Do self-efficacy, body mass index, duration of onset and pain intensity determine performance on selected physical tasks in individuals with unilateral knee osteoarthritis?

Purpose To investigate the contributions of Pain Self-Efficacy (PSE), Function Self-Efficacy (FSE), Body Mass Index (BMI), duration of onset of Knee OsteoArthritis (KOA) and Present Pain Intensity (PPI) to performance on Stair Task Test (STT), Timed Up-and-Go (TUG) and 20-Meter Walk Test (20-MWT) and explore correlations among the variables in individuals with unilateral KOA. Methods Participants were 51 (22 male, 29 female) consecutively-selected patients with unilateral KOA. Participants' self-efficacy (PSE, FSE), and PPI were assessed using Arthritis Self-Efficacy Scale and Box Numerical pain scale respectively. Participants' performance on STT, TUG and 20-MWT was also assessed. Data were analyzed with Pearson product moment correlation and Stepwise linear regression at alpha level of 0.05. Results Participants' mean age, duration of KOA onset and BMI were 52.18 ± 10.69 years, 30.29 ± 29.03months and 26.06 ± 3.86 kg/m² respectively. Participants' scores on 20MWT, TUG and STT had significant direct correlations with each other and with PPI while PPI had significant indirect correlations with PSE (r = −0.59) and FSE (r = −0.56). PSE had significant direct correlation (r = 0.65) with FSE. Both PSE and FSE had significant but low inverse correlations with scores on the performance tests. PPI explained about 43% or more of the variance in 20-MWT, TUG and STT. PPI and onset of KOA explained 62% of variance in 20-MWT while PPI and BMI jointly explained 60% of variance in TUG. Conclusion Though PSE and FSE significantly correlated with scores on the performance tests, PPI, duration of OA and BMI were the significant determinants of performance.