Sore shins or, bucked shins occur when young racehorses (usually 2 year olds or unworked racehorses) are over trained. A diagnosis is made by palpation of the front of the cannon bone where heat and pain are evident however, the racehorse is not always lame. Further confirmation can be made by taking an X-ray of the cannon bone which will often show periosteal new bone formation over the front of the cannon bone.
The latest evidence from research suggests that sore shins occur due to high-strain cyclic fatigue, as a result of excessive compression causing tiny cracks in the cannon bone. The bone responds by laying down new layers of bone where it is most stressed (periosteal new bone formation). As a result the periosteum (the fibrous membrane of connective tissue that covers bone) becomes lifted, inflamed and painful.
Under an appropriate training programme the cannon bone has time to remodel and strengthen allowing the racehorse to cope with the stresses and strains of subsequent galloping/training sessions. However, when the racehorse is galloped in a weakened state (due to a lack of adequate recovery time) the cannon bone(s) will continue to react by laying down new layers of bone, further lifting the periosteum and cause considerable pain for the racehorse. If prolonged galloping continues at this stage further cracking in the cannon bone will occur which could ultimately lead to a fatal fracture of the cannon bone.
Sore shins are avoidable by adapting the training programme of young racehorses. The accepted approach is to gallop young racehorses over shorter distances (1-2 furlongs, 2-3 times per week) rather than over longer distances of prolonged galloping. This reduces the compressive forces exerted on the front of the cannon bone and thus reduces the ‘damage’ in that area. This, followed by adequate rest allows the cannon bones (and the rest of the skeleton for that matter) to rebuild and strengthen and allow the racehorse to continue training and progress through the season. In the event of a young racehorse developing sore shins they should be removed from regular training and given time to heal (this could be anything from 6 weeks to 4 months, depending on the severity). When they return to training they are galloped over shorter distances to ascertain what they can handle and their training programme is progressed from that benchmark.
Invasive treatment options are available such as shockwave therapy, various forms of blistering, periosteal scraping and pin firing or freeze firing for example. There is a lot of debate over the effectiveness and morality of some of these treatment options. We haven’t used any of the above to date as we believe the least invasive management of sore shins is best. This consists of early detection, rest, cold hosing, the application of topical anti-inflammatory preparations, non-steroidal anti-inflammatory drugs (if needed) and adapted training for example.
For an owner, having your racehorse removed from training and racing can be a frustrating period of time. However, sore shins are just one of many conditions that a trainer has to be aware of and understand in order to keep your racehorse on the track throughout the season. Early detection through daily examination combined with appropriate treatment and training techniques much reduce the chance of sore shins and other musculoskeletal conditions occurring. We make every effort to avoid musculoskeletal complaints such as sore shins developing however, completely avoiding sore shins in all young racehorses is difficult indeed.