Prospects after two knee surgeries.

? I am 50 years old, and have been running for 30 years on the paved streets of New York City. I run 40 miles a week, usually 6 or 7 miles at 7:00 pace. I compete in 5Ks and 10Ks at about 5:50 pace. I do speed work at this pace eight months out of the year, and usually try to work in a 10- or 12-mile run every few weeks.

In 1997 I had arthroscopic knee surgery for a torn meniscus in my left knee. After a few months I was back to normal pace and distance. My left knee is fine today, but this week I had the same surgery on my right knee. For the first time, I harbor doubts that I'll be able to continue indefinitely, and would like to know your thoughts on my future running and competing. Will I damage my knees further, and can I expect recurring injuries in a few years?

Eddie Arbeiter, New York, NY

Don't let the history of two knee surgeries be a reason for despair. Speak to your orthopedic surgeon and find out the quality of the articular hyaline cartilage on your femoral, tibial and patellar sides. That's the coating of the bones around the knee. If there are exposed bone patches, you might have to cut back on your running. If the coating is intact, then keep on trucking.

Rob Meislin, MD, New York, NY

The critical issue isn't whether you've had the surgery, but what the findings were: do you have arthritis? What was the status of the articular cartilage? Based on the answers to these questions, your orthopedic surgeon can make activity recommendations. There is a multitude of low-impact aerobic activities you may try: bicycling, swimming, rowing and cross country skiing come to mind. But none of that may be necessary if all that arthroscopy revealed was grade one or two chondromalacia, which is a softening of the cartilage.

G. Klaud Miller, MD, Evanston, IL

Let me first say that I am impressed by your ability to run as often and as long as you have--and with much skill. The distances and speeds you've run are what most of us have only dreamed about.

It seems like you may be neglecting to crosstrain, which is an important aspect of a running regimen that helps make injury less likely. If your surgeon advises that you have a lot of wear and tear on your knee, I urge you to incorporate crosstraining into your routine. I also would add that as a general principle, we don't wear out so much as "rust out." If you don't have substantial knee disease, avoiding running will not be necessary, though after 50 slowing down a bit and easing up on the mileage may be a wise thing to do.

Larry D. Hull, Centralia, WA