Lower Extremity Biomechanics and Chronic Ankle Instability

Lateral ankle sprains (LAS) are the most common injury in active individuals. LAS often result in a condition known as chronic ankle instability (CAI). CAI is characterized by subjective feelings of instability and dysfunction within the individual. This includes muscle weakness and activation changes, range of motion and arthrokinematic alterations, proprioceptive and joint position sense changes and balance and postural control alterations. These deficits are hypothesized to play a role in the kinematics and kinetics during gait and jumping tasks in CAI patients. Previous studies have identified increased inversion and plantar flexion during gait and greater frontal plane motion during gait. Recently, novel statistical and non-linear techniques have been hypothesized to improve the analysis of the lower extremity biomechanics. The focus of manuscript one was to assess kinematics, kinetics and ground reaction forces (GRF) during walking and jogging gait between CAI and healthy controls using statistical parametric mapping (SPM). We found that CAI patients had greater ankle inversion during walking and jogging gait and greater eversion joint moments during jogging. No differences were found at the knee and hip. The purpose of manuscript two was to assess the impact of 4 weeks of comprehensive, progressive rehabilitation on lower extremity joint coupling in CAI patients. Rehabilitation including strength, balance and range of motion exercises is the standard of care for treating CAI patients. Rehabilitation has shown improvements in strength, balance and subjective function. We found that it also decreased variability between motion of the knee to the ankle and hip to the ankle during walking gait. The goal of manuscript 3 was to assess lower extremity joint coupling during a drop-vertical jump (DVJ) between patients with and without CAI. We found that CAI patients had higher variability, lower joint coupling magnitude and higher vector direction. These deviate from previous findings during gait and may represent the task constraint of DVJ on the sensorimotor function of CAI patients. CAI is an internal constraint that alters the lower extremity biomechanics during gait and DVJ. These changes may indicate an unhealthy motor control strategy that predisposes this population to instability and joint damage. Rehabilitation changes the joint coupling variability and may represent a protective organismic adaptation to create a stable joint.