The ability of riders and trainers to recognise or acknowledge pain-related gait abnormalities in horses appears to be limited, says equine orthopaedics specialist Dr Sue Dyson.
Dyson, who is head of clinical orthopaedics with the Centre for Equine Studies at Britain’s Animal Health Trust, cites several studies in a just-published review that highlight shortcomings among owners and trainers in the recognition of these problems.
“There appears to be a perception among riders and trainers that horses can have ‘a lazy hind limb’, whereas in reality most of these horses are lame,” Dyson writes in the latest issue of Applied Animal Behaviour Science.
Dyson, who examines clinical issues around equine performance and the application of equine science in her review, cited a 2014 study of 506 sport horses in normal work that were perceived by their owners to be sound. However, 47% were assessed to have pain-related gait abnormalities. Some of these were apparent in-hand and in straight lines, but most were detected only when ridden.
In another study of 23 horses presumed sound by their owners, 14 showed fore-limb lameness in straight lines.
In yet another study, 57 dressage and showjumping horses in normal work and considered sound by their owners were then assessed in hand, after flexion tests, on the lunge on both soft and firm surfaces, and ridden. Only 14 were sound under all circumstances, with the rest showing some lameness.
“Riders and trainers are frequently unable or unwilling to recognise lameness or other behavioural changes that are a manifestation of pain,” Dyson writes.
She acknowledges that recognising low-grade lameness can be challenging, but says there are many clues which veterinarians, riders and trainers should recognise with careful observation.
Dyson says there also appears to be a lack of recognition of some behavioural signs of pain such as evasive action when approached with tack, putting the ears back, and biting or kicking while being tacked up. Ridden signs include an open mouth, ears back, an unwillingness to go forward, spookiness and resistance.
Work discipline, body size and conformation may be risk factors for lameness, and work surfaces may also have a role.
Dyson says saddle fit for both horse and rider is crucial for good thoracolumbar health and function. “The tendency of a saddle to persistently slip to one side is most commonly secondary to hind limb lameness.”
She highlights concerning evidence around saddle fit identified in several studies, noting that even riders are more likely to have back pain exacerbated by using an ill-fitting saddle.
Dyson points to several studies that examined the short-term effect of the rider on biomechanical function in horses. There is, she says, little doubt that rider balance, body-weight and ability, as well as their effectiveness in riding a horse forward with good balance, all potentially had a short-term influence on horses’ performance and a longer-term effect on musculoskeletal health.
She cites a 2014 study involving 104 sports horses in which a link was found between larger rider body-weights and the presence of minor left or right asymmetries of the thoracolumbar region.
Dyson acknowledges the challenges around detecting the presence of pain in horses, particularly if an objective assessment is required. “Although a number of techniques have been developed for the objective assessment of gait, even with the development of wireless inertial measurement units, there are currently some limitations in data interpretation in horses presenting with poor performance rather than overt lameness.”
She continues: “Since we know that some horses only manifest overt lameness when ridden, but may show adaptations to pain-related lameness on the lunge, how can we judge a horse to be sound unless it is evaluated when ridden?
“Historically, ridden exercise has not been routinely used as part of a lameness assessment, but this is now considered to be essential for sports horses unless the horse is too lame to assess ridden.
“There are,” she says, “many lamenesses that are only apparent in a ridden horse, so assessment in hand and on the lunge is only part of the whole picture.
“Horses may appear completely normal if allowed to work in a ‘novice outline’, but when asked to collect, the horse may look very different, because greater biomechanical demands are being placed on the musculoskeletal system, particularly the thoracolumbosacral regions and hind limbs.
“Likewise, a horse may appear relatively normal when trotting around the periphery of an arena, but if asked to trot in 10-metre circles or in figures-of-eight (sequential 10-metre diameter circles to the left and right) the picture may be very different.”
Dyson says it should be borne in mind that the inside fore limb and hind limb transcribe a circle about 1 metre smaller in radius than the outside hind limb.
She traverses a range of size and conformation factors that studies suggest may play a role in lameness. For example, in one study, dressage horses measuring 170cm or more at the wither had a 15% greater chance of lameness compared with those standing 163cm or less. Certain bodyweight-to-height ratios appear to increase the risk of foot pain, while a study involving Dutch warmbloods found that taller horses had a shorter competitive life than smaller horses.
Work surfaces certainly have an influence, she says. “Ground that was uniform in normal and hot and/or dry conditions was associated with decreased risk of lameness.
“Slipping, tripping or sudden loss of balance were associated with an increased lameness risk.
“Wax-coated and sand and rubber surfaces were better than sand, sand-and-PVC, woodchips or grass,” she says, citing a 2010 study. “Woodchips led to increased risk of slipping compared with other surfaces, whereas sand led to increased risk of tripping.
“Privately owned arenas were potentially safer than commercially owned multi-use arenas, which highlighted the importance of arena maintenance.”
Depending on discipline, different surfaces may pose different risks for injury. She cites a study of elite showjumping horses, in which training and competing on grass was identified as a risk factor for days off from training. In contrast, sand with wood sawdust was protective.
She says there is currently minimal scientific information about training regimes in sports horses, and limited knowledge around over-training and repetitive over-use injuries in horses.
Early recognition of musculoskeletal problems is a potential key to successful management, she suggests.
Horses and riders vary in their natural abilities to perform, she says. “There is also a huge spectrum of the aspirations of riders and what they wish to achieve with their horses. However, whatever the circumstances, optimisation of the horse-saddle-rider interaction is crucial for both equine performance and equine welfare.”
Dyson says that while technology can be used to help educate riders through science-based observations, we must not lose sight of reading behavioural cues, which can tell us a lot about a horse’s welfare.
“There are still wide gaps in our knowledge about strategies to minimise the risks of injuries to the ridden horse, and a need for further research making use of technological advances in the fields of equine biomechanics with the results applied in equitation science.”
Equine performance and equitation science: clinical issues
The abstract can be read here.