A finger dislocation is a joint injury in which the finger bones move apart or sideways so the ends of the bones are no longer aligned normally. Finger dislocations usually happen when the finger is bent backward beyond its normal limit of motion.
The bones in the fingers are known by the medical terms phalanges and metacarpal bones. Every knuckle in the hands and fingers contains a joint between two of these bones, and any of these joints can be dislocated in an injury:
Distal interphalangeal joints are in the finger knuckles closest to the fingernails. Most dislocations in these joints are caused by trauma, and there is often an open wound in the location of the dislocation.
Proximal interphalangeal joints are the middle joints of the fingers. A dislocation in one of these joints is also known as a jammed finger or coach's finger. It is the most frequent hand injury in athletes, and it is especially common among those who play ball-handling sports, such as football, basketball and water polo. In most cases, the dislocation happens because the fingers are bent backward when an athlete tries to catch a ball or block a shot. Proximal interphalangeal joint dislocations also can happen when an athlete's fingers are twisted or bent by an opponent, especially when two athletes wrestle or grab for control of a ball.
Metacarpophalangeal joints are in the knuckles, located where the hand joins to the fingers. These joints connect the metacarpal bones in the palm with the first row of phalanges in the finger. Because these joints are very stable, metacarpophalangeal joint dislocations are less common than the other two types. When metacarpophalangeal dislocations do occur, they are usually dislocations of either the index finger or little finger (pinky).