The anatomy of the wrist includes all of the structures that make up the wrist joint itself. These are the bones, ligaments, joint capsule, and cartilage, and the muscles and other tissues around the joint. Known as the radiocarpal joint, the articulation at the wrist is found where the radius bone in the forearm meets the carpus, which is a cluster of small bones in the base of the hand. Crossing the radiocarpal joint are the ligaments connecting these bones, as well as the tendons of the muscles that move the joint and other soft tissues like nerves and blood vessels. Also often included in a discussion of the anatomy of the wrist is the distal radioulnar joint, the articulation between the radius and ulna bones in the forearm that is found immediately above the radiocarpal joint.
As the main articulation where the arm meets the hand, the radiocarpal joint is synonymous with the wrist. It is found where the far end of the radius, one of two long bones in the forearm, meets the near end of carpal bones in the hand. Clustered like small rocks in the base of the hand, the carpus consists of eight irregularly shaped bones. The bones in the proximal row that articulate with the distal radius are called the scaphoid, lunate, and triquetral bones.
Between the carpals and the radius is another key component of the anatomy of the wrist, the articular disk. As the radiocarpal joint is a condyloid joint, it features an oval-shaped disk that fills the joint capsule between the bones to cushion them against one another during the many movements the wrist can perform, including flexion and extension, adduction and abduction, or bending the hand toward the pinky or thumb side, and circumduction, or circling the wrist.
The anatomy of the wrist also includes several major ligaments, the bands of fibrous tissue holding together the bones of the hand, wrist, and forearm. Five ligaments hold the eight carpal bones together just beyond the radiocarpal joint. These are the radiate carpal ligament, the pisohamate ligament, and the dorsal, palmar, and interosseous intercarpal ligaments. The carpus is connected to the radius along the thumb side of the wrist by the radial collateral ligament and on the front and back side of the wrist by the palmar and dorsal radiocarpal ligaments, respectively. Likewise, the carpus is linked to the ulna bone in the forearm, which runs parallel to the radius but is not a part of wrist joint, by the ulnar collateral ligament on the pinky side of the wrist as well as the palmar ulnocarpal ligament on the palm side of the wrist. The ulna and radius are linked to each other at a pivot joint just above the wrist called the distal radioulnar joint by the volar, or palmar, and dorsal radioulnar ligaments.
In addition to several nerves and blood vessels crossing the wrist joint, the anatomy of the wrist is made complete by the tendons of the muscles of the forearm as they enter the hand. On the anterior or palmar surface of the wrist are the tendons of the muscles that flex, abduct, and adduct the wrist, among them the flexor carpi radialis and ulnaris muscles and flexor digitorum muscles. Muscle tendons crossing the dorsal surface of the wrist are those belonging to the muscles of the posterior forearm, muscles that extend the wrist like the extensor carpi radialis and ulnaris and the extensor digitorum.
