The etiology of avascular necrosis of the lunate (Kienbock's disease) is not clear. It is thought to be due to single or repetitive trauma to the lunate which impairs its blood supply. Note on the PA and oblique radiographs that the lunate bone appears more opaque than the surrounding carpal bones.

These injuries should be immobilized with a thumb spica cast and referred to an orthopedic surgeon or hand specialist for follow-up.