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Chronic exertional compartment syndrome (CECS) of the lower leg, defined as a condition with exercise-induced pain due to increased intramuscular pressure (IMP), has previously mainly been described in running athletes, and etiologic factors are poorly described. CECS has not been reported to occur together with other diseases and information about consequences on muscles morphology after treatment with fasciotomy is largely unknown. We investigated etiologic and pathophysiologic aspects to CECS in a consecutive series of 63 patients with exercise-related leg pain and in 17 diabetic patients with symptoms of intermittent claudication but no circulatory insufficiency. Clinical examination, radiography, scintigraphy and IMP measurements at rest and after reproduction of symptoms were done. Patients with CECS were recommended treatment with fasciotomy. Biopsies were taken from the tibialis anterior muscle at time of fasciotomy and at follow-up 1 year later. For comparison muscle samples were taken from normal controls. Enzyme- and immunohistochemical and morphometric methods were used for analysis of muscle fiber morphology/pathology, fiber phenotype composition, mitochondrial oxidative capacity and capillary supply.

Thirty-six of the 63 patients fulfilled the criteria for diagnosis of CECS in the anterior tibial compartment. The CECS patients could be divided into different etiologic groups: 18 healthy, 10 with history of trauma against the lower leg, 4 diabetic patients and 4 others. Only 5 of 36 CECS patients were athletes. The results after fasciotomy were good or excellent in 41 of 57 treated legs.  Sixteen of the 17 diabetic patients were diagnosed with CECS, 11 with diabetes type 1 and 5 with type 2. The diabetic patients differed from the other groups with longer symptom-duration, shorter pain-free walking distance, firm and tender lower leg muscles and higher IMP. The postoperative outcome was good or excellent in 15 of 18 treated legs. The muscle biopsies taken at fasciotomy showed frequent histopathological changes including small and large sized fibers, fiber atrophy, internal myonuclei, split fibers, fibrosis, disorganization of mitochondria in contrast to healthy CECS subjects having low muscle capillarization as the main finding. Muscular abnormalities were generally more complex, severe and widespread in diabetic patients. After 1 year, the majority of CECS patients could return to unrestricted physical activity and the histopathological muscle changes were clearly reduced. The muscle fiber size was larger and the muscles contained signs of regeneration and repair. Remaining muscle abnormalities were present mainly in diabetic patients.

CECS is a new differential-diagnosis in diabetic patients with symptoms of claudication without signs of vascular disease. A low ability for physical activity, reflected by the signs of both myopathy and neuropathy, indicates that high IMP and circulatory impairment has deleterious effects for the involved muscles. Increased physical activity and normalization of muscle morphology 1 year after treatment shows the benefit of fasciotomy. The more severe clinical and morphological findings in diabetic compared to healthy subjects with CECS indicate differences in the pathogenesis. The unrestricted physical ability after treatment is very important for diabetic patients, since physical activity is an essential part of the therapy of the disease.