The wrist joint is an intricate joint between the carpal bones and the far, or distal, ends of two forearm bones. The wrist is a complex hinge joint that allows for a good range of motion by moving up and down and side to side. Because of the wide range of motion and complexity of design, wrist joints are exceptionally prone to injury due to overuse and repetitive tasks.
The wrist joint is made up of many bones, as well as ligaments, tendons, muscles, and nerves. The wrist begins at the distal portion of the large, tapering ulna, the forearm bone on the side of the little finger, and the radius, the forearm bone nearer the thumb. Eight carpal bones form in two rows that help make up the joint. The scaphoid, which is the largest of the carpal bones, crosses over both rows, and, along with the lunate bone, articulates with the ulna and radius.
Although there are many bones in the wrist joint, ligaments and tendons are also important to its structure. All eight carpal bones are surrounded by the soft, flexible fibers of ligaments that serve not only to protect and lubricate the bones, but to connect them with each other. Tendons are tough, fibrous tissues that connect the bones with muscle tissue, and aid in connecting the forearm with the hands and manipulating the fingers.
The wrist joint is also made up of many muscles, the majority of which are within the forearm. Most of these muscles help with the movement of the wrist, thumb, and fingers. In addition to moving forward and backward, some of these muscles also help the wrist move from side to side.
While bones, ligaments, tendons, and muscles all aid in the support and movement of the joint, nerves help to provide sensation in the hand and fingers. Three nerves begin in the forearm, cross the wrist, and land in the hand. The ulnar nerve supplies feeling to the small finger and the external portion of the ring finger, and the radial nerve provides the thumb with sensation. The median nerve is split into branches that supply feeling to the index and middle finger, and the internal portion of the ring finger.
Because of the amount of usage and the complexity of the joint, the wrist is prone to many aches and pains. One of the most common complaints is carpal tunnel syndrome. This is generally caused when the median nerve becomes compressed, thus causing pain or numbness in the thumb, middle, and index fingers. Other common injuries may be due to breaks, strains to the ligaments, tendinitis, and arthritis.