Confusions About Knee Meniscectomy

There's a lot of confusion right now about the best treatment for tears of the knee meniscus. For sure, we know that removing this C-shaped cartilage in the knee is a bad idea. That just leads to degeneration of the joint and painful arthritis. Repairing the damage and letting the body heal has proven to be a much better alternative.

But even with a partial meniscectomy (removing the ragged edges) and/or repair (stitching the rest back in place), there are still a fair number of patients who do better than others. Or to turn that around, there's quite a few patients who don't do as well as others.

The natural question is why not? What gives some patients good outcomes while others still end up with knee arthritis? Reports from various studies are all over the place on this one.

One study says poor outcomes are because the person was older and had a certain pattern of injury. Another says, no, it's because patients have poor alignment and a high activity level.

Other factors that might play into positive versus negative results include meniscal tears as a result of degenerative disease rather than injury, sex (male versus female), and meniscal tears that occur along with injury to the anterior cruciate ligament (ACL) (ligament inside the knee).

Basically, there is a lack of uniform evidence about what contributes to a good result and what doesn't. To help sort through all the possible factors that might predict who will have a good result and who won't when having meniscus surgery, the authors of this report performed a systematic review.

A systematic review means they looked at all of the studies done so far, found the ones with the highest level of evidence, and analyzed the data to come up with some statistically sound conclusions.

We wish we could tell you that the result was clear and now we know the answer. But what they found was that the poor study designs used, the low quality of research, and the fact that so many researchers left out important data means we still don't have a firm grip on why some patients outperform others after meniscectomy.

Let's take a closer look at what they summarized from the findings of the systematic review. The first is age. Older folks do indeed have a greater risk of degenerative meniscal tears. And it doesn't take much for the stiff, dry cartilage to snag on a bone spur or other arthritic lesion in the knee joint and then tear. This type of tear does seem to have a poorer outcome compared to young athletes who injure their knees while playing sports.

What about sex (gender) as a risk factor? Are women more likely to have a poorer outcome? Or do they just complain more than men? As it turns out, it looks like sex alone is not the main determinant. Activity level (greater demand and higher level of sports participation) and type of surgery had a greater influence on the development of arthritis after meniscectomy.

And some of the factors appeared to have more to do with risk factors for osteoarthritis than for meniscectomy. For example, patients with hand arthritis were more likely to develop osteoarthritis in the knee. Genetics and hereditary factors probably play a more important role than meniscal injury.

Obesity defined as a body mass index of 30 or more was an independent risk factor for both osteoarthritis of the knees and poor outcomes after meniscal surgery. That means being overweight puts people at risk for both knee arthritis (with or without a meniscectomy) and poor function after meniscectomy.

There's been some discussion around the idea that maybe removing one particular side of the meniscus affects the results more than the other. But the results were variable there, too. Some studies measured the amount of meniscus removed.

Others reported on the contact area and force load based on which side was damaged and repaired. It looks like the dynamic loading pattern differs from patient to patient due to alignment and surface structure (how curved the meniscus and joint surface are and how well they match up).

There is agreement on one thing: patients with a torn meniscus and ruptured anterior cruciate ligament (ACL) do have worse results than patients with just a torn meniscus. That seems to make sense at first glance.

But exactly why an ACL deficiency makes matters worse isn't entirely clear. It could be that without a strong ACL, the loss of the meniscus magnifies the problem. Or it could simply be the effect of the loss of stability on the knee joint without the ACL.

And this is where it gets sticky because there's some evidence that the type of meniscus tear and how it is treated (e.g., bucket handle tear that is repaired versus removed) enters into the results when there's both a meniscal tear and damage to the ACL.

Finally, what about skipping surgery and just doing an exercise program? Does that work any better? There aren't very many studies comparing these two treatment approaches. But the one study that was included looked at just patients with degenerative meniscal tears.

One group had surgery with exercise afterwards. The other group just did the exercises. The results (measured in terms of activity level, pain, and motion) were the same between the two groups. Follow-up was limited to six months so there's no report on the long-term results.

After all the data was examined, the authors summarized by saying that clearly there's a lack of uniformity within the literature. They found it very difficult to really make any firm conclusions.

They end by calling for higher levels of evidence and more prospective cohort studies. Cohort studies observe what happens over time rather than putting patients in different treatment groups and seeing how the results compare. Using this research design yields the highest level of evidence.

Reference: Michael J. Salata, MD, et al. A Systematic Review of Clinical Outcomes in Patients Undergoing Meniscectomy. In The American Journal of Sports Medicine. September 2010. Vol. 38. No. 9. Pp. 1907-1916.