Introduction. Total leg muscle function in hip OA patients is not well studied. We used a test-retest protocol to evaluate the reproducibility of single- and multi-joint peak muscle torque and rapid torque development in a group of 40–65 yr old hip patients. Both peak torque and torque development are outcome measures associated with functional performance during activities of daily living. Material and Methods. Patients: Twenty patients (age 55.5±3.3, BMI 27.6±4.8) who underwent total hip arthroplasty participated in this study. Reliability: We used the intra-class correlation (ICC) and within subject coefficients of variation (CVws) to evaluate reliability. Agreement: Relative Bland-Altman 95% limits of agreements (LOA) and smallest detectable difference (SDD) were calculated and used for evaluation of measurement accuracy. Parameters: Maximal muscle strength (peak torque, Nm) and rate of torque development (Nm•sec-1) for affected (AF) and non-affected (NA) side were measured during unilateral knee extension-flexion (seated), hip extension-flexion, and hip adduction-abduction (standing), respectively. Contractile RTD100, 200, peak was derived as the average slope of the torque-time curve (torque/time) at 0–100, 0–200 and 0 peak relative to onset of contraction. Protocol: After 5 min level walking at self-selected and maximum speeds each muscle group was tested using 1–2 sub-maximal contraction efforts followed by 3 maximal contractions 4s duration. Statistics: The variance components were estimated using STATA12, with muscle function and occasion as independent variable and patients as random factor, using the restricted maximum likelihood method (=0.05). Results. For all exercises and sides, the ICC's for peak torque were good (0.81–0.96) with CVws ranging from 5.0–10.8%. Similar good ICC's were observed for RTD200 on the non-affected side (0.83–0.93), whereas most exercises (4/6) on the affected side showed moderate to good ICC (0.72–0.82). We found moderate CVws for RTD200 with 12.8–18.7% and 10.3–18.9%, affected and non-affected, respectively. With few exceptions the ICC's and CVws for RTD100 were moderate to poor on the affected side but good to moderate on the non-affected side. The SDD's for peak torque ranged from 14.9 Nm to 39.0 Nm, equal to relative LOA of 13.9–23.8%. For RTD200, the SDD's were 77–257 Nm•sec-1 and 29.2–86.2%, absolute and relative, respectively. With few exceptions interventions measuring RTD100 and RTDpeak would have to find changes exceeding 60% for them to be statistical significant. Conclusions. Our novel set-up for lower limb
