Carpal bones
Eight small bones arranged in two rows form the wrist's core, allowing a combination of gliding and rotating movements between the forearm and hand.
The wrist is formed by eight small carpal bones arranged in two rows, connecting the forearm bones to the hand's metacarpals. This arrangement allows a wide range of wrist motion while transmitting forces generated by the powerful forearm muscles to the fingers.
Long tendons originating in the forearm cross the wrist through fibrous tunnels to reach the fingers, and several major nerves, including the median nerve, pass through similarly narrow spaces, which is why compression syndromes are common in this region.
Key structures
Carpal tunnel
This narrow tunnel on the palm side of the wrist, bounded by carpal bones and a tough ligament, is a common site of nerve compression when tissue swelling or thickening reduces the available space.
Flexor digitorum tendons
These long tendons run from the forearm through the wrist and palm to bend the fingers, and are commonly involved in overuse conditions such as trigger finger.
Extensor tendons
Tendons running across the back of the wrist and hand straighten the fingers and wrist, and can become irritated with repetitive use, as seen in De Quervain's tenosynovitis at the thumb side.
Median nerve
This nerve travels through the carpal tunnel to supply sensation to the thumb, index, and middle fingers and motor control to some thumb muscles, making it the nerve most often affected by wrist compression.
Ulnar nerve (wrist portion)
Passing through a separate tunnel at the wrist, the ulnar nerve supplies the ring and little fingers and many of the small muscles that control fine finger movements.
Planes & range
Combined wrist flexion (about 80°) and extension (about 70°) allow the hand to be positioned across a wide range for gripping and fine motor tasks, complemented by radial and ulnar deviation of roughly 20–35°.
This dense packing of bone, tendon, and nerve in a small space explains why wrist and hand conditions often involve a specific tunnel or tendon compartment rather than the joint as a whole.
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