Biomechanics is “The science that examines the forces acting on or within a biological structure and the effects produced by such forces. ” ~Hay, 1973
However equine biomechanics is generally used to mean the study of equine movement and the equine musculo-skeletal system, ignoring most of the field. It is becoming widespread, and “experts” are springing up all over.
Motion capture systems are now available which will allow the performance horse to have “optimised” shoeing, examining the before and after effects of any changes. So far these have been used intelligently, but they are not sophisticated enough to distinguish between primary and secondary deviations – cause and compensation – and so it would be easy to overlook the effects of trying to change joint angles.
The equine distal limb joints are shock absorbers, particularly the fetlock (metacarpo-phalangeal joint). It flexes in proportion to the vertical ground reaction force of the limb loading (McGuigan and Wilson, 2003). Changes to the distal joint angles affect strain in the deep digital flexor tendon, the superficial digital flexor tendon and the suspensory ligaments (Lawson et al., 2007a), common sites of injury in the horse. Changes in hoof medio-lateral balance and width affects strain in the collateral ligaments (Lawson et al., 2008). Changes in shoeing affect both tendon and ligament strains (Lawson et al., 2007b) and inter-articular pressure in the distal interphalangeal (coffin) joint (Viitanen et al., 2003). For example an elevated heel increases distal interphalangeal joint pressure, increases superficial digital flexor tendon strain, unloads (and therefore shortens) the deep digital flexor tendon, and yet is often employed in showjumpers “to help the hock”.
Some gait analysis systems now are being marketed as easy enough for any vet or farrier to use. Let’s hope that they come with a lot of training and promote rather than discredit the field.