Dear Dr. Roach: I am a highly active 74-year-old female. I walk a mile and a half every morning (my dog insists), then do two step-aerobic classes with weights, two serious weight workouts with a trainer, 1-3 miles on an elliptical walker and 2-4 hours of horseback riding, plus miscellaneous activities and yard work each week.

My left hip is getting a bit wonky. The X-ray results are “moderate degenerative arthritis.” I have lost maybe 20 degrees of outward rotation. Right now, the discomfort level is comparatively minor; a couple of Advil work. Generally, the arthritis doesn’t interfere with activities, I just get achy.

My question is, when do you decide to replace a joint? Can you wait until age 80 or older to do a replacement? Some of my friends say you need to do it before you get “too old.” I do not want to have to reduce my activity level when I enjoy being active and keeping fit, particularly when I see so many of my contemporaries becoming less and less mobile and healthy. Is sooner really better than later? — A.S.

Answer: There is no upper age limit on a joint replacement, and healthy people of any age may safely benefit from a joint replacement.

I refer my patients to the surgeon only when arthritis is keeping them from doing the activities that they want to do, or when the pain cannot be controlled. It doesn’t sound like either of those is the case for you, so you don’t need to rush to see the surgeon. I recommend you continue to enjoy your activities and periodically go through an honest self-assessment.

You do an impressive number of activities. You need to be most careful with your equestrian activities, because even experienced horsewomen (and men) can get injured, and an injury could significantly decrease your ability to exercise. I am sure that all your activities are helping to keep your muscles strong and maintaining your joint function, despite the arthritis. Stopping exercise, even for a few weeks, could have a severe affect on your function.