Q: I'm looking into the possibility of putting off a knee replacement by either having an osteotomy done or a unicompartmental knee replacement. Which one is a better choice?

A: Degenerative joint disease (osteoarthritis) often causes wear and tear on just one side of a single knee joint. This usually happens when there is a problem with knee joint or lower leg alignment. Because the knee is either in a position more toward knock knees or perhaps the opposite, bow legs, pressure and load are shifted from the midline more toward one side of the joint or the other.

Over time, this uneven weight distribution takes its toll on the joint. But why replace the whole joint when only part of the joint is damaged? Instead, patients can benefit from an osteotomy or a unicompartmental joint arthroplasty (replacement).

With an osteotomy, a wedge or pie-shaped piece of bone is removed from one side of the knee. The goal is to shift the patient's body weight off the damaged area to the other side of the knee. This makes better use of the cartilage that is still healthy. With a unicompartmental implant, only the side of the joint that's damaged is removed and replaced with a metal joint implant.

There are some advantages and disadvantages to the osteotomy approach to unilateral (one-side of the joint) arthritis. As mentioned, it can help patients put off joint replacement. And unlike joint implants, with an osteotomy, it's still possible to engage in high-impact activities like jumping and running. Implants are not as durable and thus limit activities of this type.

The disadvantage of osteotomy is that there is a risk of continued knee pain. It's a trade-off: with osteotomy, there is a greater activity level but more discomfort. With a unicompartmental (or complete) joint replacement, the pain is gone (or very minimal) but activities are limited.

Most of the time, surgeons recommend osteotomy for younger, more active patients. Unicompartmental knee arthroplasty is a better choice for older, more sedentary adults. As young adults who opt for an osteotomy grow older, they still have the choice of a joint replacement later in life, thus extending the life of the joint for as long as possible.

Reference: Aaron Gardiner, MD, et al. Osteotomies About the Knee for Tibiofemoral Malalignment in the Athletic Patient. In The American Journal of Sports Medicine. May 2010. Vol. 38. No. 5. Pp. 1038-1047.