The lunate bone is a bone found in each hand just above the wrist joint. It is a type of carpal bone at the base of the hand. More specifically, it is located on the outside of each hand below the pinky and opposite the base of the thumb. It sits next to the scaphoid bone and adjacent to the triquetral, capitate and hamate bones. It is the easiest carpal bone to dislocate. Its function is similar to that of other carpal bones in the hand.
Carpal bones such as the lunate bone can be found in all quadrupeds. The carpal bones allow the wrist to move smoothly and to reach the angles that it does. These bones do not form part of the fingers, but they are equivalent to the tarsus bone cluster found in the foot, which allows ankle movement.
These movements are aided by four sets of ligaments. One set links the carpal bones to the radius bone in the arm. One set links the carpal bones to one another. Two sets link the carpal bones to the metacarpal bones that form the bases of the fingers and thumb.
The lunate bone is crescent-shaped, hence its name. It has six surfaces and ligaments attaching it to each of the corresponding bones around it. The dorsal and palmer surfaces are for attaching ligaments. The lateral, medial and inferior surfaces interact with the other carpal bones — the lateral with the scaphoid, the medial with the triquetral and the inferior with the capitate and hamate bones. The medial surface articulates with the triquetral bone and the superior with the radius.
Dislocation easily happens to the lunate bone. The dislocation is often caused by falling and is just a part of a more serious injury. Athletes such as tennis players, baseball players and basketball players may also dislocate their lunate bones during play. Common symptoms of lunate bone dislocation include swelling, pain and a loss of movement of the wrist. The bone needs to be put back in its place; this is usually done through minor surgery.
Kienbock’s disease is one disease that primarily affects the lunate bone. The main symptom of the disease is a pain in the wrist and bones around the area of the lunate. Over time, this develops into swelling and a loss of movement. The pain and other symptoms are caused by degeneration of the bone. The overall cause of this is unknown, but is thought to be related either to a loss of blood supply to the bone or dislocation.
If caught early, the disease can be treated without threatening the bone. This can be done by putting the bone in its correct place and ensuring there is a good supply of blood to it. If the bone has begun to degenerate, it may need replacing or fusing.