Application of an extended information-motivation-behavioral skills model to predict HPV vaccine acceptability among Chinese gay, bisexual, and other men who have sex with men.

Knee osteoarthritis (KOA) is a degenerative condition of the knee joint characterized by the progressive loss of articular cartilage, leading to pain, stiffness, and mobility limitations (). Globally, KOA affects more than 650 million people, with prevalence increasing markedly with age (). Beyond pain and joint degeneration, KOA impairs lower-limb biomechanics through muscle weakness, reduced neuromuscular control, and joint instability, leading to progressive functional decline. Among daily tasks, stair negotiation is particularly challenging for individuals with KOA, as it requires greater knee range of motion, strength, and balance than level walking. Difficulty with stairs is an early, disabling limitation associated with poorer quality of life (, ). Consequently, stair-climbing performance directly reflects deficits in strength, balance, and pain tolerance, making it a clinically meaningful indicator of overall functional status (). To assess physical function in people with hip or knee osteoarthritis, the Osteoarthritis Research Society International (OARSI) recommends several performance-based tests to complement patient‑reported outcome measures, including the Timed Stair Test (TST) for stair negotiation (). Together with the Chair Stand Test and the 40‑m Fast‑Paced Walk Test (FPWT), the TST forms part of the minimal core set recommended for both clinical and research use, underscoring the critical need for objective assessments of stair‑climbing ability. Traditional TST protocols typically require ascending and descending 4–5 steps and have been widely used in older adults and individuals with hip or knee osteoarthritis (, ). These tests are limited by their simplified task components, which may not adequately reflect the biomechanical complexity of stair negotiation encountered in daily life. To address this limitation, a more comprehensive version of the TST was developed that integrates multiple functional components, including rising from a chair, ascending and descending stairs, level walking, and returning to a seated position, performed with or without an external load. Previous studies have demonstrated adequate to excellent psychometric properties of the comprehensive TST in some populations. Specifically, the TST showed adequate reliability in individuals with obesity (intraclass correlation coefficient [ICC] = 0.88) (), and excellent intra‑rater reliability (ICC = 0.985–0.991) along with acceptable concurrent validity among stroke survivors (). Furthermore, stair‑focused performance tests have demonstrated good to excellent test–retest reliability (ICC = 0.83–0.95) and adequate validity in individuals with KOA (–), displaying strong associations with FPWT performance, quadriceps strength, balance measures, and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores (). Despite this evidence, a critical gap remains regarding the comprehensive TST’s psychometric properties in individuals with KOA. Specifically, its reliability, validity, and discriminative ability under both unloaded and loaded conditions – which accurately reflect the physical demands of real‑world stair negotiation, such as carrying groceries – remain unclear. Addressing this gap is essential to establish the comprehensive TST as a robust and clinically meaningful assessment tool. Therefore, this study aimed to: () compare TST performance between participants with KOA and healthy older adults; () assess the intra‑rater, inter‑rater, and test–retest reliability of TST completion times under both loaded and unloaded conditions; () examine concurrent validity with knee‑related functional assessments; and () determine the optimal TST cut‑off values for differentiating stair‑climbing performance.