Despite massive research efforts, it remains unclear how mechanical ankle instability (MAI) and functional ankle instability (FAI) affect joint control in the situation of ankle sprain.
Video of an acute ankle sprain – Djokovic
This case report from D. Gehring et al., describ when one athlete sprained his ankle while performing 3 different run-and-cut movement (45 degree turn, 180 degree turn and a -20 degrees turn).
A 3D kinematics, and muscle activity of the lower limb were recorded and compared to 16 previously performed trials.
Motion patterns of global pelvis orientation, hip flexion, and knee flexion in the sprain trail deviated from the reference trials already early in the preparatory phase before ground contact.
During ground contact, the ankle was rapidly plantar flexed (up to 1240°/s), inverted (up to 1290°/s) and internally rotated (up to 580°/s) reaching its maximum displacement within the first 150 ms after heel strike.
Rapid neuromuscular activation bursts of the m. tibialis anterior and the m. peroneus longus started 40–45 ms after ground contact and overshot the activation profile of the reference trials with peak activation at 62 ms and 74 ms respectively.
Therefore, it may be suggested that neuromuscular reflexes played an important role in joint control during the critical phase of excessive ankle displacement.
The purpose of this study was to evaluate whether individuals with MAI have deficits in stabilising their ankle joint in a close-to-injury situation compared with those with FAI and healthy controls.
Ankle-joint control was assessed by means of three-dimensional motion analysis and electromyography in participants with FAI and MAI (n=19), in participants with pure FAI (n=9) and in healthy controls (n=18). Close-to-injury situations were simulated during standing, walking and jumping by means of a custom-made tilt platform.
– increased ankle inversion in the injury mechanism
– increased risk for subsequent ankle sprains
– specific countermeasures are needed
Individuals with FAI and MAI displayed significantly greater maximum ankle inversion angles (+5°) and inversion velocities (+50°/s) in the walking and jumping conditions compared to those with pure FAI and controls. Furthermore, individuals in the FAI and MAI group showed a significantly decreased pre-activation of the peroneus longus muscle during jumping compared to those with FAI. No differences between groups were found for plantar flexion and internal rotation, or for muscle activities following tilting of the platform.
Conclusions The present study demonstrates that MAI is characterised by impairments of ankle-joint control in close-to-injury situations. This could make these individuals more prone to recurrent ankle sprains, and suggests the need for additional mechanical support such as braces or even surgery. In addition, the study highlights the fact that dynamic experimental test conditions in the acting participant are needed to further unravel the mystery of chronic ankle instability.
It is of special interest to understand how neuromuscular control mechanisms and mechanical constraints stabilize the ankle joint. Therefore, the aim of the present study was to determine how expecting ankle tilts and the application of an ankle brace influence ankle joint control when imitating the ankle sprain mechanism during walking.
Ankle kinematics and muscle activity were assessed in 17 healthy men. During gait rapid perturbations were applied using a trapdoor (tilting with 24° inversion and 15° plantarflexion). The subjects either knew that a perturbation would definitely occur (expected tilts) or there was only the possibility that a perturbation would occur (potential tilts). Both conditions were conducted with and without a semi-rigid ankle brace.
Expecting perturbations led to an increased ankle eversion at foot contact, which was mediated by an altered muscle preactivation pattern. Moreover, the maximal inversion angle (−7%) and velocity (−4%), as well as the reactive muscle response were significantly reduced when the perturbation was expected. While wearing an ankle brace did not influence muscle preactivation nor the ankle kinematics before ground contact, it significantly reduced the maximal ankle inversion angle (−14%) and velocity (−11%) as well as reactive neuromuscular responses.
The present findings reveal that expecting ankle inversion modifies neuromuscular joint control prior to landing.
Although such motor control strategies are weaker in their magnitude compared with braces, they seem to assist ankle joint stabilization in a close-to-injury situation.
Brace application & knowledge about upcoming ankle tilts can assist in reduction in injury-related ankle inversion.