Muscle function, quality and relative mass are associated with knee pain trajectory over 10.7 years

Periarticular muscle plays an important role in the pathogenesis of musculoskeletal pain. Werecently reported that pain population consists of distinct subgroups of which the causes andmechanisms may differ. This study aimed to examine the association of lean mass, musclestrength and quality with 10.7-year pain trajectory. 947 participants from a population-basedcohort study were analysed. Dual-energy X-ray absorptiometry was used to assess lean andfat mass. Leg, knee extensor strength and lower-limb muscle quality weremeasured/calculated. Knee pain was assessed by the Western Ontario and McMaster Universities Osteoarthritis Index pain questionnaire. Radiographic knee osteoarthritis (ROA)was assessed by X-ray. Three distinct pain trajectories were identified: “Minimal pain” (53%),“Mild pain” (34%) and “Moderate pain” (13%). Higher total and lower-limb lean mass wereassociated with an increased risk of “Mild pain” and “Moderate pain” trajectories relative tothe “Minimal pain” trajectory group, but these associations became non-significant afterfurther adjustment for fat mass. Total lean mass percentage was associated with a lower riskof “Mild pain” [relative risk ratio (RRR): 0.95, 95%CI 0.92-0.98] and “Moderate pain”trajectory (RRR:0.92, 95%CI 0.87-0.96). Greater leg and knee extensor strength and musclequality were associated with “Mild pain” and “Moderate pain” trajectories (RRR:0.52-0.65,all P