In many parts of the body, muscles (along with the nerves and blood vessels that run alongside and through them) are enclosed in a "compartment" formed of a tough membrane called fascia. When muscles become swollen, they can fill the compartment to capacity, causing interference with nerves and blood vessels as well as damage to the muscles themselves. The resulting painful condition is referred to as compartment syndrome.

Compartment syndrome may be caused by a one-time traumatic injury (acute compartment syndrome), such as a fractured bone or a hard blow to the thigh, by repeated hard blows (depending upon the sport), or by ongoing overuse (chronic exertional compartment syndrome), which may occur, for example, in long-distance running.