Gender specific validity and Reliability of 2 minutes step test in patients with different grades of knee Osteoarthritis

Knee osteoarthritis (OA) is a chronic, progressively developing disorder that causes pain, reduced mobility, and diminished functional ability. Performance-based outcome measures are essential for objectively evaluating functional limitations. The Two-Minute Step Test (2MST) is a simple, cost-effective alternative to walking-based tests such as the Two-Minute Walk Test (2MWT); however, its psychometric properties across genders and disease severity remain inadequately explored. To assess test-retest consistency, absolute reliability, and concurrent validity of the 2MST compared to the 2MWT in people with OA in their knees.
Methodology: A cross-sectional study with 208 knee OA patients was conducted. Functional capacity was assessed using the 2MST and 2MWT under standardized conditions. Test-retest reliability was evaluated using Cronbach's alpha and the Intraclass Correlation Coefficient (ICC). Coefficient of Variation (CV%), Smallest Worthwhile Change (SWC), Minimal Detectable Change (MDC95), and Standard Error of Measurement (SEM) were used to assess absolute Reliability. Concurrent validity was assessed using Spearman’s correlation coefficient (r). Findings demonstrated excellent (ICC = 0.972; 95% CI: 0.918–0.963; Cronbach’s α = 0.986). Gender-specific analysis revealed high reliability in both males (ICC = 0.929; α = 0.963) and females (ICC = 0.952; α = 0.975). However, grade-specific reliability was moderate (Grade 2: ICC = 0.477; Grade 3: ICC = 0.495). Absolute reliability analysis showed MDC₉₅ = 16.46, SEM = 5.94, SWC = 3.76, and CV% = 25.44. 2MST and 2MWT showed a small but statistically significant positive correlation (r = 0.223, p < 0.05). Subgroup analysis demonstrated a moderate significant correlation in males (r = 0.354, p < 0.05), while correlations in females (r = 0.037, p > 0.05) and across OA grades (Grade 2: r = 0.144; Grade 3: r = 0.126) were non-significant.
The 2MST is a reliable and useful tool for evaluating functional ability in people with osteoarthritis of the knee. Despite exhibiting outstanding reliability, its concurrent validity with 2MWT is limited, particularly across disease severity and in female participants.