ProHealthNetwork.com, By Eric Sabo, Healthology

President Clinton and President Bush may have their political differences, but both are avid runners. Shortly before his second term, however, the current President gave up his favorite exercise because his knees "had finally had it," as he told reporters last year. Now, President Bush can be found zipping around Washington and his Texas ranch on a mountain bike.

Knee pain does not have to be the end of physical activity, explains Lynn Millar, PhD, assistant director and associate professor of physical therapy at Andrews University. Like the president, you can keep active by switching to exercises that have less of an impact on your knees. This holds true even if you have arthritis. The key, Millar says, is supplemental conditioning, where you work to strengthen your lower body to withstand the wear and tear of whatever exercise you ultimately choose.

What activities tend to be hardest on the knees?

The ones that involve excessive flexing, especially with weights, such as a full squat. Or if there is any type of exercise that involves twisting, such as when you jump, twist and plant your feet, like in basketball.

Some jumping activities, or plyometrics, are also very hard on the knee, and you'd have to judge as to which ones would not involve a twisting or a really deep knee bend. Low plyometrics might not be too bad, even something like jumping rope or things on a trampoline, depending on how stable your knee is.

Any activity where there's a lot of twisting and landing motions would also be very difficult on the knee. Tennis, racquetball, and soccer, for example.

Is jogging hard on the knees?

Jogging actually is not hard on the knees. A lot of people say, "Oh, it's going to cause arthritis," but running or jogging hasn't been shown to increase the incidence of arthritis. The thing that leads to long-term complications are knee injuries. So, if you've injured the knee and are jogging, then it can be hard on the knee. An injury is one of the biggest predictors of getting arthritis.

I would say if you run cross-country on uneven surfaces, then it may be hard on the knee; if you have some inherent misalignment, some problem that causes problems with almost anything. But otherwise, jogging isn't really that hard on the knee.

What exercises tend to be easier on the knees?

Swimming, except for butterfly stroke, is fairly easy on the knees. Walking is excellent because you don't have high impact. Jogging isn't bad if the person hasn't had an injury. Bicycling is not that bad on the knees. Any activity where there's a reduced impact or you don't have to worry about changing motion.

Is knee pain caused by overuse or by the chance of injury?

Generally, it's not overuse. You're more likely to injure the knee because of rapid plants and changing of motion. These types of activities where you're either jumping and landing or moving and trying to do a rapid change of motion cause more stress on the knee, which can cause an ACL (anterior cruciate ligament) injury. But in smaller amounts, too, these activities may damage the cartilage and the meniscus that helps protect the cartilage.

For people who have bad knees and want to switch to these safer exercises, should they still try to slow down?

It depends on how bad their knee is. Unfortunately, that's one of those gray areas that you have to say, "What was the injury to knee, how bad is it afterwards?" That will give you an idea of what sort of activities you can still do and how much you have to decrease the intensity.

The thing that will also help determine the intensity and what you can do is how well you rehab it after an injury, and how good you are at doing supplemental conditioning. A lot of injuries seem to be due to the weakness of certain muscles, either right around the hip muscles that help to stabilize the lower back and hip or even some weakness in the hamstrings and quadriceps.

It may. What I've done is gone walking every other day rather than running every single day. It's using your muscles slightly differently and decreasing impact. We think it's important to do a variety of activities.

A lot of the recent research is showing that weakness in the hips, such as the hip abductors (the ones that pull your leg away from midline) and your rotators (the ones that turn your thigh in and out) is predictive of your chance of injury, even down at the knee.

When those muscles can't contract properly, that allows that leg to drift in towards the midline and put you into an awkward position. A study last year on cross-country runners found those who had a greater chance of injury were those with weak muscles around the hip. So, it's not just strengthening around the knee, but also the core muscles, like your back, abdomen and hip muscles, in addition to your quadriceps and hamstrings.

A very simple way to strengthen those quads is what I call a wall sit. The person is going to take about two steps away from the wall and then lean back so that their back is supported by the wall. Then they're going to slide down until they're almost sitting in a chair, but not quite, to 90 degrees. Then they can slide back up.

What advice do you have for people who have bad knees who want to keep active?

If they're not doing a supplemental conditioning program, they need to realize that just doing an activity by itself will not necessarily strengthen all the muscles that you need to support the different joints. A supplemental training program doesn't have to be real big or complicated, but it is very, very important. And that usually involves strengthening the core muscles: the hip, lower back, abdomen and any of the muscles around the joints that are being used.

Supplemental conditioning is probably one of the biggest keys to being able to maintain an activity or to get back to it.

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