Moderate vitamin D deficiency is associated with changes in knee and hip pain in older adults: a 5-year longitudinal study

Background: Vitamin D is important for bone, cartilage and muscle function but there are few studies on its association with joint pain. Objective: To investigate whether serum vitamin D predicts change in knee and hip pain in older adults. Methods: Longitudinal population-based cohort study of randomly selected older adults (n=769) aged 50-80 years (mean 62 years); 50 were male. Serum 25-hydroxyvitamin D (25-OHD) was assessed at baseline by radioimmunoassay, and pain at baseline, 2.6 and/or 5 years using the Western Ontario and McMaster University Osteoarthritis Index (WOMAC) questionnaire. We used linear regression with adjustment for age, sex, body mass index and season, then further adjusted for potential structural mechanisms (radiographic osteoarthritis, bone marrow lesions, chondral defects and muscle strength). Results: Mean total knee WOMAC score was 3.2 (range 0-39). 4.2 of participants had moderate vitamin D deficiency at baseline (25-OHD 12.5-25 nmol/l). 25-OHD