The procedure of osteotomy means that a wedge is taken from (or inserted into) the femur (thigh bone) or tibia (shinbone) to realign the bones and normalise the forces through them.
It is possible to tackle the effects of the arthritis rather than the arthritis itself by realigning the bow legs or knock knees which may result from destruction on one side of the joint, thus redistributing the forces through the arthritic area.
There are 3 essentially different types of osteotomy -
A derotational osteotomy is where the bone is cut and the two bits rotated and re-fixed in a different alignment. An example might be a derotation osteotomy for femoral or tibial rotation abnormalities, eg femoral anteversion
A displacement osteotomy involves cutting through a part of the bone and sliding it to the side, eg T.T.T. (tibial tuberosity transfer)