(Reuters Health) - So-called arthroscopic knee surgery is becoming a less common treatment for adults with torn cartilage or painful arthritis as a growing body of evidence shows little benefit from these operations, a U.S. study suggests.

Researchers examined data on all surgeries done on patients 18 and older in Florida from 2002 to 2015, including a total of 868,482 arthroscopic knee procedures. Overall, rates of these operations declined 23 percent during the study period, with sharper decreases after 2008.

Many experts believe doctors don’t change the way they treat patients when studies show those treatments don’t work, and knee arthroscopy is often cited as an example, said study author David Howard of Emory University in Atlanta.

“There was some evidence that use of arthroscopy was declining, but this study shows that the decline was large and has been sustained,” Howard said by email. “I think patients can be reassured that doctors reacted to the evidence.”

During this operation, a surgeon makes a small incision in the knee and inserts a tiny camera called an arthroscope to view the inside of the joint, locate and diagnose the problem, and guide repairs.

While this is minimally invasive, it’s not risk-free. Patients receive anesthesia, which in any surgery may lead to complications such as allergic reactions or breathing difficulties. In addition, this specific knee procedure has the potential to damage the knee or trigger blood clots in the leg.

Multiple studies have shown that knee arthroscopy isn’t any better than non-operative treatments for conditions like arthritis, torn cartilage and knee pain, Howard notes in JAMA Internal Medicine. But evidence to date hasn’t offered a clear picture of how much doctors and patients are avoiding the operations as a result.

Between 2002 and 2015, knee arthroscopy rates in Florida declined from 449 procedures for every 100,000 adults in the population to 345 procedures for every 100,000 adults, the current study found.

Declines were steeper after 2008, when a second major trial was published that failed to detect a difference between surgery and “medical management,” which might include things like medications to ease pain or inflammation or use of heat or ice, or physical therapy.

These declines in surgery happened even as the prevalence of knee osteoarthritis among U.S. adults more than doubled from 6.6 percent in 1999 to 14.3 percent by 2014, Howard writes.

The study wasn’t a controlled experiment designed to prove what factors might have influenced any declines in these surgeries or whether or how patients might have different health outcomes as a result. And it only included data from Florida.

Still, the results suggest that doctors and patients are getting the message that these operations aren’t the best approach for wear and tear that contributes to knee pain as people age, said Andrew Carr, a researcher at the University of Oxford in the UK who wasn’t involved in the study.

“Rest and time are often very helpful,” Carr said by email. “If symptoms persist then other treatments including physiotherapy and the use of anti-inflammatory medication may be of benefit.”

There are still, however, far too many operations being done on patients who may not benefit and may be harmed instead, said Jonas Bloch Thorlund, a researcher at the University of Southern Denmark who wasn’t involved in the study.

“There is still room for improvement,” Thorlund said by email.

SOURCE: bit.ly/2xBHzt9 JAMA Internal Medicine, online September 24, 2018.