Symmetry of trunk and femoro-pelvic movement responses to single leg loading tests in asymptomatic females.

Single leg loading tests are used clinically to examine balance and loading strategies in individuals with lower limb pain. Interpretation of these tests is through pain responses and comparisons with the asymptomatic leg. The purpose of this study was to examine normal differences in trunk and pelvic movement between legs during the single leg stand, single leg squat, hip hitch and hip drop tests, and to compare observational and quantitative assessments of trunk movement during the single leg squat test. Thirty-one asymptomatic females (age = 21.7 ± 3.1 years) performed each test in a random sequence and quantitative analysis of coronal plane trunk lean (magnitude and direction), and femoro-pelvic angle was conducted using photographic image analysis. Within- and between-side minimal significant differences (MD) for femoro-pelvic angle were defined for each test. All tests had excellent within-side reliability (intra-class correlation coefficients (ICC) = 0.87-0.97, standard error of measurement (SEM) = 0.6-1.2°). The between-side MD for femoro-pelvic angle was 6.3, 6.5, 9.7, and 6.7° for the single leg stand, single leg squat, hip hitch and hip drop tests respectively. The magnitude of trunk lean was small, increased with test complexity and was not consistent in relation to the stance leg. Excellent agreement (87-93%) for the direction of trunk movement between observers, and between observational and quantitative analysis (80-96%) was established for the single leg squat test. The patterns of trunk motion, and thresholds for significant difference in femoro-pelvic angle established in this study, will assist the interpretation of single leg loading tests in individuals with lower limb pain disorders.