The Effects of Ankle Bracing and Direction on Knee Angles During Single-Leg Hop Tasks

Abstract

Bracing is commonly used for support and stabilization of the ankle during physical activity. As bracing is intended to minimize ankle movement, transient effects at the knee are not always considered and may increase injury risk due to improper joint mechanics. PURPOSE:To assess the effects of ankle bracing techniques (ABT) on knee angles during the landing phase of single-leg hop (SLH) tasks. METHODS:15 subjects were recruited (21.9±1.7 years, 1.78±.27m, 70.0±17.1kg) and were free from any previous traumatic lower body injuries. Reflective markers were applied to the participants’ lower extremities and trunk, and tasks were captured using a 3-D motion analysis system. For each participant, an initial control session was performed in a non-braced condition for the SLH tasks. For the subsequent three sessions, an ABT was applied (white tape, lace-up brace, and kinesio-tape). The type of ABT used during each session was counterbalanced between participants. Each session, participants performed a SLH task from five different starting positions, all within 70 cm from the target landing zone. Peak knee angles (°) were measured for all joint rotations during the landing phase. A multivariate analysis of variation (MANOVA) was performed to examine the main and interaction effects of ABT and SLH direction. An alpha level was set at .05 a priori, with Tukey’s HSD performed post hoc to discern differences if significance was found. RESULTS: MANOVA results exhibited no significant differences for the main effect of ABT (p>.05), but significant differences were demonstrated for the main effect of SLH direction (p=.001). Minimal knee flexion demonstrated significant differences for the lateral (-22.5±6.4°) compared to anterior (-18.7±4.9 °;p=.004), anteromedial (-18.9±5.6°;p=.006) and medial (-19.5±6.5°;p=.004) directions of the SLH. Maximal external knee rotation displayed significant differences for the lateral (-0.2±5.3°) compared to the medial (-3.0±6.1°;p=.035) SLH direction. CONCLUSIONS: The results indicate that ankle bracing does not significantly alter joint mechanics at the knee, whereas SLH direction does have an effect on knee angles during the landing-phase. When considering the prevention and probability of knee injuries, attention to the direction of the movement performed is an important factor.