Association of weight gain with incident knee pain, stiffness, and functional difficulties: a longitudinal study.

OBJECTIVE: To examine the longitudinal association between significant weight change and change in knee symptoms (pain, stiffness, and function), and to determine whether the effects differ in those who are obese and those with osteoarthritis (OA).
METHODS: Two hundred fifty subjects ranging from normal weight to obese (body mass index range 16.9-59.1 kg/m(2) ) and no significant musculoskeletal disease were recruited from the general community and weight loss clinics and organizations. Seventy-eight percent were followed at ~2 years. Weight, height, and knee symptoms (using the Western Ontario and McMaster Universities Osteoarthritis Index) were assessed at baseline and followup. Any weight loss methods were recorded.
RESULTS: Thirty percent of subjects lost ≥5% of baseline weight, 56% of subjects' weight remained stable (loss or gain of <5% of baseline weight), and 14% of subjects gained ≥5% of baseline weight. Using estimated marginal means, weight gain was associated with worsening pain (mean 27.1 mm; 95% confidence interval [95% CI] -1.1, 55.2), stiffness (mean 18.4 mm; 95% CI 1.5, 35.3), and function (mean 99.3 mm; 95% CI 4.0, 194.6) compared to stable weight. Weight loss was associated with reduced pain (mean -22.4 mm; 95% CI -44.4, -0.3), stiffness (mean -15.3 mm; 95% CI -28.50, -2.0), and function (mean -73.2 mm; 95% CI -147.9, 1.3) compared to stable weight.
CONCLUSION: Weight gain was associated with adverse effects on knee symptoms, particularly in those who are obese and who have OA. Although losing weight is potentially beneficial for symptom improvement, the effects were more modest. Avoiding weight gain is important in managing knee symptoms.