About 700,000 Americans each year undergo surgery to repair a torn meniscus in their knee. The procedure, called arthroscopy, has increased by 50 percent in the past 15 years, according to David Felson, M.D., a rheumatologist and epidemiologist at the Boston University School of Medicine.

Yet research going back more than a decade shows that the procedure often offers little or no benefit, needlessly exposing patients to risks of infection and other side effects, plus wasted health-care dollars. The estimated annual price for all of that surgery is $4 billion.

Here's why doctors continue to offer the procedure, and what you should do instead.

No Better Than Sham Surgery

The older you are, the more likely you are to have torn your meniscus, cartilage in your knee that functions as a shock absorber in the joint. As many as 60 percent of adults over age 70 have a torn meniscus, according to the American Medical Society for Sports Medicine.

And if you have chronic knee pain, your doctor may order an imaging test such as an MRI and, if he sees a tear, recommend arthroscopic knee surgery, which involves repairing the damage through two tiny incisions.

But back in 2002, a study in the New England Journal of Medicine found that arthroscopic knee surgery to repair a torn meniscus was no more effective than placebo surgery in which doctors cut open the skin and simulated a repair.

Since then, other studies—including two 2013 trials also published in the NEJM—found that arthroscopic knee surgery was no better than physical therapy or placebo surgery.

Why would doctors continue to recommend a procedure proven to be ineffective for many people? Often simply because it takes many years for doctors to give up old therapies after studies show them to be ineffective or dangerous, says Vinayak K. Prasad, M.D., an assistant professor of medicine, public health, and ethics at the Oregon Health & Science University and co-author of “Ending Medical Reversal."

Sometimes doctors may simply be unaware of new evidence, Prasad points out. And some healthcare providers may stick with outdated procedures simply because they’re lucrative or fit their view, Prasad says.

What to Do Instead

If you’re under 50 and your torn meniscus stems from a sports injury, arthroscopic knee surgery can be reasonable.

But if you’re older and suffer from osteoarthritis, it won’t help. “It only fixes one small part of the problem and doesn’t address the pain and inflammation that affects the entire knee joint,” Felson says.

You’re better off with measures like over-the-counter anti-inflammatories and physical therapy, he says.

Read more about how to treat hip and knee pain.