The wrist is a complex joint that joins the arm to the hand. A number of different bones enable the movement and strength that we need to use our hands. The anatomy of the wrist includes bones, ligaments and tendons, muscles, blood vessels and nerves.
The wrist is a condyloid synovial joint. The types of movement includes flexion (up), extension (down), abduction (little finger side of hand moving away from body), adduction (thumb side of hand moving towards body). There is more limited movement for abduction due to a longer (or more distal) styloid process. Circumduction enables the combination of all the movements.
The carpal bones join the radius and the ulna of the forearm to the bones of the hand or metacarpal bones. There are eight small carpal bones which are in two rows across the wrist. The proximal row is closest to the radius and ulna. The upper end of the wrist includes the scaphoid, lunate, pisiform and triquetral. These connect with the forearm bones. The second or distal row includes the hamate, capitate, trapezoid and trapezium. Each small carpal bone forms a joint with the bone next door, so the wrist is made up of a number of smaller joints.
The proximal articular surfaces of carpal bones (where bones meet) are covered with articular cartilage. It is white, shiny and rubbery, designed to enable the joint surfaces to move against one another without causing damage. It is thinner in the wrist joint which does not have to bear a lot of weight. It enables joints to move easily without causing damage and helps to absorb shock.
The wrist ligaments are named according to where they are positioned in the joint and the bones they connect. Radiocarpal and ulnocarpal ligaments connect the radius and ulna. Palmar ligaments are positioned on the inside of the hand across the palm while a dorsal ligament supports the back of the hand.
Ligaments connect the bones, forming a joint capsule around the meeting place of two bones. This is a watertight sac, surrounding the join, which contains synovial fluid, a lubricating liquid. The carpal bones are surrounded by a joint capsule which support them.
The two collateral ligaments support each side of the wrist, connecting the forearm. The ulnar collateral ligament connects to the ulnar, starting at the ulnar styloid, which is a small bump on the edge of the wrist near the wrist joint. It then connects to the pisiform, the triquetrum and to the transverse carpal ligament which is situated across the front of the wrist. The ulna collateral ligament helps to support the small disc of cartilage where the wrist meets the ulna and is known as the triangular fibrocartilage complex. This offers a range of motion and cushions the wrist joint. The ligament helps to stabilise the disc of cartilage and works to stop the wrist bending too far towards the thumb.
The ligament on the thumb side of the wrist is the radial collateral ligament which connects the radius to the rest of the wrist joint. It begins at the radial styloid, a small bump on the outer edge of the radius and is connected to the scaphoid carpal bone below the thumb. This ligament stops the wrist from bending too much to the side away from the thumb.
Other important ligaments of the wrist include the palmar radiocarpal ligament which supports the palm side of the wrist, attaching the radius to the capitate bone. It is in two parts, including the radiocapitate part of the radiocarpal ligament which connects to the capitate bone and the radioscapholunate part of the palmar radoiocarpal ligament which connects the radius to the scaphoid and lunate bones.
The palmar ulnocarpal attaches the ulna to the lunate bone (ulnolunate part of the palmar ulnocarpal ligament) and the triquetral bone (ulnotriquestral part of the palmar ulnocarpal ligament).
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Educational poster of the anatomy of the hand and wrist
Wire-mounted, flexible skeleton model of shoulder, arm and hand. Available as right or left arm.
Unmounted set of bones cast from the hand of an adult male. Ideal for anatomy students.
Poster shows the anatomy of both normal functioning and common injuries found in the hand and wrist.