Can the Knee Grow New Cartilage After Osteotomy?

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.

There could be a tendency toward a flat foot on that side putting the knee at an angle that increases pressure on the medial side of the joint (closest to the other knee). The angle of the knee itself is sometimes toward a knock-knee position creating the same type of medial load on the joint.

Or there could be a change at the hip that alters knee joint alignment. Any anatomic change that contributes to uneven wear and tear on the joint can result in osteoarthritic damage to the joint lining (called the articular cartilage. Pain from this unicompartmental osteoarthritis can be very limiting.

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?

Special MRIs with dye that seeps into the cartilage and first layer of bone were used to examine the knee joints of 10 patients (eight men and two women). They all had a medial opening wedge high tibial osteotomy (HTO). Baseline images were taken before surgery. Images were repeated after surgery at six months, 12 months, and 24 months. Other test measures of knee function were also recorded (using the Knee Injury and Osteoarthritis Outcome Score or KOOS).

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.

It's possible that continued changes occurred after the 24 month mark. Further study will be done to see if the joint cartilage reaches a level close to normal. Patients in this study were kept nonweight-bearing for three months after surgery.

It wasn't until they started walking on the leg that measurable changes in the cartilage were observed. Exactly at what point between three and six months the changes started developing remains unknown and a topic for future study. The study was also fairly small (10 patients) so it will be necessary to repeat the study with a larger number of people.

For now, it appears there is a trend toward cartilage regeneration and recovery using a tibial osteotomy treatment approach for painful unilateral knee joint osteoarthritis. Improving joint dynamics and evening out the biomechanical load on the joint is possible with this surgical approach.

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.

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