Sore, aching knees, hips, fingers, backrest. Pain after excessively much activity. Pain after overly little. Eventually, almost everyone gets degenerative arthritis. Sometimes it’s the result of decades of wear-and-tear on the shock-absorbing cartilage that prevents bone from rubbing against bone. Sometimes it starts sooner, after an injury to the knees or other joints. “By the age of 70, nearly everyone…