Exertional compartment syndrome (ECS) is a condition that causes pain with exertion. Although the condition can occur in other compartments, 95% of cases are in the lower leg. The median age of onset is 20 years; males and females are equally affected. The condition is most common in runners, but it also occurs in other running sports including soccer, field hockey, basketball, and lacrosse. In 82% of cases, the pain is in both legs.

There are four compartments in the lower leg — one in the front, one on the outside, and two in the back (superficial and deep). Each compartment has a covering of fascia. Exertional compartment syndrome occurs when the muscles expand during exercise and the fascial covering around the muscles becomes too tight. Patients then experience an aching pain in the compartment that becomes sharp if they continue activity. You may develop muscle weakness and sensory disturbance in the involved compartment. The symptoms are typically relieved quickly when you stop the activity.

The evaluation for compartment syndrome includes evaluating for other causes of leg pain such as medical tibial stress syndrome (shin splints), a stress fracture, a nerve entrapment or popliteal artery entrapment syndrome. MRI and other imaging studies have been used to diagnose compartment syndrome, but the standard diagnostic test is a measurement of the compartment pressures. These pressures are measured by using a special instrument that analyzes pressure through a needle placed in the muscle. Pressures are measured at rest and then one minute and five minutes after exercise. With compartment syndrome, the pressures are elevated, especially after exercise.