When is it time to quit?

The repetitive, cyclical nature of loads on the musculoskeletal system associated with training for and competition in equine athletic pursuits results in a relatively high incidence of fatigue-related injuries and degenerative conditions in competition and race horses. The incidence and rate of onset of disease is related to the magnitude of load each cycle, which is determined by the speed and nature of activity, together with intrinsic (animal-related) and extrinsic (environment-related) factors. The ability to tolerate training and competition with minimal damage to musculoskeletal tissues does, in part, appear to be animal-dependent although the mechanisms behind such variation is not yet understood.

Common examples of repetitive stress injuries (RSI) in the racehorse include stress fractures and disease of subchondral bone and whole joints. There is some evidence that injuries to the superficial digital flexor tendon are also a manifestation of RSI.

The consequences of RSI are accumulative and there is often a point where associated pathology becomes irreversible. Furthermore, focal pathology associated with RSI of the skeleton is a significant risk factor for more serious injuries, such as complete fracture of long bones.

Anti-inflammatory and analgesic drugs are regularly used to manage the impact of RSIs in sports horses. While this may be reasonable practice there is a danger that on occasions it masks the severity of underlying pathology, thereby increasing the risk that disease progresses to a state where it becomes irreversible or where pathology that risks acute, catastrophic injury goes undetected.

Clinicians have a responsibility to act as guardians of the horse. They should understand the pathobiology behind musculoskeletal disease that is common in competition horses, appreciate the significance of administering medications that mask the severity of disease and be prepared to acknowledge when risk of continuing training, under the influence of medication, is against the best interests of the horse.

Dr Chris RIGGS

BVSc, PhD, DEO, DipECVS, FRCVS

Chris studied Veterinary Science at the University of Bristol, UK, in the early nineteen eighties. He received further training in Equine Surgery at the Royal Veterinary College, UK and was awarded a PhD for research into the causes of racehorse fractures in 1991. He subsequently worked as a Senior Lecturer at the Philip Leverhulme Equine Hospital, University of Liverpool, where he developed specialist skills in equine surgery. He gained further clinical experience at several equine referral centres in the United Kingdom and Australia before joining the Hong Kong Jockey Club as Head of Veterinary Clinical Services in 2003. He was appointed to a new role in the Club as Director, HKJC Equine Welfare Research Foundation/ Chief Advisor, Mainland Veterinary Engagement in 2019.

Chris has a particular interest, and specialist qualifications, in surgery and orthopaedics. He has published over 80 scientific papers about fatigue damage in bone and its role in racehorse fractures, among other topics. He also cares deeply about helping to provide opportunities for young colleagues to further their clinical skills, with a focus on Mainland China.

Chris is a Fellow of the Royal College of Veterinary Surgeons, UK and holds positions as Adjunct Professor at the College of Veterinary Medicine and Life Sciences, City University, Hong Kong, Special Professor at the School of Veterinary Medicine and Science, University of Nottingham, UK, and Guest Professor at Inner Mongolia Agricultural University