You might not want to rush into knee surgery. Physical therapy can be just as good for a common injury and at far less cost and risk, the most rigorous study to compare these treatments concludes.

Therapy didn’t always help and some people wound up having surgery for the problem, called a torn meniscus. But those who stuck with therapy had improved as much six months and one year later as those who were given arthroscopic surgery right away, researchers found.

“Both are very good choices. It would be quite reasonable to try physical therapy first because the chances are quite good that you’ll do quite well,” said one study leader, Dr. Jeffrey Katz, a joint specialist at Brigham and Women’s Hospital and Harvard Medical School.

He was to discuss the study Tuesday at an American Academy of Orthopaedic Surgeons conference in Chicago. Results were published online by the New England Journal of Medicine.

A meniscus is one of the crescent-shaped cartilage discs that cushion the knee. About one-third of people over 50 have a tear in one, and arthritis makes this more likely. Usually the tear doesn’t cause symptoms but it can be painful. Nearly half a million knee surgeries for a torn meniscus are done each year in the U.S.

The new federally funded study compared surgery with a less drastic option. Researchers at seven major universities and orthopedic surgery centers around the U.S. assigned 351 people with arthritis and meniscus tears to get either surgery or physical therapy. The therapy was nine sessions on average plus exercises to do at home, which experts say is key to success.

After six months, both groups had similar rates of functional improvement. Pain scores also were similar.

Thirty percent of patients assigned to physical therapy wound up having surgery before the six months was up, often because they felt therapy wasn’t helping them. Yet they ended up the same as those who got surgery right away, as well as the rest of the physical therapy group who stuck with it and avoided having an operation.

Surgery costs about $5,000, compared with $1,000 to $2,000 for a typical course of physical therapy, Katz said.