As you have discovered, compartment syndrome is an acute medical problem. Pressure within the compartments of the forearm builds up and cuts off the blood supply to the muscles. The increased pressure occurs as a result of inflammation after an injury, surgery, or in most cases, repetitive overuse of the muscles.
This condition is seen most often in the lower leg, but can affect the arm as well. Most patients with compartment syndrome have been engaged in activities requiring significant demand on the muscles of the forearm. Forearm chronic exertional compartment syndrome has been reported in manual laborers, rock climbers, tennis players, kayakers, and weight lifters.
There are six known compartments in the forearm. Three on the extensor (back) side and three on the volar (flexor or under) side. In the forearm, the volar compartment is affected more often than the extensor compartment.
Fascia (sheaths of connective tissue) separate the compartments. It’s these bands of fibrous tissue that constrict the space. Inflammation in the confined space (fascial compartment) takes up any extra space. Muscles cannot contract and expand. Increasing pressure keeps the cycle of pressure – restriction – blood loss – inflammation – pressure going.
Without prompt treatment, nerve damage and muscle death can occur. Although rest and activity modification may be prescribed for mild cases early on, chronic exertional compartment syndrome usually requires surgery.
Sometimes during the operation, the surgeon can see evidence of a previous injury that may have led to the compartment syndrome. Long-term muscle exertion and chronic overuse combined with the results of a prior injury can eventually create the environment described that leads to compartment syndrome. Although it seems like it came on suddenly, usually, there has been a long period of development.