Equine Lameness Evaluation

Lameness is an indication of a structural or functional disorder, in one or more limbs or the spine, evident while the horse is standing or in movement. It can range from very mild discomfort, which may only be perceived by the owner or trainer as a decrease in level of performance, to severe pain in which the horse is unwilling to bear weight on the limb. As one of the most common and most expensive medical problems in horses, lameness represents a large concern to the equine industry as well as to individual horse owners.

When your horse presents to the veterinarian for lameness, we will often start with a thorough palpation of all four limbs and the spine, checking for heat, swelling, or pain on palpation. We will also check for increased fluid in each of the joints and tendon sheaths, which is referred to as effusion. A hoof tester exam is often done as well, checking for pain as pressure is applied to different regions of the sole.

Visual Examination

A visual exam is the next step of the lameness evaluation. The vast majority of lamenesses are easiest to perceive at the trot. The horse will often be evaluated while being trotted in hand on hard ground as well as in a circle, whether in hand or on the lunge line. Many lamenesses will manifest more strongly when evaluated in a circle. It is often helpful to watch the horse both on hard and soft ground, as the lameness may appear differently in these situations. Some horses with subtle lamenesses will also be evaluated at the canter, or while being ridden.

The nature of the visual exam is very subjective. In subtle lamenesses, it may be very difficult to tell which limb is the source of the pain, especially if multiple limbs are involved. Different veterinarians will focus on different aspects of the horse when watching a horse being trotted for lameness examination, but there are some commonalities. It is often helpful to look up at the motion of the torso and head of the horse rather than being distracted by the movement of the limbs themselves.

The majority of forelimb lamenesses are “impact” lamenesses, which means that the discomfort is occurring as the limb strikes the ground. A horse with impact lameness will not drop its head as low when this limb is on the ground as it does when the other limb is on the ground. Other forelimb lamenesses are “push-off” lamenesses, which means that the discomfort arises as the limb is pushing off the ground. A horse with push-off lameness will throw its head up as it pushes off the ground to help take the weight off the affected limb. In either case, what we perceive is the head being higher on the lame limb and lower on the sound limb (known as a “head nod”).

Subtle hindlimb lameness is often more difficult to visualize than is forelimb lameness. Many people stand behind the horse and watch the hips move on either side of the pelvis. On the side that is the source of the lameness, there will be more up and down movement of the hip. Other people watch the entire pelvis as a whole. In this case, the pelvis sinks less as the lame limb strikes the ground with an impact lameness, and rises less with a push-off lameness. Determining whether the left or right hind limb is affected is often the most difficult question to answer in the evaluation of a subtle lameness.

Because lameness evaluation by veterinary practitioners is subjective in nature, we grade the lameness on a scale from one to five in order to facilitate communication and understanding. If the lameness can only be seen intermittently at the trot, it is a grade one. If the lameness is consistently seen under certain circumstances (for example, it is visible every time the horse is circled to the right on hard ground), it is a grade two. A grade three lameness is visible consistently at the trot under all circumstances. If the lameness is visible at the walk, it is a grade four, and a grade five lameness is very severe, with the horse not bearing any weight on the limb in question. Although there are other grading scales in use, this one published by the American Association of Equine Practitioners (AAEP) is straightforward and is quite commonly used by equine veterinarians.