2026 Volume 53 Issue 1 Pages 44-48
Objective: This study aimed to evaluate the reproducibility and measurement error of Q-angle assessments performed using surface anatomical landmarks by calculating intra-class correlation coefficients (ICCs) and the minimal detectable change at the 95% confidence level (MDC95).
Methods: Ten healthy individuals without knee pathology were assessed bilaterally. Four physical therapists with 1, 5, 10, and 13 years of clinical experience each measured the Q-angle three times. Intra- and inter-rater ICCs and MDC95 values were calculated.
Results: The mean intra-rater ICC was 0.94±0.05, which indicates high consistency within raters. In contrast, the average inter-rater ICC was 0.34±0.02. Notably, the pair with 5 and 13 years of experience demonstrated a high inter-rater ICC of 0.92±0.02. Their corresponding MDC95 was 0.90±0.88°, while other rater combinations ranged from 3.00±0.46° to 7.09±3.59°.
Conclusion: High reproducibility of Q-angle measurements appears to require a measurement precision of ≤1°, which emphasizes the importance of accurate palpation of anatomical landmarks.
