The wrist is a complex and highly mobile joint that allows for a wide range of hand movements, making it indispensable for daily activities. Its intricate structure facilitates actions such as grasping, rotating, and fine manipulation. Understanding the bones that form this joint provides insight into its remarkable capabilities.
The Carpal Bones
The true “wrist bones” are a group of eight small, irregularly shaped bones called the carpal bones. These bones are organized into two distinct rows, forming a compact unit within the wrist joint.
The proximal row consists of four bones, moving from the thumb side to the pinky side: the scaphoid, lunate, triquetrum, and pisiform. The scaphoid is the largest bone in this row, while the pisiform is a small, pea-shaped bone embedded within a tendon. The distal row also contains four bones, progressing from thumb to pinky side: the trapezium, trapezoid, capitate, and hamate. The capitate is the largest of all the carpal bones.
Bones Connecting to the Wrist
The carpal bones are positioned to bridge the gap between the forearm and the hand. They articulate with the two long bones of the forearm, the radius and the ulna, at their distal ends. The proximal row of carpal bones, particularly the scaphoid and lunate, connects directly with the radius, forming the primary wrist joint, known as the radiocarpal joint.
The distal row of carpal bones articulates with the bases of the five metacarpal bones, which are the long bones that form the palm of the hand. These connections create the carpometacarpal joints, linking the hand to the forearm. This anatomical arrangement allows for the hand’s diverse range of motion relative to the forearm.
Locating Your Wrist Bones
To feel the general area of your wrist bones, begin by identifying the two prominent bony bumps on either side of your wrist, just above the hand. On the thumb side, you can feel the styloid process of the radius, which is part of your forearm bone. On the pinky side, you will find the styloid process of the ulna, another part of your forearm.
The carpal bones themselves are located in the region between these forearm prominences and the base of your hand. A small, round bone called the pisiform is often easily felt on the pinky side of your palm, at the base of the wrist, by pressing firmly below the wrist crease. Another palpable landmark is the scaphoid bone, which can sometimes be felt in the “anatomical snuffbox,” a small indentation on the back of your hand at the base of the thumb when your thumb is extended.