Each year, an estimated 700,000 arthroscopic surgeries are done on the knees of middle-aged and older Americans to relieve chronic knee pain caused by osteoarthritis or a torn meniscus, the cartilage that cushions the knee bone and protects it from wear and tear.
The evidence for such surgery has always been weak — only one clinical trial has reported that it benefits patients — yet many surgeons continue to perform the procedure.
Arthroscopic knee surgery is considered minor surgery, but it is not without risks, including infections and blood clots.
On Tuesday, a team of Danish and Swedish researchers released a major new systematic review of nine previously published clinical trials that compared arthroscopic knee surgery to either exercise treatment or “placebo surgery” (faked surgery in which the part of the procedure thought to be therapeutically necessary is not done). The studies involved a total of 1,270 participants aged 49 to 62.
The reviewers found that both exercise and arthroscopic surgery had a small effect on reducing knee pain, but that the benefit from the surgery disappeared after six months.
The pain-relieving benefit that the patients received from arthroscopic surgery for a few months was comparable to taking an over-the-counter pain medicine and significantly less than the effect seen from exercise therapy for knee osteoarthritis, the reviewers point out.
As for improvements in physical function, no difference was found between the treatment groups.
Not without risk
The review did find that arthroscopic knee surgery was associated with significant and serious health risks, including an increased risk of infection, blood clots in the legs and lungs, and death.
Of those risks, developing a blood clot in the legs was the most common — 4.13 occurrences per 1,000 procedures. The risk of death was slightly less than 1 per 1,000 procedures.
The reviewers also point out that arthroscopy is associated with a particular long-term risk: an increased likelihood of developing osteoarthritis.
“Patients with previous knee surgery undergo total knee arthroplasty [replacement] at a significantly younger age than do patients without previous knee surgery,” they note.
At a tipping point
All these findings taken together “do not support the practice of arthroscopic surgery for middle-aged or older patients with knee pain with or without signs of osteoarthritis,” the reviewers conclude.
Degenerative meniscal tears (ones caused by years of wear and tear rather than by a single injury) and other structural abnormalities that often show up on diagnostic knee images are just as likely to appear in the knees of middle-aged and older people who have no knee pain as those who do, they add.
Thus, a patient’s knee pain may have nothing to do with the degenerative meniscal tear, and repairing that tear will do nothing to relieve the patient’s symptoms.
“We may be close to a tipping point where the weight of evidence against arthroscopic knee surgery for pain is enough to overcome concerns about the quality of the studies, confirmation bias, and vested interests,” writes Dr. Andy Carr, an orthopedic surgeon and professor of orthopedics at Oxford University in the United Kingdom, in an editorial that accompanies the study. “When that point is reached, we should anticipate a swift reversal of established practice.”