Knee osteoarthritis, body mass index and pain: data from the Osteoarthritis Initiative.

Abstract

This study aimed to determine whether BMI increases knee pain as measured from self-reported surveys even when controlling for OA severity as measured by osteophytes and joint space narrowing visible on X-rays. Data available through the Osteoarthritis Initiative (OAI) were analysed, which included a sample of 4769 individuals, to answer the above question regarding OA, excess weight and pain. OA severity was assessed through baseline X-rays on right knees that were scored on a composite quasi-Kellgren and Lawrence grade. Weight was assessed through BMI. Pain was assessed through self-reports of the WOMAC pain subset as well as a 30-day pain severity question based on a 0-10 scale. Data were analysed using SPSS and analyses of covariance (ANCOVAs) were run to examine models adjusted for age, smoking, prior injury, pain medication and Heberden's nodes. Critical alpha levels were set at 0.05. The results reported here confirm that knee pain does increase with OA severity. However, ANCOVA multiple regressions with controls reveal that even when taking into account OA severity, individuals with higher BMIs experience greater pain than individuals with lower BMIs. Weight loss may reduce knee OA pain even if the osteological symptoms are not treated.