Balance Recovers Slowly Over Repeated Knee Crutch Exposure

The hands-free knee crutch is a contemporary assistive mobility device that has been shown to alter postural control upon first use but affords a more natural bipedal stance. However, the literature is scarce regarding balance after repeated exposure to this device. PURPOSE: The main goal of this study is to identify how balance changes during repeated use of the knee crutch. METHODS: Eleven healthy, college-aged participants completed balance testing with the knee crutch over the course of 5 weeks. Static and dynamic balance testing were conducted using a force plate. Static testing was performed by standing with eyes closed and minimal movement. Dynamic testing was performed with the participants maximally swaying in all directions without losing contact with the force plate. Week 1 included baseline (no crutch; BL) balance testing, crutch fitting with self-selected time for familiarization, and balance testing (with knee crutch; C0). Weeks 1-4 included a refamiliarization period followed by balance testing (with knee crutch; C1-4). Separate paired t-tests were used to determine differences between BL and C0, and C0 and C4, for each static and dynamic scores. Trend analysis was used to determine the best fit regression of static and dynamic scores over C0-C4 timepoints, separately. RESULTS: Static pathlength increased from 24.9 ± 2.0 cm at BL to 58 ± 6.2 cm at C0, indicating more sway during static stance (p < 0.001). Dynamic balance area reduced from 368.9 ± 26.6 cm2 at BL to 192.1 ± 17.8 cm2 at C0 (p < 0.001). Repeated use of the knee crutch (C0 v C4) did not significantly change the static balance pathlength. However, the dynamic balance area significantly increased after repeat visits from 192.1 ± 17.8 cm2 at C0 to 238.2 ± 30.9 cm2 at C4 (p < 0.05), without returning to BL values. Quadratic trends were found to be most correlated for both the static and dynamic scores (r2 = 0.8113 and r2 = 0.9529, respectively). CONCLUSIONS: The knee crutch causes a reduction in postural control. After repeated exposure, static balance followed a nonlinear recovery without significant improvement and dynamic balance showed significant recovery towards baseline. These findings highlight that static and dynamic sway are regulated by different mechanisms and improve knowledge of balance with knee crutch devices.