Visual lameness exam detects subtle flaws

The visual lameness exam is the art of practical science when evaluating a performance horse.

As one component of the visual lameness exam, an associate of Dr. Juliet Hedge analyzes the horse's ability to perform the Walk-Trot-Walk-Trot method.

It is applied in highest form during the pre-purchase examination. It is a most powerful tool when examining for the more subtle lameness occurrences where a horse is not performing up to expectations or previous performance levels. In order to use this tool to determine the abnormal, it is imperative that the evaluator has a proficient grasp of the normal. Observation of many horses, at work, and at play, is the key to an effective visual lameness exam.

Once a normal standard has been established, the visual lameness exam can evaluate the horse against that standard. The exam should be performed in an organized, systematic manner.

Standing:

Begin the examination with the horse standing at rest on flat footing. This should be done in a quiet area that is familiar to the horse. Look for any abnormalities in standing position, signs of pain, foot resting or switching and localized swelling. A quick overview of the horse's conformation will establish potential problem areas. Visual assessment of the feet and hoof tester examination at this time will alert you to abnormalities of locomotion that may occur.

Walk Trot Walk Trot (WTWT):

Proceed to watch the horse moving in straight lines on a hard surface. I stand in a fixed position and have the horse walk directly away from me about 40 meters. The handler turns the horse in place and trots the horse directly at me. The horse is turned again and trotted away from me the same 40 meters. The horse is turned in the opposite direction and walked back directly at me (Photos 1 and 2).

Working on a hard surface allows me to listen to the sound of the hoof fall as well as watch it. A lighter sound on hoof landing may indicate a problem in that limb to be explored later. As the horse moves away, I can evaluate the freedom of movement of the hind limbs and quarters. Note any asymmetry of hip and sacral elevation. Head bobs are obvious from this position. Observe the straightness of hoof placement, tail position, asymmetrical body bend, deviations of gait and hock function. When moving toward me I again note any sign of head bobbing from the front limbs or head thrust from the hind limbs. Look for freedom of movement of the front limbs and shoulders, abnormal body bending off the straight line, straightness of hoof placement (winging in, winging out, rope walking) and alignment of flight path between front and rear limbs.

Lateral trot:

This exercise is also performed on the hard surface. I position myself approximately 10 meters up along the track. The horse trots by me, and I start to move with it for several strides as it passes. I do this from both sides (Photo 3).

A subtle lameness can sometimes reveal itself if you match the horse's front or rear leg action with your own. Observe the head and neck carriage from the side position, the roundness and strength of back, length and arc of foot stride, foot placement on landing (look for abnormalities of heel-toe action) and buckling or hyperextension of the fetlocks.

Positional locomotion:

Movement from the standing position allows evaluation of small muscle structures and neurological abnormalities. With the handler holding the head with one hand and the other hand on the girth area, the horse is turned 360 degrees in place several times in each direction. Body bend to each side and resistance is noted. The feet and legs are observed for appropriate crossover. While standing, each foot is manually cocked and timed until the horse corrects it to the supporting position. This requires proprioceptive awareness on the part of the horse. The horse is than backed up several steps. Monitor evenness of stride from side to side, resistance to backing, head and body position while backing for signs of discomfort or pain.

An associate has the horse trot by him and then starts to move with it for several strides as it passes. This part of the lameness exam evaluates the lateral trot.

The stifles are inspected for abnormalities. This a good time to palpate the muscles of the back, hips and hindquarters for muscle spasms, swelling, abnormalities or hypersensitivity. Myofascitis can usually be detected in this way.

Flexion tests:

Standard flexion tests of each leg and joint are performed and evaluated against the initial WTWT for changes in function. Each leg is held in the flexed position for one minute then the horse is trotted away in a straight line for six to eight strides. Excessive lameness following flexion will need to be further explored.

Longe line:

This exercise is performed on soft or working footing. The horse is longed in a 15-20 meter circle in each direction at the walk, trot and canter for several minutes (Photo 4).

Longing may be one of the most revealing aspects of the visual lameness exam. Whole body position can be evaluated at work as well as individual parts. Head bob or head thrust is clearly visible on the longe line indicating limb lameness.

For the longe line exercise, a horse is longed in a 15-20 meter circle in each direction at the walk, trot, and canter for several minutes.

The body position must be carefully observed for bend, shoulder in or out, haunches in or out, roundness of back, evenness of gait at the trot and canter. Is the horse comfortable at each gait or does it rush the gait in an unbalanced fashion? Stride length and quality are easily examined on the longe line. Abnormalities of any locomotion factors should be further explored and evaluated as primary issues versus secondary or compensatory issues in the process of identifying subtle lameness.

Hills and blindfolds:

This final exercise in the visual lameness exam is for evaluation of the joint and neurological function. A reasonably steep hill is used with dependable footing. Grass is preferred. With the examiner standing at the base of the hill, the horse is led up and down the hill at a walk. This is repeated at the trot. The horse is than blindfolded (a soft surgical towel works well). The exercise is repeated at the walk and trot with the blindfold in place.

This is a very revealing test for EPM infected horses. Few can walk up the hill with a blindfold on. Normal horses have no trouble negotiating hills with a blindfold on. Varying levels of neurological disease will show as resistance to moving with the blindfold, slow hypermetric front leg action especially coming downhill and great difficulty walking uphill without falling. Any non-neurological locomotion difficulties should be noted during this exercise with particular attention to limb joint function.

Integration of all parts of the visual lameness exam can identify problem areas and point the practitioner in the direction of further work. You must establish whether a single problem exists or if there are multiple contributing factors and whether the issues are primary or secondary. Comparison against an established normal standard allows the evaluator to determine whether the horse is guarding an area of the body while in motion, and/or overusing another area. Is the problem suspensory (the limbs) or structural (the vertebral column)? A thorough visual lameness examination takes time. The time expended will identify problem areas and prevent premature narrowing of focus in diagnoses and treatment.