Association of pain and fatigue with health related quality of life in people with osteoarthritis.

Osteoarthritis (OA) is a major contributor to years lived with disability among musculoskeletal conditions, with its prevalence rising due to aging populations and increasing obesity rates. Total knee (TKA) and hip (THA) arthroplasty are common surgical interventions aimed at restoring function and improving quality of life (QoL). However, the relative contributions of sociodemographic and clinical factors to overall OoL remain insufficiently understood. This study examined the associations between pain and fatigue with the physical component summary (PCS) and mental component summary (MCS) of QoL, while controlling for functional status and sociodemographic variables. The sample consisted of 423 patients with knee OA (n = 241, mean age 65.1 ± 8 years, 40.2% male) and hip OA (n = 182, mean age 63.5 ± 10 years, 60.9% male). Correlations, multiple linear regressions, and mediation analyses were used to analyse the data. For PCS, total explained variance was 44% in TKA and 40% in THA. FS was significantly associated with PCS in both groups, with a stronger association in TKA (β = -.60, p < .001). Pain was the most significant contributor to PCS in THA patients (β = -.42, p < .001) but was not significantly related to PCS in TKA (β = -.03). For MCS, total explained variances were lower (18% in TKA and 22% in THA), with fatigue emerging as the strongest contributor in both groups (β = -.42 knee OA; β = -.48, hip OA, p < .001). Fatigue fully mediated the relationship between pain and MCS, accounting for nearly 80% of the effect. No mediation effect was observed for PCS in THA, and only partial mediation (8.4%) was found in TKA. These findings underscore the need for tailored interventions to enhance post-arthroplasty recovery and QoL improvement. Pain management should be prioritized for hip OA to improve physical well-being, whereas comprehensive, long-term strategies targeting fatigue may be may be essential for mitigating mental health burdens in both OA groups.