Kienbock’s disease, or avascular necrosis of the lunate, is a condition in which the lunate bone, one of eight small carpal bones in the wrist, loses its blood supply, leading to death of the bone. The lunate is a central bone in the wrist, important for proper movement and support of the joint. The lunate, along with the adjacent bones on either side of it, the scaphoid and triquetrum, make up the proximal carpal row. This row of bones articulates with the 2 forearm bones (the radius and ulna), to form the portion of the wrist that provides the most motion (Figure 1). Damage to the lunate can lead to pain, stiffness, and in late stages, arthritis of the wrist. Kienbock’s disease is most common in men between the ages of 20 and 40 and rarely affects both wrists.