Kinematics of rising from a chair: image-based analysis of the sagittal hip-spine movement pattern in elderly people who are healthy.

BACKGROUND Rehabilitation of elderly patients with sit-to-stand (STS) dysfunction includes retraining coordinated movement among participating body segments. Although trunk position is considered important, spinal movement has not been measured. OBJECTIVE The aim of this study was to describe the sagittal thoracolumbar kinematics and hip-lumbar interaction during the STS task in elderly people who were healthy in order to guide physical therapists in developing treatment strategies. DESIGN This was an observational study. METHODS Ten retroreflective markers were attached to the midline thoracolumbar spine, pelvis, and right lower limb of 41 elderly people who were healthy. A 2-dimensional video analysis system was used to measure sagittal thoracic, lumbar, hip, and knee joint angles during the STS task. Maximal available flexion-extension angles in these joints and regions also were determined. RESULTS Prior to buttocks lift-off, forward trunk lean comprised concurrent hip and lumbar flexion and thoracic extension. Hip flexion dominated, with a hip/lumbar ratio of 4.7:1 and a thoracic/lumbar ratio of 1.7:1. The hip and lumbar spine contributed 90% and 23% of their maximal available flexion angle, respectively, and the thoracic spine contributed 86% of its maximal extension range of movement. After lift-off, the hips and lumbar spine extended (ratio of 5.2:1), and the thoracic spine flexed (thoracic/lumbar ratio of 0.4:1). At lift-off, the hips and knees were similarly flexed (96 degrees ) and then locked together in a linear pattern of extension. Following lift-off, there was a brief transition phase (5% of STS duration) in which, although the hips, knees, and lumbar spine were extending, the trunk continued to flex forward a few degrees. LIMITATIONS Results may differ in elderly people who are less active. CONCLUSIONS The revised model for image-based analysis demonstrated concurrent hip and thoracolumbar movement during the STS task. Close to full available hip flexion and thoracic extension were needed for optimal STS performance.