Lameness is one of the most common problems that occur in the horse and that owners will have to address. Many owners have experienced lameness and the examination process, but there are various ways to approach the lameness examination procedure. There are also new advanced diagnostic tools to help identify the limb or limbs that are causing the lameness and allow objective quantification of improvement when the region of the limb in questions is isolated to the source of pain.
Basic Lameness Evaluation
Veterinarians commonly have to rely on the owner, trainer or the rider’s information and history about the horse to help narrow down the cause of the lameness. Therefore, an accurate history about the horses’ age, career, level of work, previous treatments, abnormal things that the horse is doing under saddle or refusing to do while working are all important information that is gathered before the exam begins. This information can be the key to understanding or honing in on the cause of the lameness. In some cases, the cause of poor performance, refusing to work as hard, or refusing certain tasks can be unrelated to a musculoskeletal injury.
Physical examination of the horse is generally a good starting point before the horse is put through the lameness examination. Palpation of the limbs, ligaments, tendons and joints can give clues to potential problem areas that can be leading to horses’ lameness issues. Palpation of the neck, back and sacral regions can give clues if the horse is muscle sore, back sore and/or has old injuries that can lead to soundness issues. Hoof testers are an important part to a complete physical examination because of the propensity of forelimb lameness to arise from the feet. Lastly, visual examination for conformation, shoeing or trimming methods and comparison of musculoskeletal symmetry of the horse are all part of a complete examination.
The initial lameness examination is typically completed while trotting the horse in hand in a doctor preferred pattern over a hard or firm surface to evaluate the horses’ movement. This portion of the exam in typically referred to as a baseline evaluation before flexions are performed. A grading system is used set by the American Association of Equine Practitioners (AAEP) to have a standardized method to grade degrees of lameness. The system is a 0-5 scale and has a defined criterion that the horse has to meet in order to be selected for a grade. Then specific areas of the limbs are isolated and stressed by performing flexion tests. This is a technique to induce temporary stress on the joint(s) to discern if pain is arising from that particular joint(s) or area of the limb and the degree of response to the flexion is noted. Some veterinarians grade the response numerically or by a verbal descriptor scale, for example, mild, moderate or severe.
More difficult or less obvious lameness cases require putting the horse under different circumstances to exacerbate the lameness. Other circumstances the horse can be put under to achieve this are lunging the horse, riding the horse under saddle or having a rider perform the specific gait or movements that the horse is exhibiting lameness under or poor performance.
Diagnostic Nerve and Joint Blocks
Just because a limb has been found to be the source of lameness doesn’t mean much unless the specific cause can be diagnosed. Diagnostic nerve blocks are used routinely in equine lameness examines to further narrow down the area since horses can’t tell us where the pain is coming from. Therefore, after blocking the horse one zone at a time the horse will show improvement once the site the pain is arising from is blocked out. Diagnostic blocks can be performed by injection local anesthetic drugs perinueral (adjacent to specific nerves) to block pain sensation or sterilely into a joint to desensitize the joint. Once the anesthetic drug is injected around the nerves or into the joint it only takes minutes to block the pain sensation from that region allowing repeat examination of the horse to see if the source of lameness has been identified.
Lameness has long been a subjective measure of a horses’ gait that can have its pitfalls. If you want to test this theory, just try to get a group of people to agree on where a horse is lame, and you will quickly find out it is difficult to get everyone to be on the same page. Luckily there are ways now to objectively quantify a horse’s gait/lameness with a system developed by veterinarians and engineers to give real data about how a horse moves. The system can pick out which leg is lame and also indicate if there is an improvement in the lameness after diagnostic anesthesia is performed. This can be all done simply with a tablet in the veterinarians hand and inertia sensors placed on the horse. The sensors collect the information as the horse is being trotted in hand or with a rider on the horse. The information is sent wirelessly to the tablet and the software calculates and grafts the information in real time.
Read more in the January issue of Oklahoma Farm & Ranch.