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Anatomy of the Hand & Wrist
Understanding how the hand and wrists work
The Complex Anatomy of the Hand & Wrist
Wrist Anatomy
Wrist bones are called carpal bones. The wrist joint is the complex joint between the distal ends (furthest from the body) of the radius and ulna (two forearm bones) and the metacarpal (hand) bones. It connects the forearm to the hand and allows a good range of motion. Repetitive use, however, frequently leads to injuries.
Bones and Articulation
The ulna is the larger of the two forearm bones, although it tapers at the wrist end to become narrower than the radius at this point. The radius is positioned on the thumb side of the wrist, and the ulna on the little finger side. They form the wrist joint with the carpal bones. There are eight carpal bones arranged in two rows, proximal and distal:
- Capitate
- Hamate
- Lunate
- Pisiform
- Scaphoid
- Trapezium
- Trapezoid
- Triquetrum
The scaphoid bone is the largest carpal bone and crosses both rows. The scaphoid and the lunate are the two bones that join the radius and ulna to form the wrist joint.
Hand Anatomy
The human hand consists of a broad palm (metacarpus) with five digits, attached to the forearm by a joint called the wrist (carpus).
Fingers
We use the four fingers on our hands to perform the outermost tasks. These four digits can be folded over the palm, allowing us to grasp objects. Each finger has an informal name, which is easy to remember, to distinguish it from the others. Starting closest to the thumb:
- Index finger, pointer finger or forefinger
- Middle finger
- Ring finger
- Little finger or 'pinky'
Bones
The human hand has 27 bones. The carpals, or wrist, accounts for eight of them. The metacarpals, or palm, contain five. The remaining 14 are bones in the fingers and thumb.
The palm has five bones known as metacarpal bones, one to each of the five digits. These metacarpals have a head, a shaft and a base.
Human hands contain 14 digital bones, also called phalanges, or phalanx bones: two in the thumb (the thumb has no middle phalanx) and three in each of the four fingers. These are the distal phalanx (carrying the nail), the middle phalanx and the proximal phalanx.
Sesamoid bones are small, ossified nodes embedded in the tendons. They provide extra leverage and reduce pressure on the underlying tissue. Many exist around the palm at the bases of the digits. The exact number varies among different people.
Articulation
The articulation of the hand is more complex and delicate in humans than in any other animal. Without this extra articulation, we wouldn’t be able to operate a wide variety of tools and devices or achieve the range of possible hand gestures.
These are the complex articulations:
- Interphalangeal articulations of the hand (the hinge joints between the finger bones)
- Metacarpophalangeal joints (where the fingers meet the palm)
- Intercarpal articulations (where the palm meets the wrist)
- Wrist (sometimes viewed as belonging to the forearm)
Most Common Hand and Wrist Injuries
While hand and wrist injuries are common, some people never seek treatment. Unfortunately, delaying the diagnosis and treatment may result in long-term problems or even a permanent disability.
At Beth Israel Deaconess Hospital–Needham, our specialists are highly trained to diagnose and treat your hand or wrist issue before long-term issues develop.
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Services & Specialties
Our hand and wrist providers work with these and other specialties to get you the care you need.
