Overground and walkway ambulation with unilateral hip osteoarthritis: comparison of step length asymmetries and reproducibility of treadmill mounted force plate readings.

The purpose of this study was to analyze and compare the degree of step length asymmetry of patients with hip osteoarthritis during free walking and treadmill ambulation and to determine the reproducibility of treadmill based vertical ground reaction force parameters. Twelve subjects with monoarticular hip osteoarthritis undergoing total hip replacement surgery were assessed preoperatively. The assessed parameters were step length, maximal forces at heel strike and push off minimum force, force inclining and declining rate and relative stance time. The results indicated significant step length differences when comparing overground and treadmill ambulation. The extent of step length asymmetry did not have a consistent expression in different gait conditions. The study demonstrated sufficient intraday reliability for mean GRF measurements. While comparing data from treadmill and walkway locomotion of patients with osteoarthritis it should be taken into account that the amount of step length asymmetry is not identical. Patients with gait disabilities seem to have a somewhat lower level of repeatability and it appears that an increased number of practice or acclimatization trials are necessary.