Pua YH, Wrigley TW, Cowan SM, Bennell KL. Intrarater test-retest reliability of hip range of motion and hip muscle strength measurements in persons with hip osteoarthritis. Objective To examine the relative and absolute intrarater test-retest reliability of muscle strength and range of motion (ROM) measurements of the hip performed in people with hip osteoarthritis. Design Repeated measures. Setting Human movement laboratory of a university. Participants Participants (N=22; 10 men, 12 women; age range, 50-84y) with hip osteoarthritis. Interventions On 2 separate occasions, at least 1 week apart, isometric torque measurements were obtained from the hip rotators, flexors, abductors, and extensors. Passive ROMs in hip rotation, flexion, abduction, and extension were also determined. Main Outcome Measures Relative reliability was estimated using the intraclass correlation coefficient, model 2,2 (ICC2,2). Absolute reliability was estimated using the coefficient of variation (CV) and the standard error (SE) of measurement. Results For measurements of muscle strength, ICC2,2 ranged from .84 to .97, and the CV ranged from 8% to 15.7%. Hip extensors and internal and external rotators showed high ICC2,2 (>.96) and low CV (<9.8%); hip abductors showed the lowest ICC2,2 (.84) and the highest CV (15.7%). For ROM measurements, ICC2,2 ranged from .86 to .97 and SE ranged from 3.1° to 4.7°. Hip flexion ROM showed the highest ICC2,2 (.97) and an SE of 3.5°; hip extension ROM showed the lowest ICC2,2 (.86) and the highest SE (4.7°). Conclusions Strength and ROM testing of the hip in people with hip osteoarthritis can be performed with good to excellent reliability.