Overall, 1,390 participants had already been diagnosed with knee osteoarthritis, 3,284 did not have the disease but were at risk of developing it, and 122 did not have osteoarthritis or related risk factors.
Weiss analyzed X-rays to determine the severity of patients' arthritis and used the health records to gather information on their BMI and pain levels during everyday activities.
She found that patients with a higher BMI reported more pain, even after adjusting for the severity of their joint damage. For each category of arthritis severity, pain scores were substantially higher among obese patients than among normal-weight patients. Scores for overweight patients fell somewhere in the middle.
Even though osteoarthritis is a progressive disease and its effects are irreversible, losing weight should help reduce pain related to the condition, Weiss wrote online June 17 in Rheumatology.
Losing weight could jump-start a healthy cycle, Weiss said: a decrease in body weight could lessen pain, which in turn might make people more likely to take on more physical activity, resulting in even more weight loss.
It might be difficult for a person who is already experiencing a high level of pain to become active in order to lose weight, however. Weiss suggested trying to lose the weight before starting exercise.
"It is easier to lose weight through dietary changes than through exercise. Small changes can sometimes make big differences," she said. "For example, drinking water rather than cola or finding ways to increase activity that will become a habit, like parking further from the store entrance or taking stairs instead of an elevator."