How do I prevent my knees from hurting when I descend stairs?

If it’s any comfort, you have company. Most people with knee arthritis — meaning some degeneration of the cushioning cartilage in the joint — experience pain when they go down stairs, even if their arthritis is otherwise mild, said Dr. Kevin J. Bozic, an orthopedic surgeon at the University of California, San Francisco. More so than climbing stairs, descending them places great force on the knee and, in particular, the patello-femoral joint, the portion of the knee beneath the kneecap, he said.

This discomfort is magnified if you have weak quadriceps or thigh muscles, he added, since the force that might otherwise be absorbed by those large muscles moves through the knee instead. So to strengthen your quadriceps, try straight leg raises, Dr. Bozic said. Simply lie on your back with one leg bent. Lift the other leg, straightened, at least six inches off the ground; tighten the thigh muscles and hold for a few seconds. Lower and repeat several times. Then do the same exercise with the other leg. Your physician or an athletic trainer can suggest other safe exercises that target those muscles.

Avoid prolonged sitting, too, said Dr. Freddie H. Fu, a professor and chair of orthopedic surgery at the University of Pittsburgh Schools of the Health Sciences, since uninterrupted sitting leads to stiffness that aggravates the pain of going down stairs.

And if all else fails, turn around, Dr. Bozic said. “Descending stairs backwards reduces loads across the knee joint,” he said. According to a 2010 motion-capture study, the forces generated when descending backward migrated toward the hip rather than the knee when people go backward. “Just don’t fall down,” Dr. Bozic warned.