Oestrogen replacement combined with resistance exercise in older women with knee osteoarthritis: a randomised, double-blind, placebo-controlled clinical trial

Background Interventions targeting physical function decline in older women with knee osteoarthritis (KOA) are vital for healthy ageing. The additive benefits of combining oestrogen replacement therapy (ERT) with resistance exercise remain unclear. Objective To evaluate the additive effect of low-dose ERT on physical performance when combined with a muscle resistance exercise programme (MREP) in older women with KOA. Design This is a placebo-controlled, double-blind, randomised clinical trial. Subjects The subjects were community-dwelling women aged ≥65 years with chronic knee pain and KOA diagnosis. Methods Participants completed a 3-month MREP and were randomised to receive daily low-dose transdermal ERT (oestradiol 0.54 mg/day) or placebo. Outcomes were assessed at baseline, postintervention and 12 months later. The primary outcome was change in 30-second chair stand test (CS-30) score. Secondary outcomes included muscle mass, knee extension strength, walking performance, metabolic indicators, knee pain scale and 12-item short-form health survey (SF-12). Between-group differences in CS-30 changes were analysed using a linear regression model based on the intention-to-treat principle. Results Among 168 individuals screened, 75 participants (mean age 73.8 years, SD 5.8) were enrolled and randomised into an ERT group (n = 37) or a placebo group (n = 38). Baseline CS-30 scores were 14.81 (SD 3.95) in the ERT group and 15.58 (SD 3.48) in the placebo group. At 3 months, mean changes were 2.59 (SD 2.58) and 1.79 (SD 2.28) repetitions, respectively. The primary analysis showed no statistically significant between-group difference [regression coefficient: 0.81 (95% CI: −0.31, 1.92); P = .16]. Post hoc subgroup and sensitivity analyses suggested that benefits may exist among early-stage KOA participants. SF-12 mental health scores also improved significantly in the ERT group. No serious adverse events occurred. Conclusions ERT did not confer significant additive benefits to resistance exercise overall but may improve outcomes in early-stage KOA and mental health domains. These exploratory findings warrant further investigation.