Hip and knee flexion of lead and trail limbs during ascent of a step of different heights by normal adults

ObjectiveTo describe and compare hip and knee flexion of the lead and trail limbs during step ascent.DesignDescriptive observational study.SettingUniversity research laboratory.ParticipantsFourteen healthy subjects.Main outcome measuresA seven-camera tracking system captured the kinematics of the lead and trail limbs as subjects ascended 20.3-cm and 40.6-cm steps, leading with each lower limb. Maximum hip and knee flexion were recorded bilaterally.ResultsDuring ascent of the 20.3-cm step, mean flexion was 66.3° for the lead hips and 20.6° for the trail hips [mean difference 45.7°, 95% confidence interval (CI) 43.5° to 48.0°]. During ascent of the 40.6-cm step, mean flexion was 92.5° for the lead hips and 26.8° for the trail hips (mean difference 65.6°, 95% CI 62.1° to 69.1°). During ascent of the 20.3-cm step, mean flexion was 90.5° for the lead knees and 57.6° for the trail knees (mean difference 32.9°, 95% CI 29.3° to 36.5°). During ascent of the 40.6-cm step, mean flexion was 119.9° for the lead knees and 73.2° for the trail knees (mean difference 46.7°, 95% CI 41.9° to 51.5°). A general linear model revealed that for both the hip and the knee, flexion was significantly greater in the lead limb than in the trail limb, and during ascent of the 40.6-cm step compared with the 20.3-cm step.ConclusionsThe hip and knee flexion used to ascend a step depends on whether a limb is leading or trailing, and on step height. For individuals with limited flexion in a limb, range demands will be reduced if the restricted limb trails during a step-to-step pattern.