Location of Injury: Knee

Likely Cause: Overdoing it — as in too much jogging or skiing — can aggravate the knees. Sitting for long periods or frequently walking down stairs can make matters worse. Women are especially prone to knee problems. "Their wider pelvises may put more force on the knees," says osteopath Robert Gotlin.

What to Avoid: Activities that put direct stress on the knees, like running, skiing, deep knee bends, squats, lunges, and certain yoga poses. Also avoid stretches that bend the knees too much, like the classic runner's stretch, in which you grab a foot from behind and pull it back toward the body.

What You Can Do: Biking is fine, but raise the seat so your knees don't bend too much. Swimming is a good choice, too — just avoid the breaststroke, because of its bent-knee kick. An elliptical machine is also a smart option, since it puts little stress on the joints.

What Would Make It Better: Try exercises that strengthen and stretch the hip and leg muscles, such as leg presses, moves on a balance board, and hip, buttock, hamstring, and calf stretches (for specific exercises with drawings, go to www.familydoctor.org).