Kienbock's disease is a condition of avascular necosis (failure of the blood supply) of the lunate. This is a small bone in the middle of the wrist. The cause of Kienbock's is not known though there are many theories and associations that have been described.
Kienbock's normally presents with a gradual onset of pain and increasing stiffness in the wrist, it is most typically described in young males in the dominant wrist but can affect both men and women and may present at any age. Some times the first presentation of Kienbock's is following an injury when an x-ray is taken and patients may be refered with a "lunate fracture".