Equine vet column: Back pain proves a tricky problem to solve

The back is the most complex and expansive locomotive structure in a horse's body. The equine back is made up of:

• A total of 23, or 24 thoracic and lumbar vertebrae between the withers and tail-head;

• The spinal cord running through the centre of the vertebrae;

• The muscles and ligaments that hold the vertebrae together in alignment;

• The articular joints formed between the vertebrae;

• The multiple muscles anchored to them, connecting the spinal column to the appendages.

a skeleton demonstrating considerable arthritis of the facets of the back

Every movement that a horse makes, from poll to tail, originates in the nerves of the spine and every muscular action, from feet to ears, interconnects in some way with the muscles and tendons of the horse's back and neck.

It is, therefore, little wonder that pain originating in any structure of the back can have effects throughout a horse’s body. Vice-versa, any injury in the body can affect how the horse uses its back, which in turn can lead to aches, strains and spasms.

As many people will know and understand, having had discomfort in their own back, pain inhibits movements, limits ability to perform and affects attitude towards work.

Clinical signs

The subtle signs that a horse is experiencing back pain can easily be overlooked.

Learning to distinguish evidence of discomfort and seeking help and advice early is so important in order to address small issues before they develop into more serious problems.

Unlike limb pain, which is usually reflected in identifiable lameness, back discomfort frequently lacks a readily discernible focal point or characteristic gait effects.

A horse with a painful front limb produces a distinctive ‘head nod’ when trotted up, however the ‘typical’ characteristics of back pain can be extremely varied.

It is often said that the most common symptom of a back problem is behaviour changes/issues. With often only vague indications to go on, you can easily misinterpret manifestations of a sore back as signs of limb lameness or of a training problem.

Even when fairly certain that your horse is reacting to back pain, determining whether its muscles, ligaments, vertebrae or multiple structures that are involved is not easy.

Identifying the cause of the soreness may or may not be possible; sometimes even sophisticated diagnostics aren't able to fully visualise an abnormality hidden under thick muscle or within dense bone.

Yet, as uncertain as diagnostics may be, a methodical, common sense approach can help towards getting a diagnosis.

A horse with back pain will usually make strong behavioural statements, these may include:

• Evading contact during grooming;

• Pinning ears back or biting while being tacked up;

• Sinking, bucking or rearing when mounted;

• Restricting rolling and lying down;

• Regularly rearranging the bedding to be able to stand in a more comfortable position;

• Develops annoying under-saddle habits, such as tail swishing;

• Resisting backing up;

• Resenting lateral work, often in one direction;

• Acts stiff behind and seems reluctant to fully engage the hindquarters;

• Is fidgety, tense and unable to concentrate;

• Becomes less responsive to your aids as a riding session progresses;

• A 'sore-backed' jumper may produce less thrust, jump with a fixed, hollow back, rush to or away from fences or refuse to jump combinations.

A number of issues can cause pain, but one of the commonest is ill-fitting tack, which creates pressure points that can lead to muscle and soft tissue soreness.

Even when the tack fits well, rider asymmetry can place uneven pressures on a back. Other sources can include traumatic injury, from a fall or accident, or general wear and tear, which can lead to muscle strains and sprains as well as, in time, arthritic changes in the vertebrae.

Diagnosis of back pain

Finding a problem in a horse’s back can require some careful investigation work.

Sometimes the source of back pain is elusive, the problem may be in a limb; the back pain being secondary to a limb lameness, and so therefore the source of the lameness must be identified first.

Therefore, investigations should usually start with a complete lameness assessment/evaluation.

A detailed history may also yield significant clues, for example, if a horse is generally comfortable moving laterally to the left but not to the right, or if it resists only when asked to collect or back up. Tail swishing is another sign that may indicate pain.

A visual examination can identify any swelling, atrophy (muscle loss) or crookedness. Your vet will also want to watch the horse move through all the paces and conduct a neurological examination if any nerve damage is suspected.

The next step will be a hands-on examination that includes manually palpating the horse’s back along the spine. Many horses with back pain respond to touch or pressure along the back if you palpate the lumbar muscles, these horses will either tense up to try to protect themselves from that touch, or sink downward to try to get away from it.

Some will tense upward if you touch the tips of the spines of the vertebrae.

Once a particular region of the back that seems to be causing pain is identified, a vet may try injecting the area with local anaesthetic to see if the horses gait improves (nerve blocking).

