The wrist is made up of eight small bones, called carpal bones, which are held together by ligaments. The carpal bones connect the bones in your forearm to the bones in your hand. The median nerve, which provides motion and feeling to the wrist, thumb, and fingers, passes from the forearm to the hand through a confined space in the wrist called the carpal tunnel. It is much like a tunnel you drive your car through, having a ceiling, floor, walls, an entrance, and exit. The carpal ligament is the tough ceiling of the carpal tunnel.

Several tendons also pass through this tunnel. Each one has a special slippery covering called the synovium, that allows the tendons to glide smoothly as you move your fingers. In a normal wrist, there is adequate room for both the tendons and the nerve.