How does obesity affect knee pain?

Carlos M. Alvarado, MD
Orthopedic Surgery
Obesity is directly related to knee pain. The knee endures an incredible amount of stress daily. Between 2.5 and 7 times  body weight is absorbed through the knee joint with each step. That means even small changes in body weight can have a drastic effect on knee function.

The increasing prevalence of overweight and obese Americans among all age groups, keeps orthopedic surgeons busy operating on damaged knees. In fact, a study suggested that the overweight and obesity epidemic was driving the need for total knee replacements at a rate that outpaced the need for hip replacements. Doctors have seen the uptake in the need for knee replacement surgeries in people with a body mass index, or BMI, of 25 or greater.
Obesity plays a major role in pain in general, but it has some of its largest impact on knee pain. The most common cause of chronic knee pain in the U.S. is related to osteoarthritic changes, commonly referred to as arthritis. In simple terms, this is the general wearing down of the knee over time. When patients are obese it places a greater deal of stress on the knee joint, increasing the rate of deterioration exponentially. This will lead to worse knee pain sooner than in people with similar lifestyles but less weight. Obesity is also suspected to play a role in worsening inflammation, which is a major component of joint pain.
Scott D. Martin, MD
Orthopedic Surgery
Carrying extra weight is directly related to knee pain. One review article found that obesity (defined as having a body mass index of 30 or above) leads to pain, limits activity, and increases the risk of needing a total knee replacement. Another study of 5,700 Americans over age 60 showed that the more obese a person was, the more likely he or she was to experience knee pain. About 56% of severely obese people had significant knee pain, compared with 15% of people who were not overweight.

Such findings are not surprising when you consider that with each step on level ground, you put one to one-and-a-half times your body weight on each knee. So a 200-pound person can put 300 pounds of pressure on each knee with each step. The burden is even higher when you go up and down stairs (two or three times as much weight) or squat (four or five times). So if you're 50 pounds overweight, the simple act of going downstairs and squatting to move clothes from the washer to the dryer puts hundreds of extra pounds of force repetitively on your knees.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.