Osteoarthritis and Meniscus Tears, Does Knee Arthroscopy Help?

Man experiencing joint pain while on the beach. Jeannot Olivet/ E+/Getty Images

Patients with osteoarthritis (OA) of the knee will often find out that they have a meniscal tear. At that point a common question is, shouldn’t I get it fixed? As with any medically related question, this one does not have a simple straightforward answer.  Knee arthroscopy, or a knee ‘scope’, is the traditional minimally invasive technique used to treat meniscus tears. Most meniscus tears are treated with a partial meniscectomy, where the torn part of the meniscus is trimmed and removed.

The situation changes significantly when a meniscus tear is found in the setting of osteoarthritis.

The first issue, is that if a person with OA has a meniscus tear and knee pain, it is very likely that the meniscus tear is not the cause of the knee pain. A study in 2003 done by Boston Medical Center and the Boston VA Hospital found that approximately 76% of asymptomatic people with knee osteoarthritis have meniscal tears. That number rises to 91% for people that have symptomatic OA of the knee. This is often a surprising fact for patients. From these statistics we can infer that in people with meniscal tears and osteoarthritis, often enough treating the meniscal tear may not help their overall symptoms, since the meniscus wasn’t the pain generator in the first place.

In fact, a number of randomized controlled trials have illustrated that very point. The most impressive of these trials was a double-blind study comparing surgery versus a sham procedure out of Finland, published in 2013 in Journal of Bone and Joint Surgery.

Patients were randomly split into two groups, one underwent surgery with partial removal of their meniscus, and the other underwent a ‘sham’ procedure where the incisions were made and the knee was simply washed out with a lot of fluid and no meniscectomy was done. Double blind means that neither the patient nor the doctor evaluating the patients after surgery knew which group the patient belonged to.

The findings of this trial were quite striking. In this group of patients with meniscal tears and osteoarthritis, there was absolutely no difference between the two groups at any time point from before surgery through 1 year after surgery. Both groups showed statistically significant improvement in pain and function compared to the pre-surgery evaluation. This highlights an important point. Surgery in general has a very high placebo effect. This makes studying the effects of surgery difficult, since in most cases it is impossible to have a sham-surgery study group. This Finnish study, would have been difficult to impossible to carry out in the United States, since the U.S. has much tighter restrictions with what is deemed a safe and ethical study design.

A recent meta-analysis of 9 randomized trials published in the British Medical Journal echoed the results of the Finnish Study. The meta-analysis found that on average the improvement from surgery with regards to pain was approximately 2.4mm when measured on a 100mm visual analog scale.

This is a slightly confusing way to depict pain; I’ll do my best to explain it. Picture a ruler that’s 100mm long, all the way on the right side (at 100mm) lies a big frowning face with tears that signifies the worst imaginable pain a patient can be in, all the way on the left side at 0mm is a big smiling happy face with absolutely no pain. 2.4mm on that scale is a fairly small amount.

Typically a difference of 15-20mm is suggested as clinically relevant. This minimal improvement in pain also disappears at somewhere between 1 and 2 years. The study also notes that will the pain benefits of arthroscopy for knees with osteoarthritis are negligible, the risks (however small) are undoubtedly present. The risks of deep venous thrombosis (blood clots, typically in the legs) are on average 4 in 1000. Other risks of surgery include pulmonary embolism (blood clots in the lungs which can be fatal), infection and death.

These studies do a pretty good job of providing evidence for what to do, or more accurately what not to do, for patients with severe OA of the knee and a meniscal tear. The harder question is what to do for patients with mild to moderate osteoarthritis of the knee, and an acute tear of the meniscus. Or patients with osteoarthritis of the knee, and symptoms of locking/catching that are very specific to meniscal injury. The answers to these questions are less difficult to find, and more depend on the particular judgment of the doctor and require a thorough conversation between doctor and patient. 

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