Causes of Equine Back Pain May Be Hard to Pinpoint

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Your horse’s back is like a bridge, spanning the expanse between his shoulder/front leg and his pelvis/hind leg. However, instead of a solidly supported structure like the Golden Gate, it’s more like a rope bridge. It’s anchored at either end, but aligned and supported along its length only by the long muscle bellies running parallel to it, and strong, short ligaments connecting the vertebrae.

One factor in back problems is weight. The horse’s own internal structures are heavy for him to support, let alone when you add the weight of a rider. But one factor that is entirely within our control is the stress of carrying extra fat.

If you have ever had a back problem yourself, you know the difference weight loss can make. The forces are oriented differently in an animal that moves on all fours, but the basic principle of extra weight causing more stress is the same. A key factor in helping to prevent and treat back pain is to make sure the horse isn’t overweight.

One of the first recognized primary causes of back pain was dorsal impingement or ”kissing vertebrae” — when the high spines on the tops of the vertebral bodies were touching and/or fused together. Typically found along the thoracic spine in the withers area and under the saddle, it was blamed on trauma or poor saddle fit and was easy to see on good X-rays. This problem may also be found farther back along the spine, especially in jumpers and racehorses who put their spines through more exaggerated movements than other horses.

Obviously, a poorly fitted saddle and/or bad riding can cause back pain. You should always work to eliminating bad saddle fit by either restuffing the saddle to fit the horse or replacing it entirely. Always use a good saddle pad, even a therapeutic one if needed, such as if your horse is either sensitive in his back area, in work for long periods of time or subject to a lot of uneven pressure from the rider or activity (see article on page 8 for Western saddles; our English saddle pad article will appear in a future issue). And, of course, we all should ensure good riding through lessons and practice. These are all basic good horsemanship. In this article, we’re going to assume you’ve eliminated these potential causes for back pain and are looking for other sources.

Diagnostics

Several studies have reported finding spinal abnormalities using bone scan, ultrasound or thermography in a high percentage of riding and sport horses that weren’t even suspected to have any back problems by clinical signs. This has fueled controversy in the veterinary community regarding exactly how much of a problem spinal problems are. Are these changes on studies meaningless and essentially ”normal,” since they are so common and found in horses without symptoms ??? or are we really missing the boat diagnostically when it comes to back pain'

Part of the problem with resolving the issue is that we need better diagnostic techniques, especially for finding back pain that might only be occurring when the horse is moving or carrying the weight of a rider. Some headway has been made in this direction by using kinematics ??? mathematical models for actually measuring how freely the back moves when the horse is in motion. This can be influenced by conformation, though. Pressure algometry has also received some attention. This technique uses hand held instruments to apply specific amounts of pressure along the spine and the paraspinal (beside the spine) muscles to detect how sensitive they are. What constitutes ”normal” for one horse might not for another, but the technique is at least useful in finding painful areas along the length of any given horse’s spine.

Physical examination with palpation and pressure by hand remains by far the most commonly used diagnostic measure. Abnormal responses include both exaggerated sinking/dropping when pressure is applied, and also stiffening of the back muscles, with quivering. Ear pinning, tail swishing, moving away from the examiner, and often kicking, are also indicators that the horse is in pain.

A capped ballpoint pen makes a convenient examining tool. When you run the pen down the crease in the middle of a horse’s back, the normal reaction is to dip down slightly in response to the pressure until you start to travel up the rump. As the pen moves to the highest point of the rump, the normal response to tuck under. Similar reactions will occur if you run the pen along either of the paraspinal muscles.

Many diagnostic acupuncture points are located along these paired lines, at approximately one-inch intervals.

When running the pen tip down the muscle, you may encounter one or more of these well-localized spots, no bigger than the pen tip, where the horse will obviously flinch or twitch when he feels the pressure.

Some are related to problems elsewhere on the body, but they also can signal trouble with the spine. In general, if you find only one or two well-defined spots, with no abnormal muscle responses, they may not be related to back trouble. However, if many sensitive spots are clustered together and the muscle reacts to the pen pressure by going into spasm or showing fine trembling movements that persist for several seconds or for as long as you hold the pressure, there’s a good chance you’re in an area of back pain.

With longstanding cases of back pain, the hind-end musculature is often poorly developed and may contrast with better muscling of the forequarters. Loss of definition of the back muscles may be seen if there is involvement of their nerve supply, or if the horse has been protecting himself and not using his back well for a prolonged period. On the other hand muscles that are spasmed, or swollen because of an injury to the muscle itself or a problems like tying-up may look more prominent than normal. If the problem involves the sacroiliac joint or pelvis, it is often either one-sided or worse on one side than the other and loss of muscle will be more obvious on the involved side.

