Doctors still slice into arthritic knees, scrape the cartilage, and flush out the joint hundreds of thousands of times a year—even though a major study proved the real surgery works no better than fake surgery. In 2002, surgeon J. Bruce Moseley and his team published a carefully designed study in the New England Journal of Medicine. They took 180 patients with painful knee osteoarthritis who had already tried medicines and other treatments. The patients were randomly split into three groups. One group got the full arthroscopic surgery: the doctor washed out the knee with a lot of fluid, shaved rough cartilage, and trimmed any torn or worn pieces of the meniscus (the soft cushion in the knee). A second group got only the washing (lavage). The third group got a sham, or fake, surgery. Those patients were sedated, the surgeon made the same small skin cuts, and the operating room team made the sounds and motions of real surgery—but nothing ever went inside the joint. Neither the patients nor the people checking their results knew who got the real surgery and who got the fake one. For two full years, researchers tracked pain and how well people could walk and climb stairs. At every check-up, the three groups looked the same. The real operations did not reduce pain or improve function any better than the pretend surgery. The confidence intervals even ruled out any meaningful difference. Patients in all groups felt a bit better, which the researchers attributed to the placebo effect—the power of believing you had a real treatment—plus the natural ups and downs of the condition. At the time of the study, more than 650,000 of these arthroscopic procedures were already being done each year in the United States. Rates of pure “clean-out” surgeries for osteoarthritis later fell somewhat after guidelines advised against them, yet knee arthroscopy (especially for degenerative meniscus tears that often occur alongside arthritis) remains extremely common. Recent data still show hundreds of thousands of knee arthroscopies performed annually in the U.S. alone. The Moseley trial and later similar studies continue to show that, for typical age-related knee wear, the mechanical work inside the joint adds little or nothing beyond the placebo effect and standard non-surgical care.