Depending on the response to this x-rays may then be obtained. The images need to be interpreted with caution as even if an x-ray shows arthritic changes or other abnormalities in the vertebrae, it doesn’t necessarily mean that the bones are the source of the pain.

a horse's back being safely xrayed with a xray plate holder

Many horses can have severe changes on x-rays—such as 'kissing' spines, a condition in which the dorsal (upright) processes of the vertebrae come into contact with each other – but never experience any ill effects.

This complicates diagnosis because pain may be coming from something else. If x-rays are used to make a diagnosis of kissing spines, nerve blocking should also be used to try to block that area, to make sure the block makes a significant difference to the horse gait, or by performing nuclear sintigraphy to confirm that the area of ‘kissing spines’ is clinically active and therefore painful.

Another difficulty with x-rays is that it is almost impossible to obtain clear views of the sacroiliac region, where the last lumbar vertebra meets the pelvis.

Unlike other joints along the spine, which have little range of motion, the lumbosacral joint rotates almost 30 degrees, which enables the horse to pull the hind legs up under themselves. Damage and injuries to this area are relatively common in sports horses.

Perhaps the ‘gold standard’ imaging modality in back pain cases is nuclear scintigraphy, which involves injecting the horse with a radioactive tracer that accumulates in metabolically active 'hot spots' in bone tissue, which might indicate inflammation or injury.

Even with the best diagnostic technology, however, in some cases the specific source of a horse’s pain might remain a mystery.

Treatment options

The best course of action depends on the diagnosis.

In some cases, finding the most effective treatment may take some trial and error, and in the end, often a range of treatments will be used in combination;

• Rest: Even just a week or two off from work may be enough to ease muscle pain in a horse’s back.

• Systemic medication: Non-steroidal anti-inflammatory medications, like Bute, can be used especially in acute injury or after a traumatic event along with an appropriate rest period.

• Rest alone is not recommended for many types of back pain. Too much time away from training can lead to loss of muscle tone, which can exacerbate an injury and complicate the horse’s return to work.

• Localised medication/injections: A common treatment for back pain is to inject corticosteroids or local anaesthetics directly into the affected area to control pain and inflammation.

• Another medical approach, called mesotherapy, is useful to treat soft-tissue pain along the length of the back. This involves using tiny needles and injecting small amounts of medication just under the skin in the painful area.

• Shockwave therapy: Extracorporeal shockwave therapy (ESWT) involves sending tightly focused, very high-energy pressure waves through body tissue to ease pain and stimulate healing. This needs to be performed by a vet; typically after x-rays or other imaging technologies have pinpointed the specific areas where osteoarthritic changes in the spine are causing the horse pain.

• Massage/physiotherapy: Manually palpating or manipulating the muscles (or using ultrasound/pulse wave therapy) is widely practised on sport horses. It is thought that the practice relaxes tense muscles, increases circulation to reduce localised pain and swelling in the area.

Scientific research into physical therapy has been limited, but some studies have shown that it can increase the range of motion in a horse’s limbs and improve overall performance, and anecdotal reports of its usefulness are widespread.

• Stretching exercises: Involving motions such as lifting and manipulating the limbs as well as 'carrot stretches,' asking the horse to bend his neck to reach treats held at different points, can also help to ease tense muscles.

• Both massage and stretching can be done routinely, as part of a horse’s fitness regimen, to help him stay more flexible and balanced

• Chiropractic: Another method of manipulating the musculoskeletal system is chiropractic care, which focuses primarily on the vertebrae. Limited studies have shown that chiropractic manipulations may improve how a horse moves, but in-depth research on the practice has not been done.

• Acupuncture: The technique involves inserting very thin stainless steel needles into the body at specific points. Chinese tradition talks of using acupuncture to 'increase energy flow,' but a more modern approach allows that the technique is stimulating muscles and nerves to cause relaxation and ease pain.

Acupuncture is never intended to be a primary treatment for an injury, but veterinarians may suggest it as a way to help ease pain in conjunction with traditional approaches.

When it comes to protecting a horse’s back, it is important to first make sure the saddle fits. Beyond that, the same measures that can protect soundness will also reduce a horse’s risk of developing a sore back.

Before work, spend time warming up with straight lines, then serpentines and circles. Also, avoid repeating the same manoeuvres more than a few times in each session.

Varying the riding routine by alternating arena workouts with hacking or other types of exercise will help to keep a horse mentally engaged as well as physically sound.

Finally, it is important to give horses as much turnout time as possible. Moving around grazing gives the opportunity to stretch out and relax all of muscles.