Association of body composition and physical activity with pain and function in knee osteoarthritis patients: a cross-sectional study

Abstract

ObjectiveThe objective of this study is to delineate disparities between patients with knee osteoarthritis (KOA) based on obesity status, investigate the interplay among body composition, physical activity and knee pain/function in patients with KOA and conduct subgroup analyses focusing on those with KOA and obesity.DesignCross-sectional study.SettingResidents of eight communities in Shijiazhuang, Hebei Province, China, were surveyed from March 2021 to November 2021.Participants178 patients with symptomatic KOA aged 40 years or older were included.Main outcomes and measuresThe primary outcome measure was knee pain, assessed using the Western Ontario and McMaster Universities Osteoarthritis Index-pain (WOMAC-P) scale. Secondary outcome measures included function, evaluated through the WOMAC-function (WOMAC-F) scale and the Five-Time-Sit-to-Stand Test (FTSST). Data analysis involved t-tests, Wilcoxon rank-sum tests, χ2tests, linear and logistical regression analysis.ResultsParticipants (n=178) were 41–80 years of age (median: 65, P25–P75: 58–70), and 82% were female. Obese patients (n=103) had worse knee pain and self-reported function (p<0.05). In general patients with KOA, body fat mass was positively associated with bilateral knee pain (β=1.21 (95% CI 0.03 to 0.15)), WOMAC-P scores (β=0.25 (95% CI 0.23 to 1.22)), WOMAC-F scores (β=0.28 (95% CI 0.35 to 1.29)) and FTSST (β=0.19 (95% CI 0.03 to 0.42)), moderate-intensity to low-intensity physical activity was negatively associated with bilateral knee pain (β=−0.80 (95% CI −0.10 to –0.01)) and Skeletal Muscle Index (SMI) was negatively associated with WOMAC-F scores (β=−0.16 (95% CI −0.66 to –0.03)). In patients with KOA and obesity, SMI was negatively associated with FTSST (β=−0.30 (95% CI −3.94 to –0.00)).ConclusionPatients with KOA and obesity had worse knee pain and self-reported function compared with non-obese patients. Greater fat mass, lower muscle mass and lower moderate-intensity to low-intensity physical activity were associated with increased knee pain and poor self-reported function. More skeletal muscle mass was associated with the improvement of objective function.