The osteotomy takes a patient who is knock-knee'd or bow-legged and straightens him or her out. Indeed, these limb deformities can be both the consequence and the cause of arthritis. Specifically, patients who are knock-knee'd or bow-legged place excessive pressures on one side or the other of their knee.

The osteotomy transfers the pressure from the unhealthy (diseased) side and shifts it to the healthy side. The operation is not performed in the knee itself, but rather just below, or more rarely just above the knee joint. When the operation is below the knee, the procedure is carried in the "tibia" bone, and when carried out above, it is within the "femur" bone.

An osteotomy, therefore, does not treat the worn out, arthritic area itself. When successful, it does two things:

- It alleviates pain by shifting pressure away from the painful area.
- It halts the progression of arthritis, again, by shifting pressure off the
diseased area.

The indications for an osteotomy depend on the following factors:
- The intensity of the pain and the severity of the deformity.
- Age. Younger patients are better candidates than older patients.
- Radiographic findings. Certain x-ray findings have been associated with
a successful outcome.