Accuracy and Stability of Crossing Motion in Older Adults: With Focus on the Knee Joint

Abstract

Background: Accidental falls are caused by sudden perturbations, and thus, quick and well-organized stepping responses are needed. Stepping is one of the most important motions for avoiding falls in elderly patients. We sought to analyze foot motion during the volitional steps of older adults and compare it with that of younger adults. Methods: Eighteen healthy older adults (age: 70.8 ± 3.2 years) and 22 younger adults (age: 20.2 ± 0.3 years) were included in this study. The subjects crossed over a lateral obstacle 10 times, keeping the motion as consistent as possible. An infrared reflective marker, placed on the subjects’ heels, recorded motion through a three-dimensional motion analysis system. A clinical sensory test for knee proprioception was performed and the difference between the target and the actual angle of the subjects was calculated using an electrical goniometer. Results: The results of the motion analysis indicated that the trajectories of the heels in older adults were not consistent compared with that of young adults (p< 0.05). Unfortunately, the clinical sensory test and the time-series analysis of knee angle change were unable to detect a decline in the proprioceptive function of the knee. Conclusion: We believe that knee flexor muscles lack coordination in terms of eccentric contractions. This decline of coordination could cause the descending period to extend, which is the time from the top of the trajectory of the heel to the finish of the normalized motion. We also believe that the change in motion may indicate compensatory mechanisms for aging. This information can be useful for designing fall prevention exercises for the elderly population.