Poor performance or lameness with no obvious cause may call for an examination known as a work-up. Gil Riley MRCVS explains.
A lameness work-up is an investigation of the horse’s movement to diagnose injury or damage that is causing pain.
The more accurate the diagnosis, the more finely-tuned the resulting treatment plan can be. This in turn maximises the likelihood of a successful outcome and a return to athletic work in the shortest possible period of time.
A work-up may be performed because a reason for lameness is not apparent, or because performance is below par.
There are many causes of loss of performance, including gastric ulcers, respiratory issues and temperament problems. By far the most common problem is orthopaedic pain, an abnormality somewhere in the musculoskeletal system.
The aim of the work-up is to determine the root of this pain, using a sequential series of steps.
A safe setting
With so many unavoidable variables due to the individuality of every horse, it is important to standardise the procedure wherever possible.
A work-up is ideally performed at the clinic, where the vet will be familiar with how horses respond to the environment, the handlers and the facilities. These facilities will have been designed to allow the most obvious demonstration of lameness in the safest way – a small gravel lunging ring, for example, that enables the horse to be seen moving on a hard surface with minimal risk of slipping.
Typically, one vet will use their experience and the examination results to lead them to the source of pain. Lameness clinicians tend to be quite obsessive about their craft, however, so a vet will often join in while a colleague is performing a work-up and make their opinion heard.
Bringing a horse to the clinic may therefore result in a speedier diagnosis. In certain cases, variations to the procedure may be necessary.
An unshod horse would not be lunged on a hard surface, to avoid making him footsore, while the riding part would be omitted, of course, for an unbroken or miniature horse.
If the answer is found with the initial, static examination, or on the straight-line trot, the process ends there. It would be inappropriate to put the horse through unnecessary discomfort that would provide no further information.
If a horse will not tolerate nerve-blocking injections, we may opt to introduce imaging earlier than usual to minimise distress caused. This is not ideal, as it will take more time to reach the correct diagnosis, but it is a better alternative to risking injury to the horse, vet or handler.
Unravelling issues
Lameness in the limbs is most common, but pain in other areas can result in poor performance – especially back issues, such as impingement of the dorsal spinous processes (kissing spines) or spondylosis of the vertebrae.
Such horses often exhibit no lameness on the straight-line trot or on the lunge, but show profound discomfort during ridden exercise under the weight of tack and rider. They may also resent palpation of the back, alerting the vet to the possibility of a problem in this area.
A work-up can also help to unravel a primary source of pain from secondary complications or compensatory lameness. An example would be hind limb suspensory pain – a common cause of lameness in dressage and event horses.
Because it can develop insidiously, and in both limbs simultaneously, the rider may not realise anything is wrong in the early stages. The horse may adapt his movement to minimise pressure on the painful suspensories by moving his pelvis more, causing sacroiliac pain. When his suspensory ligaments are blocked out (numbed), the clinic rider is
likely to report that he now moves more freely – but with a stiffness “higher up”. A subsequent nerve block of the sacroiliac area will then lead to further improvement.
Pain relief, such as phenylbutazone, should not be given for at least two days before the exam. Anything that makes lameness less obvious will make obtaining an accurate diagnosis more difficult.
What’s the verdict?
Eliminating possibilities to reach the correct diagnosis can take money and time. While a definitive diagnosis is obtained in most cases, some may still evade an absolute answer – although a logical and well-supported suggestion can usually be made.
Lamenesses that remain undiagnosed are usually suspected as being neurological in origin, emanating from the spinal cord or the associated spinal nerves and plexuses.
The emergence of gait analysis systems has been an exciting development in lameness investigation, particularly for horses that are unbroken or have become unrideable, or where lameness is so subtle that it is difficult for the vet to identify.
These systems, however, should be regarded as another tool available to the vet, and just part of the process in uncovering the source of some lamenesses.