31 Mar Diagnosing Equine Lameness

Lameness in the horse is manifest in many forms. It can be severe or subtle, consistent or inconsistent, acute or chronic, and easy or very frustrating to resolve.

If you notice lameness in your horse, the first step in deciding what to do involves making an objective assessment of the situation. A horse that is head-nodding lame, quite reluctant to move, and has severe swelling is likely to need same-day attention. A horse that has been missing his left lead or pinning his ears when asked to trot is a less urgent case and can be evaluated within a few weeks. When scheduling your lameness exam, please make sure that someone will be available to trot, longe, and/or ride the horse. Please do not have the shoes pulled before we come as it is important for us to see the horse “as is.” Of course, if a clip is stuck in the sole, having a farrier pull the shoe is a good idea.

A lameness exam has many components. A quick initial look at the horse’s gait as he is moved from stall or pasture may reveal the affected leg. If not, the horse is walked or trotted on the end of a lead and/or longe line. The veterinarian looks for a head nod, hip hike, asymmetrical stride, dragging toe, and a number of other more subtle hints to confirm which limb is bothering the horse most. Once that’s decided, the sore limb is palpated and compared to the normal limb. Heat, swelling, or bounding pulses may narrow the site of the problem to a particular joint or tendon.

Hoof testers are also used to further pinpoint the problem. These tools are like large pliers that are used to put pressure on the sole or frog and the hoof wall. Pressure is applied on all parts of the hoof, and the veterinarian observes if the horse flinches or pulls his leg away.

If this test yields little result, the vet performs flexion tests. The fetlock (ankle), carpus (knee), and tarsus (hock) are joints routinely examined in this way. The joint is held in its most flexed position for 45 to 90 seconds. The horse is then immediately trotted off.

A change in his way of going leads the veterinarian to further assessment. It is more difficult to perform flexion tests on the elbow, shoulder, stifle, and hip joints. Fortunately, most lameness occurs in the horse’s
lower limbs!

As the location of the problem becomes more defined, perineural (around a nerve) and/or intra-articular (into a joint) blocks are used. Carbocaine, a solution similar to Novocaine used at the dentist’s office, is injected to numb a particular area of the limb. After several minutes, the vet watches the horse move again. If the lameness is no longer evident or not as severe, the painful area has been numbed. Because certain nerves supply only certain parts of the body, the veterinarian can use that information to start deciding on specific areas that need imaging.

If a bone problem such as arthritis or a fracture is suspected, a radiograph (x-ray) is the most logical imaging modality. If the soft tissues of the limb (i.e., tendons and ligaments) are in question, the ultrasound is a better choice. These procedures can often be done on site at a farm. The ultrasound can be interpreted immediately, as the image is projected onto a screen while the vet is scanning the suspect area. Radiographs can be taken at a farm, but need to be processed chemically back at the clinic. Optimally, when multiple areas need to be radiographed, it is best to have them done at a clinic. This gives the vet the opportunity to make the “prettiest” pictures!

Imaging is a wonderful asset but does not always give a definitive answer. Occasionally nuclear scintigraphy is recommended. This is more commonly referred to as a bone scan. A material that can be detected by a gamma camera is injected into the horse’s jugular vein; after a specified time, the horse stands in front of the gamma camera, and “hot spots” are identified. The closest clinic that can perform equine bone scans is Cornell. Cornell is also able to do CAT scans on certain parts of the limb.

Obviously, scheduling lameness exams is difficult. Before the initial exam is conducted, it is hard to predict how many nerve blocks will be required. Encountering an uncooperative patient can also add time to the procedures. Unfortunately, few lameness issues are resolved in a single visit; a second or third appointment may be required. A referral to another clinic is also a possibility. Anything more complicated than a simple sole abscess can begin to rack up the costs. If you hope to track down and solve your horse’s problem, you need to plan on spending a fair amount of time and money on your lame friend.