Understanding the risk of intra-articular medication in racehorses

Intra-articular medication is widely used in the treatment of joint injury and joint disease in horses. Medications such as corticosteroids are very effective for treating soft tissue inflammation and reducing pain. However, in racehorses a high proportion of joint injury and joint disease results from damage to the subchondral bone due to the repeated loads generated on joint surfaces in galloping horses. Fortunately, fractures arising from the subchondral bone are relatively uncommon, however subchondral bone injuries that remain confined to the joint surface are very common. The inflammation and pain associated with such injuries can be managed with intra-articular medication, but these medications have no ability to reverse subchondral bone damage. Therefore medication potentially allows horses that have developed microdamage to continue to race and train exposing them to the risk of exacerbation of existing injuries. It has been found that racehorses undergoing local injection of corticosteroids suffer a higher rate of musculoskeletal injury for seven weeks post injection and the injury and fracture rate is higher following injection on multiple occasions. Clinicians have advocated radiographing joints prior to treatment to mitigate the risk of subsequent injury. While this approach has merit, radiographs are relatively insensitive for detecting subchondral bone injury. The use of advanced imaging will increase the detection of subchondral bone injury however no imaging method developed to date can detect microdamage so we are always ignorant to the level of subchondral bone injury at the time of treatment. It is therefore prudent to use intra-articular medication sparingly and to make sure owners and trainers are fully aware of the risks involved.

Chris Whitton

BVSc FANZVCS PhD Chris leads the Equine Limb Injury Prevention Program at the University of Melbourne Equine Centre a multidisciplinary research program funded by Racing Victoria, the Victorian State Government and the University of Melbourne, combining microstructural analysis, histopathology, biomechanics, epidemiology and mathematical modelling, dedicated to developing preventative training and management protocols for racehorses.

Chris trained as a specialist equine surgeon at the University of Sydney, Australia, gaining Fellowship of the Australian and New Zealand College of Veterinary Scientists in Equine Surgery by examination in 1995. He also completed a PhD in Carpal disease of racing horses at the University of Sydney in 1998 before moving to work at the Animal Health Trust in Newmarket, England in 1996. From 1999 to 2004 he ran his own surgical referral practice at the Newcastle Equine Centre in Australia and has worked at The University of Melbourne since 2004 as a Specialist surgeon and researcher.

He has published over 70 peer reviewed papers and contributed to 12 book chapters. He has been awarded over $13million in research grants. He regularly presents educational lectures on injury prevention to trainers in Australia and has also presented to trainers and racing veterinarians in England, Ireland, Wales, Hong Kong, Singapore, Korea, Brazil, and Uruguay.