Collaboratively, the wrist and hand form the single most complex and one of the most commonly used systems in the human body, containing 29 bones, each connected by a ligament, 27 joint articulations, and more than 30 muscles. As a result of the tremendous number of components contributing to their functionality, the hand and wrist can be easily injured.
Connecting the hand to the forearm, the wrist is comprised of 8 carpal bones, the bases of 5 metacarpal bones in the hand, and the ends of the radius and ulnar bones of the forearm. Of the 8 carpal bones, 4 are proximal, meaning they are nearest to the anatomical center of the body, and 4 are distal.
There are 5 metacarpal bones in the hand and wrist, which extend to the base of the finger bones, which are known as phalanges. Each finger has 3 phalanges, while the thumb has two.
The joint connecting the wrist to the hand, or the distal ends of the radius and ulna with the carpal bones, has multiple articulations, which allows for a considerable range of motion. Collectively called a condyloid joint, the many connection points of the wrist allow for the movements of flexion and extension, supination and pronation, as well as ulnar deviation and radial deviation, which is the hand-waving motion of lateral flexion.
The normal range of motion of wrist movements:
|Ulnar Deviation||30 degrees|
|Radial Deviation||20 degrees|
In addition to the articulations allowing movement of the wrist, there are many joints in the hand allowing for freedom of motion in the fingers, which are the metacarpophalangeal joints at the base, and the interphalangeal joints, which allow precise bending of the fingers.
Muscles empower the movements of the wrist and hand digits. They can be categorized based on the type of movement they facilitate:
In addition to the many bones, joints, and muscles composing the complex anatomy of the wrist and hand, there are a number of ligaments and tendons that act as connectors, acting as essential components to a fascinating system.