Equine Lameness Examination
Stress, strain or injury can take a toll on any horse, even one with no obvious conformation defects. When lameness occurs, you should contact your veterinarian promptly. A prompt examination can save you time, money and frustration by diagnosing and treating the problem immediately, possibly preventing further damage. The goal of such early examinations is to keep small problems from becoming big ones.
Traditionally, lameness has been defined as any alteration of the horse’s gait. In addition, lameness can be manifest in such ways as a change in attitude or performance. These abnormalities can be caused by pain in the neck, withers, shoulders, back, loin, hips, legs or feet. Identifying the source of the problem is essential to proper treatment.
AAEP LAMENESS SCALE
Most veterinarians will follow a predefined scale for lameness which is called the AAEP lameness scale. This scale helps us all to better communicate what we are seeing visually, Because each horse has unique performance characteristics, evaluating lameness can be challenging. Experienced riders may detect minor alterations in gait before they are apparent to an observer. Lameness may appear as a subtle shortening of the stride, or the condition may be so severe that the horse will not bear weight on the affected limb.
The scale ranges from zero to five, with zero being no perceptible lameness, and five being most extreme. The AAEP guidelines explain the grading system this way:
0: Lameness not perceptible under any circumstances.
1: Lameness is difficult to observe and is not consistently apparent, regardless of circumstances (e.g. under saddle, circling, inclines, hard surface, etc.).
2: Lameness is difficult to observe at a walk or when trotting in a straight line but consistently apparent under certain circumstances (e.g. weight-carrying, circling, inclines, hard surface, etc.).
3: Lameness is consistently observable at a trot under all circumstances.
4: Lameness is obvious at a walk.
5: Lameness produces minimal weight bearing in motion and/or at rest or a complete inability to move.
Essential features of a thorough examination include:
- The medical history of the horse: questions relating to past and present difficulties of the horse. Such as exercise or work requirements and any other pertinent information.
- A visual appraisal of the horse at rest. Conformation, balance and weight-bearing, as well as any evidence of injury or stress.
- A thorough hands-on exam. This involves palpating the horse, checking muscles, joints, bones and tendons for evidence of pain, heat, swelling or any other physical abnormalities.
- Application of hoof testers to the feet. This instrument allows the application of pressure to the soles of the feet to check for undue sensitivity or pain.
- Evaluation of the horse in motion. This involves watching the horse walking and trotting. Gait evaluation on a flat, hard (concrete) surface usually yields the most. Observing the horse from the front, back and both side views, to note any deviations in gait (such as winging or paddling), failure to land squarely on all four feet and the unnatural shifting of weight from one limb to another. The horse also walks and trots in circles, on a lunge line, in a round pen and under saddle. Signs of shortening of the stride, irregular foot placement, head bobbing, stiffness, weight shifting, etc. will be evaluated.
- Joint flexion tests. The horse’s limbs are held in a flexed position and then released. As the horse trots away, signs of pain, weight shifting or irregular movement are evaluated. Flexing the joints in this manner may reveal problems not otherwise readily apparent.
Diagnostic procedures are often necessary to isolate the specific location and cause of lameness. Lameness is best treated with a specific diagnosis. If there is a cause for concern based on initial examination, further tests may be recommended, including diagnostic nerve or joint blocks, radiographs, nuclear scanning, ultrasound, arthroscopy or examination of blood, synovial fluid and tissue samples.
- Diagnostic nerve and joint blocks. These analgesic techniques are perhaps the most important tools used to identify the location of lameness. Working systematically, the blocks will temporarily numb certain areas of the limb, one region at a time, until the lameness disappears. This procedure isolates the area of pain causing the lameness. Blocks can also help determine whether the condition is treatable.
- Radiographs are useful in identifying damage or changes to bony tissues. Radiographs provide limited information about soft tissue, such as tendons, ligaments or structures inside the joints, which are often the source of lameness.
- Scintigraphy (nuclear scanning). Radioisotopes injected intravenously into the horse are concentrated in areas of injury. These areas are scanned with a gamma camera, providing an image of the trouble site (horses will need to be quarantined for radioactivity after this procedure).
- Ultrasound (sonography). This procedure uses ultrasonic waves to image internal structures.
- Arthroscopy. This surgical procedure allows visual examination of the inside of a joint or tendon sheath. It requires general anesthesia but may be the only way to define the damage. Some diagnoses can only be made with arthroscopy. If deemed necessary, surgical treatment is often performed at the same time.
- Blood, synovial (joint) fluid and tissue samples. These samples can be examined for infection or inflammation . Such examinations usually require laboratory testing.
MORE ABOUT OBSERVING THE HORSE IN MOTION
The horse should be observed on both soft and hard surfaces, since different types of lameness may become apparent with different footing. In addition, lameness may only be apparent when the horse is under saddle, or it may be manifest only at liberty or on a longe line when the horse can be evaluated without the influence of the rider.
A horse’s walk and trot may be especially revealing. The slower gait of the walk makes it easier to observe slight deviations that aren’t readily apparent at a faster pace. However, the trot is perhaps most useful for evaluating lameness because it is the simplest gait, consisting of a two-beat stride pattern, and because the horse’s weight is distributed evenly between diagonal pairs of legs. In some cases the speed and concussion of a faster pace (i.e. canter, gallop) is needed to help demonstrate the lameness.
Lameness is a complicated condition, with many possible causes. Be a conscientious observer. If you suspect a problem, discontinue riding your horse and seek advice promptly. By identifying even a minor lameness and acting swiftly to correct it, you will minimize the risk of injury to the horse and yourself, and you will be rewarded by better performance and a longer useful life from your horse.