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Lameness and Poor Performance in the Sport Horse: Eventing

Reprinted from aaep.org


by Sue Dyson, FRCVS


Eventing (horse trials) combines dressage, show jumping, and cross-country, together with steeplechase and roads and tracks phases in a long format three-day event. The event horse must primarily be a brave, clever, bold jumper cross-country, with scope and speed. However, in modern day competition this is not sufficient to excel, and the horse must also have reasonably athletic paces and a temperament that can be trained for dressage, combined ideally with an ability to show jump with care. Horses with a predominance of Thoroughbred breeding excel. The majority of pure warmblood horses struggle to achieve the speeds required at top levels, and, if always working in top gear, are more prone to injury.


Three-day eventing places extreme demands on the musculoskeletal system, through the efforts of both the training program and the competition itself. The horses compete on extremely variable terrain and must be able to cope with both hard and soft footing, often uphill, downhill, and across hills, and must be prepared accordingly. Galloping and jumping on various gradients place huge strains on the limbs and back, and horses with poor conformation are particularly at risk to injury.


Eventing is less forgiving than dressage or show jumping in this respect. Dressage in horse trials is almost always performed on grass and subtle gait abnormalities may be highlighted, especially when the ground is hard. Horses with poor foot conformation, upright hoof pastern axes, are back-at-the-knee or have straight hocks do not stand up well to top-level competition. The event horse is also much more at risk to develop lameness due to direct trauma than horses in either show jumping or dressage, particularly in the cross-country phase.


Horses usually reach advanced level by approximately 8 years of age and the majority of horses competing internationally are older. Most injuries in these horses are repetitive strain injuries to soft tissues or joints or the result of direct trauma, whereas in younger horses there is a broader range of lameness causes common to horses used in a variety of disciplines. Exertional rhabdomyolysis (tying up) occurs quite commonly and is most often recognized in recognized either in the cross-country phase or 10-minute break after the second roads and tracks phase, before the cross-country phase of a long format three-day event. The speed at which horses must perform, combined with jumping, results in a high incidence of strain of the superficial digital flexor tendons. This is probably also a cumulative injury reflecting frequency of competition and the speed at which the horse competes.


LOSS OF PERFORMANCE AND LAMENESS

Low-grade musculoskeletal problems may present as unlevelness in the dressage phase, especially when performing medium or extended trot, 10 meter diameter circles or lateral work. In show jumping, the horse may show any of the problems seen in the elite show jumper. In cross-country, the horse may be reluctant to jump drop fences or to gallop down hill.


It must also always be remembered that refusing may reflect lack of confidence of the horse or rider. A horse may compete very successfully at intermediate level but not have the confidence or scope to compete at advanced level. Horses that are too careful and try to avoid hitting fences may paradoxically not be brave enough for advanced level competition.


CLINICAL EXAM

A comprehensive clinical examination at rest is essential. The horse should always be assessed as a whole, not as a limb in isolation.


Particular attention should be paid to:

-Foot conformation, trimming and shoeing, and shoe wear -Joint flexibility, resistance to limb flexion and rotation, and pain -Fluid swelling in the joints, especially in the fetlock and pastern -Neck and back flexibility and muscle tension -Size, shape and reaction to palpation of the superficial digital flexor tendons and the suspensory ligaments


The horse should be examined standing squarely on a hard surface to detect muscle wasting, which may reflect a chronic low-grade lameness. It should be assessed moving in hand, before and after flexion tests, on the lunge on both soft and hard surfaces, and ideally ridden, since frequently horses have several low-grade problems when presenting with reduced performance which will only become apparent if the horse is examined under a variety of circumstances. Nerve blocking is essential to unravel the entire picture.

Significant inflammation of the superficial digital flexor tendon may be present without lameness and with minimal detectable clinical signs. Many riders apply a proprietary clay and bandage the limbs after fast work or competitions and this can suppress soft tissue swelling or mask localized heat. Whenever there is the slightest suspicion of injury the tendons should be examined ultrasonographically.


COMMON CAUSES

As described in the article, common causes of acute onset lameness in the event horse include:

- Inflammation of a suspensory ligament - Injury to a suspensory branch - Inflammation to a superficial digital flexor tendon - Exertional rhabdomyolysis (tying up) - Stifle trauma, including bruising, fracture of the patella or tibia - Foot soreness, trimming and shoeing problems - Over-reach - Traumatic arthritis of the fetlock and pastern joints - Degenerative joint disease of the hock - Inflammation of the digital flexor tendon sheath - Back and sacroiliac joint region pain


It is vital to have the horse examined by a veterinarian at the earliest sign of a problem, whether lameness, resistance or the onset of heat or swelling, so that appropriate treatment may be instituted to prolong the performance life of the horse.

Reviewed by original author in 2016.


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