Compartment syndrome is a serious condition that can be seen acutely following injury to the foot or leg, as well as chronically following exercise and exertion. In this condition, pressure abnormally builds within the 'compartments' of the legs or feet, which if untreated can lead to muscle death and foot deformity/dysfunction.

The compartments of the legs and feet are essentially the divisions of the body's tissue, where certain tissue such as muscles and blood vessels reside, much like rooms of a house. These compartments are separated by bands of unyielding tissue called fascia. There are several compartments in the lower legs and feet, and each contain various muscles, arteries, nerves, and veins. Compartment syndrome develops when the pressure inside one of these compartments becomes elevated. This pressure bears down on the muscles, eventually cutting off their microcirculation and leading to muscle cell death. This pressure can also harm nerve and larger blood vessel tissue. If the pressure is not released in time, the tissue damage could be permanent, leading to chronic pain, foot deformity, weakness, and poor sensation.

Compartment syndrome begins in one of two ways. The most common form of this condition develops when there has been a traumatic injury to the foot or leg. This trauma can take the form of a blunt or penetrating injury, as well as a crushing injury that causes multiple fractures or dislocated bones. The swelling and physical disruption in natural anatomy from these injuries increases the pressure in the compartments, which then collapses capillaries in the muscle tissue within. The next most common form develops in athletes or those with chronic exertional activities in which the muscles expand in size during the exercise or activity, leading to a temporary increase in the compartment pressure. The same tissue damage can occur during this scenario if the muscle is not allowed or unable to shrink back down to its usual size.

The symptoms of compartment syndrome can vary, but usually involve some combination of deep pain out of proportion from what is usual to a particular injury, pain from stretching, numbness, tense swelling, and muscle weakness (which may be hard to notice). After 2-4 hours of muscle circulation loss, permanent functional changes can develop in the muscles, which may include weakness. After 12 hours, toe and foot contractures can start to develop, leading to claw toes and drop foot (symptoms similar to the end result of a stroke). Nerve changes and sensation problems can develop in as little as 30 minutes, and if the pressure is persistent this can be permanent. These issues are present in all cases of compartment syndrome following trauma and constitute a medical emergency. Compartment syndrome following exercise may not necessarily have the same number of symptoms or severity, especially if the muscle is able to decrease its swelling. However, some cases are medical emergencies, especially if the swelling persists.

Compartment syndrome is diagnosed by directly measuring the pressure of the compartment or compartments. This is done using an instrument that has a probe that enters the tissue and measures the pressure. Normal pressure is less than 5mmHg, while in compartment syndrome it is higher. Cases in which the pressure is 30 mmHg or more after 8 hours need immediate intervention.

Treatment of traumatic and emergency exercise-related compartment syndrome is done in an operating room, with decompression of the compartment via a release of the constricting fascia tissue that surrounds it. Several compartments are released, even if only one is suspected of being the problem, as it may be hard to be absolutely certain. Any fracture present is also fixed, and the incisions are typically left open as to not create further tightness. These can be closed at a later time, or sometimes skin grafts are used to cover the exposed tissue. In the case of milder exercise-related compartment syndrome, non-surgical measures such as stretching, training modification, shoe inserts, anti-inflammatory medications, bracing, and physical therapy can be used to reduce the symptoms and improve the compartment space. Otherwise, surgery may be needed to physically increase the compartment space to allow the athlete to stay competitive.