The horse may adopt unusual standing positions — whatever he finds most comfortable. He may prefer to stand with one hip dropped, a leg placed either farther under or farther behind, rotated inward or outward. He may also resist picking one or both back legs up for cleaning the feet.

Watching The Horse Move

How does the horse with back pain move' Very carefully!

Although obvious lameness may be nonexistent, the movement behind is generally stiff and with limited stride. The horse will resist or refuse to engage the hindquarters well. In early cases, particularly those involving instability at a vertebral joint, symptoms may come and go completely or always be low-level but subject to sudden worsening. The signs may occur when the horse is working and may mimic tying-up. In fact, many horses with severe back pain are misdiagnosed as having tied up. The major difference symptomatically is that the pain becomes more obvious after the horse has stopped working, not during work, and typically gets worse the longer the horse stands still.

As time goes on, movement behind may become more restricted, usually with some degree of muscle loss, and the horse may actually begin dragging or scuffing his toes, sometimes confused with a neurological problem, such as EPM, or a stifle disorder.

Lateral movement and bending is also often obviously affected. The horse will stiffen and brace himself against the leg y ou are attempting to get him to bend around, in effect pushing back against you. He may comply with your cues by a correct movement of the forehand but the hind is ”locked.”

At the walk, the normal relaxed swing through the back is lost and the feel is like perching on a fence post.

The trot may be his best gait but without the ability to engage behind for either extended or faster rates.

The canter is often rough and heavy on the forehand. The horse may refuse one lead entirely and be prone to cross-cantering.

Jumping is especially problematic because to do this correctly the horse needs to bend at the thoracolumbar junction. A good bascule also requires good bending through the spine. Some horses may even begin to refuse to jump due to pain.

With back pain, the horse will tend to drag the hind end along rather than flexing his legs well. If the problem is impingement of the dorsal spinous processes, the horse may be less free with using his neck for balance as raising the head causes the back to hollow, bringing these bones into closer apposition.

On turnout, horses with back pain want to buck and kick instinctively — a movement that can release the spine — but can’t or won’t because of the pain. They may begin to buck and kick, but the movement will be feeble and with a short range of motion, often more like a hop than the impressive, ”letting loose” kick you will see from a normal horse.

Getting up and down, or rolling, may cause pain, making the horse slow and cautious, avoiding it entirely. Even simple, everyday movements for a normal horse may be painful, such as putting his head up to eat out of a hay rack, putting the head down to graze or bite at a fly.

Diagnosis And Treatment

Although progress has been slow, we are getting better methods available for diagnosing back problems. Standing X-rays can detect ”kissing spines.” Bone scans coupled with a careful examination that lets the radiologist know where to focus attention to look for both soft tissue and bone activity are useful in linking exam findings with hard evidence of the at least the location of the problem. Ultrasound is also proving helpful. Even thermography can help pinpoint problem areas.

In addition to using ultrasound to locate abnormalities, it is being studied as an aid to diagnosis with local anesthesia. As for lameness of the lower legs, improvement following local anesthesia is the gold standard for diagnostics. Interestingly, a Swedish study published in the Equine Veterinary Journal (January 2006) found that injecting the backs of even clinically normal horses with local infusion of anesthetic around the dorsal spines (”kissing spine”area) improved their freedom of motion. Unfortunately, those horses weren’t imaged by bone scan, thermography or ultrasound to see if this corresponded to unsuspected back problems.

Surgery And Meds

Surgery is an option for cases of impingement, but not for other types of problems. Even it were, odds are that surgery should be the last treatment attempted as scarring often ends up causing just as many problems.

Medication options are essentially the same as for arthritis, including aspirin, NSAIDs (like phenylbutazone or flunixin/Banamine) and herbal alternatives. We recommend reserving these options for times when symptoms are particularly severe. Muscle relaxants, like Robaxin, are also sometimes helpful in managing symptoms, especially during flare-ups when muscle spasm is a prominent feature. However, as with human back pain, response to these drugs is often far less than complete.

Fortunately, many other therapies can make the back-sore horse more comfortable. Most are lumped by veterinarians under the heading of ”alternative therapy” for horses, but they’re pretty standard fare with human physical therapists (see sidebar). Finding the combination that works best for your horse will largely be a matter of trial and error.

Bottom Line

Back pain shouldn’t always be dismissed as a secondary problem that will go away when something else is corrected. But because lameness elsewhere can cause back pain due tocompensation, a thorough lameness exam looking for other problems is always in order.

Physical-therapy options — from heat to therapy devices and acupuncture — can provide the horse with significant pain relief. We recommend you discuss these therapies with your vet as the first approach with medication only when necessary.