Stair climb muscle power is associated with gait speed, sit-to-stand performance, patient-reported outcomes and objective measures of mechanical muscle function in individuals with knee osteoarthritis – secondary analysis from an RCT

Background: Mechanically measured leg extensor muscle power (LEP) predicts functional performance, patient-reported outcomes (PROMs) and mechanical muscle function in patients with knee osteoarthritis (OA). The stair climb test (SCT) have been used to assess LEP in clinical populations, but the relationship between SCT derived LEP and functional- and self-reported outcome measures in patients with knee-OA remains unknown. Objectives: To investigate the relationship between LEP derived from SCT, and patient-reported outcomes (PROMs), functional performance, knee extensor muscle strength (MVIC), rate of force development (RFD) and Nottingham LEP in individuals with knee-OA. Design: Cross-sectional study. Method: SCT power was obtained in 96 knee-OA patients (age 56.9 ± 7.7 yr. males n = 47, females n = 49). The dependent variable was SCT power, while independent variables included 4 × 10 m fast-paced walk (4x10m-FWT), sit-to-stand (STS), STS power, KOOS, Oxford Knee Score (OKS), LEP, MVIC, and RFD. Results: There were strong correlations (r = 0.72–0.80, p < 0.01) between SCT power and 4x10m-FWT and STS. There were weak-to-moderate correlations (r = 0.22–0.42, p < 0.05) between SCT power versus OKS and all KOOS subscales. Moderate correlations were observed between SCT power and Nottingham LEP, MVIC, and RFD (r = 0.53–0.64, p < 0.01). Conclusions: SCT power correlates positively with functional performance, PROMs and mechanical lower limb muscle function in male and female individuals with knee-OA.