Reliability and concurrent validity of 30-s and 5-time sit-to-stand tests in older adults with knee osteoarthritis.

Introduction: Sit-to-stand (STS) movement is fundamental in daily life. STS tasks have been used to assess lower limb muscle strength, balance control, and functional abilities in various populations, but limited information is available on their use in older individuals with knee osteoarthritis.

Objective: We here examined the intra-rater, inter-rater, and test-retest reliability of the 30-s and 5-time STS tests, and calculated the standard error of measurement (SEM) and minimal detectable change (MDC). Moreover, we explored the concurrent validity of these tests by analysing their correlation with knee muscle strength, pain, stiffness, and physical function in older adults with knee osteoarthritis.

Method: This cross-sectional study included 60 older participants diagnosed with knee osteoarthritis. Baseline demographic information and data on pain, stiffness, and physical function using the modified Western Ontario and McMaster Universities Osteoarthritis (WOMAC) were obtained. Participants performed the 30-s and 5-time STS tests as well as knee muscle strength assessment using a hand-held dynamometer. After 1 week, 30 participants were reassessed to evaluate test-retest reliability.

Results: The 30-s and 5-time STS tests had excellent intra-, inter-, and test-retest reliability (intraclass correlation coefficients: 0.990-1.000, 0.996-0.999, and 0.841-0.853, respectively) with a large SEM and MDC. Both STS tests significantly correlated with knee extensor and flexor strength and all modified WOMAC domains (Pearson's correlation coefficients: 0.28-0.61, p < 0.05).

Conclusion: The 30-s and 5-time STS tests are reliable assessment tools and correlate with knee muscle strength, pain, stiffness, and physical function in older adults with knee osteoarthritis. Key Points • The 30-s and 5-time STS test can serve as surrogate measures in various aspects of knee health, including muscle strength, pain levels, stiffness, and overall physical function, in older adults with knee osteoarthritis. • Both these STS tests are dependable tools, accessible for both experienced and inexperienced assessors to administer effectively.