Measurement of function in hip osteoarthritis: developing a standardized approach for physical performance measures.

Assessment of physical function is regarded as an essential component to determining outcome in patients with hip osteoarthritis (OA). The Western Ontario and McMaster Universities Osteoarthritis Index physical function subscale (WOMAC-PF) has been recommended as the leading self-report measure to assess function in OA trials. However, recent evidence has questioned the construct validity and longitudinal validity of the WOMAC-PF for assessing physical function. In this perspective, we recommend that both self-report measures and physical performance measures of physical function are needed for a more comprehensive assessment of function in patients with hip OA. We propose the development of a standardized battery of physical performance outcome measures to complement self-report measures when capturing the construct of function in patients with hip OA.