Abstract

A variety of mechanisms have been proposed as causes for Chronic Ankle Instability (CAI), including the delayed neuromuscular response of ankle evertors, a deficit in corticomotor excitability, or weakness of these muscles. Studies dealing with the strength evaluation of ankle evertors have classically been based on isokinetic tests and reported conflicting results. Not only is isokinetic evaluation not readily applicable in daily practice, it is also performed in open kinetic chain while ankle inversion sprain occur through a weight bearing closed kinetic chain mechanism. In this context, an alternative functional test has recently been proposed to assess the closed kinetic chain insufficiency of ankle evertors in CAI patients. This functional option assesses the ability of the ankle to resist an inversion challenge in weight bearing conditions, using a specific ankle inversion destabilisation device equipped with a gyroscope. Recent papers reported this test to primarily recruit ankle evertors under static and dynamic conditions, and highlighted promising findings regarding CAI subjects. They identified a link between the decrease of ankle joint stability and the insufficiency of the evertors in CAI subjects during an ankle inversion control performed by means of an eccentric recruitment of the evertors in full body weight conditions. This functional test also appeared more discriminant than an isokinetic eccentric assessment, potentially enabling a better identification of impairment in ankle evertors function in CAI. These recent findings support the hypothesis of a causative link between the decrease of ankle joint stability and the insufficiency of evertors, as assessed through functional testing. This suggests that an easy-to-apply functional test could be implemented in any clinical examination before and after the rehabilitation programme following an ankle sprain or in CAI patients. This test may also be utilised in prevention in order to monitor ankle evertors’ skills for longitudinal follow-up purposes in athletes.