Body mass and osteoarthritic pain: results from a study in general practice

To define the relationship between BMI and pain due to osteoarthritis (OA) of the hand, hip, and knee in patients seen in general practice; to evaluate if overweight is related to co-morbidity and education, and influences the prescription patterns of GPs.

2,764 Italian GPs recruited 10 consecutive patients with symptomatic OA, diagnosed according to the ACR criteria. Pain intensity on a visual analogue scale, BMI, years of formal education, comorbidities, pharmacological and non-pharmacological interventions, and referral to specialists were recorded.

The most painful joints were the knee in 12,827 patients (53.6%), the hip in 5,645 (23.6%), and the hand in 5,467 (22.8%). A BMI indicative of overweight or obesity was found in 74.8% of men and in 68.3% of women. Mean BMI was higher in knee OA (27.9±3.9), in generalised OA (27.5±4.2), and hip OA (27±3.7) than in hand OA (25.5±3.4). The prevalence of obesity for hip and knee OA was higher than that reported for the general Italian population. Obesity was an important risk factor for pain in all OA localisations. Co-morbidities and lower education were associated with obesity and more intense pain (p<0.0001). Obesity and overweight were less frequent in institutionalised patients.

Our study confirms that more than two thirds of Italian patients with symptomatic OA seen by GPs are overweight or obese. Obesity is clearly associated with OA pain, a finding which is probably underestimated by GPs who are not used to modulate treatment and specialist referral according to patients' BMI.