscular pressure and therefore be ≥30 mm Hg. In the case of CECS where pressures are greater than normal, this perfusion gradient is lost or reduced to the point of inadequacy for tissue viability. This results in reduced blood flow and subsequent pain that will only subside when these overriding pressures decline and the gradient returns to normal. ^, Previous studies have presented the results of imaging patients with CECS that demonstrate lack of perfusion in affected muscles after exercise, supporting this concept. Moreover, Fraipont and Adamson discussed the observation of greater deoxygenation of the muscle during exercise and delayed reoxygenation after exercise in patients with CECS compared to unaffected patients.

In 2013, Davis et al. performed a large-scale retrospective study over a 12-year period to examine the characteristics of patients who develop CECS. In the population studied, 60.1% (92 of 153) were females, with an overall average age of 24 years (range, 13–69 years) and an average body mass index of 25 (range, 18–38). A majority of patients (63.4%) presented with bilateral CECS, and the number of compartments affected within a single extremity ranged from one to all four compartments. The anterior compartment was most frequently affected, followed by the lateral compartment, deep posterior compartment, and finally the superficial posterior compartment. Of the 153 patients, 141 (92.2%) had symptoms present with activity only, while 12 patients reported symptom onset in daily activity alone. The patients who reported exercise-induced symptoms were predominantly competitive athletes (63.1%), whereas others participated only in recreational sports (36.9%). Among the competitive athletes, 64.1% (57 of 89) were involved in team sports, 28.1% (25 of 89) participated in individual sports, and 7 athletes reported activity in both. Among the competitive and team sports, patients who participated in soccer and competitive running (track or cross-country) had the highest proportion of affected athletes, followed by lacrosse and field hockey. Interestingly, each of these sports had noticeably more females diagnosed with CECS than males. In a review by Campano et al. a total of 1596 patients with diagnosed CECS were analyzed for demographics and characteristics across 24 publications. The authors found males to be predominately affected (70%). In addition, the authors found that 54% of the population consisted of military service members and that 29% were athletes (9% collegiate level and 8% professional level). This particular review reported bilateral CECS in 79% of patients, but reported the same findings of the most commonly affected compartments. Characteristic and risk factor studies have also been applied to the military population owing to the high incidence rates of CECS among active service members. Within this population, factors such as gender, age, race, military rank, and branch of service have all been associated with incidence rates. Understanding patterns in the characteristics of patients who develop CECS can provide useful insight on the diagnosis and treatment for both healthcare providers and patients. Likewise, determining specific risk factors can influence patient and provider decision-making and improve our understanding of the underlying causes leading to the development of CECS. Known risk factors include the use of creatine supplementation and anabolic steroids, which result in increased muscle volume and potential cause for abnormally high intracompartmental pressures. ^, ^, As previously mentioned, eccentric exercise and irregular biomechanics during running, such as rear-foot landing or overprotonation, can also increase the risk of experiencing CECS. ^, Finally, in addition to the aforementioned commonalities such as age and type of sport, the associated risk factors that have been suggested include overuse, history of trauma, and diabetes.

Signs and Symptoms

CECS is often misdiagnosed in the athletic population because it can present with a variety of symptoms. Generally, CECS causes exercise-induced pain in the lower leg that is localized to the affected compartment or compartments. ^, Typically, the pain is described as a dull, aching, cramping, or burning pain with a feeling of tightness or bursting in the lower leg. The pain begins within 15–20 min of the start of exercise and increases in intensity until the participant is forced to stop. There is typically no history of trauma or direct injury associated with the condition, and most often, there is a gradual onset of symptoms that arise after a long and intense period of exercise, unrelated to impact or weight-bearing. Occasionally, although transient, patients may experience accompanying motor weakness or neurologic symptoms, including numbness and tingling along the distribution of the nerve(s) within the affected compartment(s). Patients with CECS frequently report that the pain completely resolves shortly after discontinuing the aggravating activity. ^, ^, The condition often occurs bilaterally, with numerous studies reporting bilateral pain in 60%–90% of cases. ^, ^, In 2018, de Bruijn and colleagues analyzed the primary factors in predicting CECS of the lower leg. The authors found that within their large, heterogeneous population, gender, age, clinical history, bilateral symptoms, and painful or tensed compartment were associated with predicting CECS. According to the study, males and younger patients were more prone to develop CECS, in whom the median age at diagnosis was 25 years and the prevalence reduced as age increased. The researchers noted that their results confirmed previously reported findings.

Having a high level of suspicion based on patient history is critical for making a proper diagnosis, as physical examination of CECS can often be unremarkable because of the absence of symptoms when not engaging in exercise. ^, Therefore it has been recommended that if CECS is suspected, physical examination should be performed before exercise and immediately after exercise. ^, Findings after exercise often include pain on palpation of the affected muscles, pain during passive stretching of the muscle, and firmness of the compartments involved. Fascial defects may also be palpated in some instances. ^, Pronation and pes planus are often present in patients with CECS; therefore a gait analysis can be helpful as part of the overall evaluation. ^, Preexercise physical findings are usually normal; however, in severe and prolonged cases of CECS, atrophy of the affected compartment may be observed.

In the lower leg, any of the four compartments can be affected by CECS and differentiating symptoms may assist when determining which compartment or compartments are involved. The most commonly affected are the anterior and lateral compartments, followed by the deep and superficial posterior compartments. When the anterior compartment is affected, patients often complain of dorsal foot numbness and weakness with dorsiflexion of the toes and ankle. With involvement of the lateral compartment of the lower leg, patients experience dorsal foot numbness and eversion weakness. Involvement of the superficial posterior compartment results in lateral ankle or foot numbness, distal calf numbness, and posterior leg cramping. Patients with CECS of the deep posterior compartment develop weakness of plantar flexion, plantar foot numbness, and posterior leg cramping. ^, ^, ^, ^,

Differential Diagnoses and Diagnostic Testing

A variety of conditions are important to consider in both avoiding misdiagnosis and ensuring certainty in pursuing the official diagnosis of CECS, as diagnostic testing for this condition can be invasive. A summary of diagnoses to consider in patients presenting with symptoms similar to CECS is provided in Table 24.1 . ^, Common diagnostic tests that can assist in narrowing down the differential diagnosis include magnetic resonance imaging (MRI), electromyography, radiography, and bone scintigraphy.

Table 24.1

Differential Diagnoses to Consider When Evaluating Chronic Exertional Compartment Syndrome of the Lower Leg.

Stress fracture
Medial tibial stress syndrome (“shin splints”)
Tendon pathologies
Deep vein thrombosis
Fascial defects
Nerve entrapment syndromes
Popliteal artery entrapment syndrome
Claudication (peripheral artery disease)

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