Dr. Jevsevar, an orthopedic surgeon in St. George, Utah, said he hoped the study would spur research to better identify patients who should have surgery.

“Are there operations that are done that do not need to be done? I’m sure that’s the case, but we don’t know the magnitude,” he said. “We still think there’s benefit in arthroscopic meniscectomy in appropriate patients. What we need to define in the future is what’s the definition of appropriate patient.”

One factor is whether pain is caused by the torn meniscus or something else, especially osteoarthritis, which often accompanies tears. Another possible consideration is whether mechanical knee function is affected.

“Take 100 people with knee pain; a very high percentage have a meniscal tear,” said Dr. Kenneth Fine, an orthopedic surgeon who also teaches at George Washington University. “People love concreteness: ‘There’s a tear, you know. You have to take care of the tear.’ I tell them, ‘No. 1, I’m not so sure the meniscal tear is causing your pain, and No. 2, even if it is, I’m not sure the surgery’s going to take care of it.”

Dr. Fine added: “Yours truly has a meniscal tear. It just causes pain. I’m not having any mechanical symptoms; my knees are not locking. So I’m not going to let anybody operate.”

He likened the recent studies to attempts to educate people that “it’s not really good to take antibiotics for the common cold. There’s a lot of pressure to operate. Financial, obviously. But also, if a primary care doctor keeps sending me patients who are complaining of knee pain and I keep not operating on them, then the primary care doctor is going to stop sending me patients.”

The new research builds on a groundbreaking 2002 Texas study, showing that patients receiving arthroscopy for knee osteoarthritis fared no better than those receiving sham surgery. A 2008 Canadian study found that patients undergoing surgery for knee arthritis did no better than those having physical therapy and taking medication. Now many surgeons have stopped operating on patients with only knee arthritis.