The wrist is a complex joint structure on the human hand. Because of this complexity, the wrist exhibits a wide variety of functions.
What is the wrist?
The term wrist is a colloquial term, because according to the exact definition, the wrist consists of various partial joints. With the finger joints, the wrist represents the various joints of a human hand. Since the wrist has a large number of possible functions, it is characterized by a pronounced complexity. The wrist owes its functional diversity to the precise interaction of the individual partial joints. In the history of development, only humans have fully developed the ability to rotate the forearm. This skill is an important prerequisite for the use of the hand as a gripping tool. Because of its bony and structural diversity, the wrist is highly susceptible to injury, especially in falls that affect the hand. In addition, the wrist is at increased risk of overuse because of its multiple stresses.
Anatomy and structure
From an anatomical point of view, the wrist consists of various subunits. A first thumb-side subunit is formed by the so-called radius, a bone of the forearm. The wrist unit of the radius is complemented by a series of carpal bones called the lunate, scaphoid, and triangular bones. A second unit of the wrist is located between the aforementioned first row carpal bones and additional carpal bones (main bone, hook bone, and large and small polygonal bones), which are dubbed second row bones. In addition, the ulna bone of the forearm in conjunction with its stylar process is considered a functionally important part of the wrist on the small finger side. Finally, the wrist receives its stability from surrounding tendons and ligaments. The musculature associated with corresponding tendons is found only on the forearm.
Function and tasks
The various partial joints that make up the wrist, when working together, allow the joint to perform a variety of functions and tasks. For example, the cooperation of the partial joints allows the wrist to flex in the direction of the palm (also known in medicine as palmar flexion). Such flexion is possible in a healthy person up to an angle of about 80 °. In addition, the wrist can be extended in the opposite direction (the direction of the back of the hand) with the help of the partial joints. A corresponding extension is also known as dorsal extension. Finally, the wrist can also be spread laterally in the direction of the thumb or little finger. If the wrist is functional, this spreading can reach radii of approx. 30 – 40 °. With its many functions, the wrist assumes, among other things, the tasks of bringing the hand into a desired position and holding it there with sufficient stability. For example, the functions of the wrist form the basis of hand and finger movements such as gripping and firm grasping, as well as stable precision grip.
Diseases and complaints
Possible wrist complaints can be caused by both diseases and injuries. Among the most common diseases that occur at the wrist is, for example, the so-called carpal tunnel syndrome, which is characterized by nerve compression at the level of the carpus. Carpal tunnel syndrome at the wrist usually initially manifests itself in pain that radiates into the arm – in the further course, muscle atrophy can occur at the ball of the thumb. Possible causes behind this syndrome at the wrist are, for example, overstraining or bone fractures near the wrist. Tendonitis can also affect the wrist – in this case, the inflammation usually manifests itself as stabbing pain. If a so-called ganglion is present in the wrist, this is a benign tumor formation on the joint capsule. Frequently, the causes of a corresponding ganglion at the wrist cannot be clearly diagnosed. Other diseases that can affect the wrist include osteoarthritis (also known colloquially as joint wear).Finally, common injuries that can occur to the wrist due to external force include fractures (broken bones) of the radius near the joint and torn ligaments – fractures can basically affect any bone in the wrist.
