Osteoarthritis. Coloured x-ray of the knees of a 73-year-old patient following a valgisation osteotomy procedure to the left knee (right) to correct a lateral joint displacement caused by osteoarthritis (OA). Osteoarthritis is a disease resulting from the breakdown of joint cartilage (connective tissue) and the underlying bone. It often affects the large weight-bearing joints, such as the hips and knees, and causes joint pain and stiffness. An osteotomy is a type of surgery which provides pain relief for osteoarthritis patients, and involves a bone being shortened or lengthened to alter its alignment. It is conducted approximately 10 years before a total knee prosthesis procedure is required. Here, the metallic osteotomy fixation staple (white, right) can be seen at the top of the left tibia (shin bone).