Neuromotor control of the lower limb in Achilles tendinopathy: implications for foot orthotic therapy

Achilles tendinopathy (AT) is a common injury in running sports. While the exact aetiology of Achilles injury is still unclear, foot orthoses are often effectively employed in the conservative management of the condition. Foot orthoses have traditionally been provided for people with AT on the basis that they may reduce the rearfoot eversion associated with excessive foot pronation. This increased rearfoot motion is thought to produce excessive Achilles tendon loads. To date, the available literature indicates that foot orthoses have small and unsystematic effects on rearfoot kinematics. However, limitations of foot kinematic measurement currently restrict the ability to conduct truly valid investigations into kinematic responses to foot orthoses. Therefore, the roles of alternate mechanisms, for which orthoses may provide clinical success in pathology such as AT, are now being investigated. One alternative theory is that foot orthoses alter neuromotor recruitment patterns and thus lower limb loads in response to the additional sensory input provided by the device. In AT, altered neuromotor recruitment patterns of the triceps surae have been hypothesized to create differential intratendinous loads. This may lead to pathological changes within the tendon. Furthermore, it is possible that foot orthoses may aid to normalize intratendinous loads via altering neuromotor activity in the triceps surae in AT. This review examines the literature with regard to changes in neuromotor recruitment as an associated aetiological factor in AT and the role foot orthoses may play in the management of this condition.