Understanding the basic anatomy of the hand and fingers is useful in understanding different types of finger injuries, broken fingers, and how some treatments differ from others.
The hand is divided into three sections: 1) wrist, 2) palm, and 3) fingers.
- The wrist has eight bones, which move together to allow the vast ranges of motion of the wrist.
- The palm or mid-hand is comprised of the metacarpal bones. The metacarpal bones have muscular attachments and bridge the wrist to the individual fingers. These bones frequently are injured with direct trauma such as a crush injury, or most commonly, a punching injury.
- The fingers are the most frequently injured part of the hand. Fingers are constructed of ligaments (strong supportive tissue connecting bone to bone), tendons (attachment tissue from muscle to bone), and three phalanxes (bones). There are no muscles in the fingers; and fingers move by the pull of forearm muscles on the tendons.
- The three bones in each finger are named according to their relationship to the palm of the hand. The first bone, closest to the palm, is the proximal phalanx; the second bone is the middle phalanx; and the smallest and farthest from the hand is the distal phalanx. The thumb does not have a middle phalanx.
- The knuckles are joints formed by the bones of the fingers and are commonly injured or dislocated with trauma to the hand.
- The first and largest knuckle is the junction between the hand and the fingers – the metacarpophalangeal joint (MCP). This joint commonly is injured in closed-fist activities and is commonly known as a boxer’s fracture.
- The next knuckle out toward the fingernail is the proximal interphalangeal joint (PIP). This joint may be dislocated in sporting events when a ball or object directly strikes the finger.
- The farthest joint of the finger is the distal interphalangeal joint (DIP). Injuries to this joint usually involve a fracture or torn tendon (avulsion) injury.
Bones of the Hand