Feeling the Strain

Many horse owners will be familiar with the feeling of dread when their horse damaged a tendon or ligament. Helen Triggs spoke to Professor Roger

W. K. Smith MA VetMB PhD

DEO FHEA DipECVSMR DipECVS FRCVS, Professor of Equine Orthopaedics at the Royal Veterinary College, to get an insight into scientific advances in equine tendon research that are leading to new treatments that could help horses in the future.

Tendon and ligament injuries are common in dressage horses, particularly as the level of training increases in intensity and the horse also increases in age. Scientific research is a continuous process to try and find ways of returning the horse to healthy work and has certainly moved on a lot in the last few decades.

Pictured

Right Inset: Steady rehab including walk exercise is important.

Below: Early diagnosis of a tendon injury can be key to successful treatment.

Prevention is obviously the best policy and it’s important to try and minimise injury as there is no magic bullet which will reverse damage. While tendons and ligaments can repair, they are usually less efficient than before the injury and more prone to re-injury.

“While injury can be a sudden event, occurring during exercise or in the field, there is a lot of evidence now that there is an accumulation of micro-damage in the tendon over time caused by high intensity exercise. We are constantly trying to identify the key processes and increase our understanding of why injuries occur which helps to develop preventative strategies,” says Professor Smith.

Understanding Why Injuries Occur

“Traumatic lesions look very different to overstrain injuries. The latter increase with age which is why we think there is a degenerative phase not normally seen in the young horse,” he points out.

Cellular senescence (deterioration) is being extensively researched in the human field. Senescent cells play a role in preventing the accumulation of procarcinogenic mutations. However, as they age, they lose the capacity to replace themselves and in turn become a source of inflammation. This can happen in multiple locations. Stephanie Dakin, Associate Professor of Skeletal Science at the University of Oxford has taken her work on the role of inflammation in equine tendonopathy into the human health field. Her research has identified a commonality between cell senescence and inflammation and the aging of tendon.

Professor Smith’s group believes that senescent cells may play a key role in this process. “Equine drugs that could inhibit this are currently under investigation,” he says. “Potentially inhibitory molecules could be administered into the site to prevent cells becoming senescent.”

Chavaunne Thorpe, lecturer in Basic Sciences at RVC, is developing our understanding of how tendon fibres slide in relation to one another which is crucial to understanding how they function and the impact of aging. The tissue between the tendon fibres that allows this sliding changes with age and so is probably the main site on which to focus our new treatments.

Progress In Diagnosis

Early diagnosis can be critical in identifying the scale of the injury and implementing a recovery regime.

“Ultrasound is the diagnostic workhorse and there are some newer techniques which allow us to identify injuries earlier and detect them where we couldn’t before. This is a combination of an improvement in the machinery and the quality of the images we get back,” comments Professor Smith.

Doppler imaging, which is used to track the movement of blood through the human heart, has been transposed into tracking blood in damaged tendons as it gives a read out of the degree of inflammation.

“We now have different ways of scanning injuries we couldn’t see before.”

In the US, vets are introducing PET (positron emission tomography) as a diagnostic tool for tendon injuries in the feet. However, with a cost of approximately $650,000 per machine, this is not yet available in the UK.

Non-invasive assessment is an interesting area of exploration. By measuring the height and degree of extension of the fetlock and elasticity of the soft tissue, the effect of injury and healing can be better determined. >

Success After Injury

Even with the current state of treatments, dressage horses have returned to the highest level of competition after injury.

Mr President was the partGelderlander that brought Steph Croxford to prominence in the dressage world. She trained him to Grand Prix and despite being a non-traditional dressage-type, the pair were being considered for team selection for the Beijing Olympics when he suffered a forelimb suspensory injury. “He took a misstep in the warmup at the show in Mechelen but went on to complete two tests. He was being given a topto-toe evaluation by team vet John McEwen who found he was reactive to the palpation of the suspensory ligament,“ recalls Steph.

“It took a year of road-walking under saddle – it was felt the slip and slide of walking would help with the realignment of the tissue.” After two years of rehab, Mr President returned to the ring and despite further tendon and collateral ligament injuries, plus a fractured pedal bone, he competed at international Grand Prix level for a further five years. When he retired at 18, Mr President was sound.

Alice Oppenheimer’s ride, Headmore Difinnity, has come back from the ligament coming away from the bone of a hind fetlock in 2019 to carry on his international Grand Prix career. Finn had just made his debut at Grand Prix when he injured himself in the field. “It was a major soft tissue injury so we rushed him to Rossdales Vets and the prognosis was guarded,” explains Alice. “Rachel Murray provided the most detailed rehab plan and this was key to his recovery. He had three courses of laser treatment but in the main it was down to the stable exercises, pole work and hours and hours of hand walking to get him strong. We had to do enough to get the fibres healing but not too much to cause injury.”

Controlled exercise was key to the recovery of Katrina Hall’s 22-yearold King of the Street when he tore his annular ligament nearly two years ago. A structured in-hand walking programme over eight weeks followed by a controlled ridden programme meant that he was able to continue his career at Advanced Medium. “It was a long haul but worth every second,” said Katrina.