Concurrent validity and reliability of clinical evaluation of the single leg squat

This study determined reliability and concurrent validity of measurements of the single leg squat made by novice examiners. Twelve video recordings of individuals performing a single leg squat were evaluated by six student physical therapists. Students assessed movement quality on an ordinal scale and manually measured frontal plane knee movement quantity on a video monitor. Inter- and intrarater reliability of ordinal scale ratings were determined via quadratically weighted kappa. Inter- and intrarater reliability of frontal plane knee measures were determined through intraclass correlation coefficient models 2,k and 3,k (k = 3 ratings), respectively. Concurrent validity of frontal plane knee measures was examined by comparison with Vicon-Peak motion-tracking system measures via Bland-Altman scatterplots. Ordinal scale measures displayed intrarater reliability ranging from 0.38 to 0.94 and interrater reliability of 0.68 (0.46-0.87). Intrarater reliability of frontal plane knee measures ranged from 0.88 to 0.98 and interrater reliability of 0.99 (0.97-1.00). Difference scores between student and computer-generated measures of frontal plane knee movement were significantly different as determined through Bland-Altman scatterplots and calculation of the upper and lower limits of agreement.