Longitudinal associations between adiposity and change in knee pain: Tasmanian older adult cohort study.

Objective: The aim of this study was to describe the longitudinal relationship between adiposity and change in knee pain.

Methods: A total of 1099 participants aged 50-79 were randomly selected from the local community in Southern Tasmania, of which 767 were followed up on average 5.1 years later. Knee pain was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) at each time point. Consistent knee pain was defined as knee pain at all three time-points. The five pain subscales were grouped into weight-bearing pain and non-weight-bearing pain according to the nature of pain. Body fat and lean mass were assessed using dual energy x-ray absorptiometry (DXA).

Results: Baseline body mass index (BMI) and body fat mass were deleteriously associated with consistent knee pain over follow-up. BMI was consistently associated with increases in weight-bearing and non-weight-bearing pain. Fat mass was associated with an increase in non-weight-bearing pain. In mixed-model analyses, WOMAC total pain score was associated with BMI (β = 1.27) and body fat mass (β = 1.17). The association of lean mass was not significant after adjustment for fat mass.

Conclusion: BMI is the most consistent correlate of knee pain in older adults. Fat mass is associated with non-weight-bearing knee pain suggesting systemic mechanisms are involved.