The most common reason for an osteotomy is arthritis of the knee that is limited to a single area or compartment. This usually occurs because of a severe bow-legged or knock-kneed shape to the knees. Because the other parts of the knee remain healthy, an osteotomy can be used to direct most of the body weight through this area, avoiding the pressure across the arthritic part of the knee and the resultant pain. Other reasons osteotomies can be used include cartilage restoration procedures and realignment after a malunion (abnormal healing position) of a fracture.