Knees after corrective surgery. X-ray of a section through the knees of a 75-year-old patient following valgisation osteotomy of the left knee (right) to correct joint displacement, and a previous total knee replacement of the right knee (left). Here, the prosthetic knee joint (white, lower left) and osteotomy support (white, lower right) can be seen. Osteotomy is a procedure whereby a bone is shortened or lengthened to alter its alignment.