Knee replacement surgery may significantly ease pain and improve leg function and quality of life in patients with osteoarthritis or rheumatoid arthritis (RA), a recent study suggests. While surgery doesn’t restore the same level of comfort and function patients had in their younger years, before they developed arthritis, the authors write that knee replacement can serve as a time machine of sorts, turning back the clock to a point when patients were less disabled.

Researchers examined how much pain improved from six months before knee replacement until six months afterward in 315 patients with osteoarthritis, the most common form caused by wear and tear on cartilage, and in 834 patients with RA, an immune system disorder that causes joint swelling. “The vast majority of patients had their symptoms improve dramatically from the surgery, but this procedure is not a cure and RA patients…