If your trail horse pulls up lame, call your veterinarian immediately, and ask for a lameness exam. Here, I'll go through each step of the lameness exam. Plus, I'll give you the lameness scoring system from the American Association of Equine Practitioners. The more you know, the better you can fully participate in your horse's recovery.
Step 1: Observation
During a lameness exam, your veterinarian will first observe your horse from a distance. He or she will observe your horse from the front, behind, and both sides to look for muscular asymmetry.
Here's why: Your horse is a master compensator. If he begins to develop soreness in one location, he'll compensate for it with subtle changes in how the leg is moved, how a foot might land, or by redistributing weight. These changes will often show up in your horse's resting posture, as well.
Few horses stand perfectly squarely all the time, but most, when standing quietly, will settle into a posture that feels right to them. Assuming they have a good trim and are receiving the correct information from the ground, they should stand squarely.
If your horse is sore, observable changes at rest might include not standing squarely, e.g., feet positioned in front of or behind the spot that would be perpendicular to the ground; preferentially resting a limb; and weight shifts.
Step 2: Touch
Your veterinarian will then move in closer for a hands-on exam. He or she will palpate (explore by touch) your horse's muscles for tone.
A relaxed muscle at rest ? even in a very fit horse ? has the same consistency as a roast of beef, although the postural muscles along the spine have somewhat higher normal resting tone, because they are "working" to hold the spine in alignment even when standing still.
The gluteal muscles of the rump are also somewhat difficult to evaluate, because the skin there is very thick and tight, with a generous layer of fat between skin and muscle. If muscle tension/hardness or sensitivity to touch is found, carefully note the location.
Next, your vet will carefully check the full length of each leg for any heat or unusual swelling, comparing it to the opposite side if there's any question. He or she also will note any unusual prominence to the veins from side to side, which often indicates inflammation.
This part of the exam also includes picking up the foot to inspect the sole and frog, check hoof wall temperature, and compare the hoof temperature to the rest of the leg. Each joint will be gently and gradually flexed, looking for any sign of pain (such as your horse pulling back).
Your vet then will use hoof testers (pliers with large, rounded jaws) to check for hoof sensitivity. This test can reveal such conditions as a sole abscess, laminitis, or a stone bruise.
Step 3: Sound in Motion
During this step, your veterinarian will watch and listen to your horse moving from the front, back, and side. He or she will observe and listen first at the walk, then at the trot and on a circle if nothing is obvious at the walk.
To tell where your horse may be "off," first develop your ear! Practice listening to the clip-clop noise made by your horse at the walk and trot. A sound horse lands with equal force on each foot, slightly louder in front than behind.
When your horse has pain, you can actually hear a softer landing on the sore leg, with one or more louder sounds as he shifts weight to compensate. His gaits will also lose their rhythmic sound as he rushes to unload the sore leg and more quickly stomps down the compensating legs.
If your horse has a Grade 2 lameness up front, he'll often just shorten up his stride at a walk, but move with an even stride length from side to side. This makes it very difficult to detect.
With a hind-end lameness, your horse is more likely to shorten stride only on the sore side. In addition, he'll look "disconnected" front to hind. Toe dragging/scuffing, sometimes to the point of stumbling, is another common sign of pain.
Step 4: Flexion Testing
This testing method is still a valuable diagnostic tool, but is falling out of favor somewhat since it's possible to make any horse move off badly if you crank on the joint too much.
The amount of flexion or extension you're able to impose on a joint isn't necessarily the same as how far it was meant to move. To see what I mean, practice manipulating the joints of your own hand. Hold a finger straight, then force it front and back. You'll feel pain when you force it beyond where it would normally go.
If your horse seems to be objecting to a flexion, your veterinarian may go to the other side to see how your horse reacts to the same flexion. Or, your vet may walk your horse a few minutes to let him relax.
Note that if your horse appears to be in pain during a flexion text, the real cause may actually be the extra weight the opposite leg is carrying.
Step 5: Nerve Blocks
Unless there's a glaringly obvious problem, such as a bowed tendon, nerve blocks (perineural analgesia) are typically the next step in a lameness examination. By numbing select leg structures, your veterinarian will better be able to track down the source of your horse's pain.
The blocking begins with the paired digital nerves at the back of the pastern. Called a low volar block, this will take out most of the foot, including the hind foot and the sole, part of the coffin joint, and part of the pastern joint.
The anterior (back) portions of the foot and pastern structures are supplied with the nerves that branch off from the digital nerves at fetlock level. Therefore, to completely block the foot, the nerves are blocked at fetlock level ? called a high volar block. The only problem with a high volar block is that it'll also anesthetize the fetlock.
An alternative to the high volar block is a ring block, where anesthetic is injected under the skin of the upper third of the pastern, in a line across the anterior (front) 180 degrees of the bone column.
Step 6: Joint Blocks
When the fetlock, knee, shoulder, hock, stifle, hip, or sacroiliac joints need to be anesthetized, the usual procedure is to inject directly into the joint. Joint fluid is usually withdrawn first, which can be studied for further clues.
The hock and knee can also be blocked. Other areas commonly blocked are the origins of the suspensory ligaments, bursae, and the sacroiliac region.
Lameness Scoring System
The American Association of Equine Practitioners has developed a system for scoring lamenesses:
0 ?Lameness not perceptible under any circumstances.
1 ?Lameness is difficult to observe and isn't 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.
Eleanor M. Kellon, VMD, of Equine Nutritional Solutions in Ephrata, Pennsylvania, is an authority in equine nutrition and expert in the field of equine nutraceuticals. Her most recent book isHorse Journal Guide to Equine Supplements and Nutraceuticals (Globe Pequot Press).
Photos by Dusty Perin