Thousands of Americans who undergo a common knee surgery might be making their problems worse rather than better. Researchers who followed patients for 10 years after they received either the actual procedure, arthroscopic knee surgery to trim degenerative cartilage tears, or merely “sham surgery” — a skin incision — for knee pain, found that the surgery provided little or no benefit and was, in fact, associated with accelerated osteoarthritis and higher rates of reoperation. That generally meant a total knee replacement. “I don’t know how I would defend this procedure at all,” said one...