Towards a Better Understanding of the Biomechanics of the Equine Distal Limb

The equine distal limb and associated lameness problems will occupy a large propor- tion of a veterinary surgeon’s time, in particular, lameness problems of the digit and the fetlock joint. over the past 5-10 years, knowledge of the anatomy of the distal limb has advanced considerably with the development of advanced imaging techniques. During the same time, more advanced computing facilities, accelerometers and high speed video cameras have facilitated research relating to the biomechanics of the distal limb, the foot and the metacarpophalangeal joint (MCpJ), in particular. these advances have provided us with a better understanding of the movements of, and forces acting upon the distal limb. the technology has advanced to the point that the foot-ground interac- tion can be studied in the laboratory and in the horse’s normal working environment. the insights gained from these studies are beginning to inform our veterinary treat- ments as well as the design of the surfaces upon which horses perform. a better under- standing of the biomechanics of the distal limb will inform our understanding of the aetiology and therefore, the potential treatments of common lameness problems.

Functional anatomy
The anatomy of the equine digit is unique and has evolved to enable the horse to move quickly and efficiently. as we consider the different anatomic structures, their intimate interactions must be understood in order to understand how this relatively small struc- ture can function to support a large, rapidly applied load. one of the features that is unique to the equine digit is the arrangement of the laminae, in particular, the presence of secondary lamellae which increase the surface area of attachment between the bony column and the keratinised epidermal tissue of the hoof horn. in addition, the lamellar structure allows the third phalanx (p3) to remain within the hoof capsule when the loading of the limb pushes p3 distally. the digital cushion and collateral cartilages func- tion to dissipate the large newton loads that are experienced by the foot. the tensile pull of the DDft helps to counter the ground reaction force while storing elastic energy during stance to assist in propulsion forward at the point of break-over. overall, the hoof capsule and the internal structures are designed to absorb and dissipate a large portion of the load applied to the digit during equine locomotion. [...]