Q: What can you tell me about having an osteotomy for half-knee arthritis? Will it do any good? Can I really get some new cartilage to grow on the damaged half with this operation?

A: Knee arthritis affecting only one side of the joint is a common problem. It occurs as a result of uneven load and weight-bearing on the joint. This type of unicompartmental arthritis is the result of malalignment somewhere in the leg.

Treatment choices depend on the age of the patient, activity level, intensity of the painful symptoms, and severity of the joint damage. One possibility is a procedure called an osteotomy.

The surgeon cuts through the proximal tibia (upper part of the lower leg bone) and makes a wedge- or pie-shaped opening. Bone graft material is used to hold the wedge open until the patient's own bone fills in the gap. A metal plate holds the two edges of the bone in place until complete fusion takes place.

An osteotomy of this type realigns the angle made between the bones of the leg. It can shift your body weight so that the healthy side of the knee joint takes more of the stress. This procedure evens out the weight from one side of the joint to the other side and takes some of the load and pressure off the damaged side.

But how well does it work for unicompartmental osteoarthritis? The idea of reducing load on the injured side in order to preserve the tissue still left or to regenerate new cartilage isn't new.

Previous studies have been able to show that the body does form fibrous cartilage on the damaged joint surface. But it's not exactly the same as the original tissue, so the next question is: how well does it hold up under load and pressure? In other words, how functional is this treatment approach?

A recent study from Australia suggests changes in the cartilage do occur. The results showed that patients were able to generate some articular cartilage but not back to a normal amount. The lateral side of the knee still had more normal (and thicker) articular cartilage than the medial side.

Changes were visible at the six month check-up. Improvements continued to be seen at the 12 month and 24 month follow-up appointments. Knee function was also significantly improved. Further study will be done to see if the joint cartilage reaches a level close to normal.

Reference: David A. Parker, FRACS, et al. Articular Cartilage Changes in Patients with Osteoarthritis After Osteotomy. In The American Journal of Sports Medicine. May 2011. Vol. 39. No. 5. Pp. 1039-1045.