Lifestyle changes, medication relieve symptoms of BPH

Q: I'm 68. I've jogged regularly for decades, but I've recently developed a touch of arthritis in my knees. Will continuing to run make my knees wear out faster?

A: Having mild arthritis in the knees should not stop you from running. And, in case you were wondering, running probably did not create the problem in the first place.

Like all joints, the knee is where two bones meet. A tough, rubbery substance called cartilage covers the ends of bones. Cartilage serves as a cushion between two bones in a joint.

Osteoarthritis causes cartilage to break down. (I've put an illustration showing the effects of osteoarthritis on the knee on my website, AskDoctorK.com.)

Osteoarthritis can appear in any joint. But the knee is particularly vulnerable because it is a weight-bearing joint that gets a lot of daily wear and tear over the years. Yet not every older person winds up with osteoarthritis.

Why do some people get osteoarthritis while others don't?

In part, it's genetic. If your parents or grandparents had arthritis, you are at increased risk of developing it yourself.

Gender makes a difference: Women have a higher risk for osteoarthritis than men.

Being overweight or obese also drives up risk. The extra weight puts more strain on the joints that must bear that weight.

The knees absorb a lot of force when running, so it's natural to think that running itself can accelerate the natural wear on the joints. But in fact, running appears to have a protective effect against arthritis.

Studies have shown that the average recreational runner has a lower risk of hip and knee arthritis.

There are several possible reasons for the protective effect. First, regular runners tend to weigh less. Second, running may stimulate cartilage to grow, not wear it out. Third, running builds strength in the leg muscles. Strong thigh muscles tend to cushion the joint by absorbing some of the pounding when you run.

What should you do now that you have arthritis?

You should continue regular exercise of your legs to keep the thigh muscles strong. However, if you continue running, it might help to change your terrain.

Softer running surfaces, such as a track at a local school, or a flat and smooth dirt trail, might be a little easier on your knees than running on a sidewalk or street.

If you have pain when you run, consider exercise that keeps leg muscles strong while reducing the impact on your joints. Swimming, cycling and an elliptical cross-trainer are good options.

There are exceptions to this general advice, and I'm one good example. When I was young, the thigh muscle in my right leg was split in a basketball accident. I was in a full-leg cast for months.

Thirty years of jogging on asphalt and concrete surfaces destroyed my right hip - and I had to have a hip replacement.

My left hip was, and is, fine. With the benefit of hindsight, I should have switched to using a cross-trainer many years before I did.

• Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.