Recognized as a factor in contributing to or even causing lameness, equine back pain can affect almost every aspect of performance. If you notice a change in gaits, especially when the hindquarters are engaged, or if there is sensitivity to pressure, whether from grooming or simply by touching the area, or aggression under the saddle, you may be facing a horse with back issues. This is not surprising when you consider that he uses it for just about all his movements. The vertebrae, joints, surrounding tissues and nerves are critical for even the most basic actions. That’s why even a slight trauma can cause discomfort and can escalate into a full blown pathology if not detected and treated early.
The Physics of Locomotion
To better understand back pain in relation to the physics of locomotion, start with basic equine anatomy and biomechanics. There are anywhere from 51 to 57 individual vertebrae that act as protection of the spinal cord and associated nerves. There are more than 260 joints that act as connectors between the vertebrae, ribs, sacrum and pelvis. And, because the spine and related muscles are integral components to the attachment of the limbs, there is a symbiotic relationship between them that enables the spine itself to be flexible.
Mobile in three directions—dorso/ventroflexion (up and down), lateroflexion (side to side) and rotation, the vertebrae have a specific range of motion for each movement. For instance, in the cervical vertebrae, there is a relatively large range of dorso/ventroflexion and lateroflexion. The lumbar region includes rotation, of which there is very little in the sacral region. In the tail, there is dorso/ventroflexion and lateroflexion, but no rotation at all.
The position of the spine is determined by the gait. The walk, for instance, combines thoracic lateroflexion and rotation in the lumbar section, with cervical dorso/ventroflexion, which gives the walk a swinglike motion. The trot, however, exhibits little dorso/ventroflexion movement, which is mainly felt in the thorax and neck, while the canter puts emphasis on the lumbar and sacral regions through rotation and dorso/
The Conformation Element
The Well Conformed Back: The model back has three elements. One is well-defined withers that are higher than the croup, which should be long and curved. The backbone should arch upward imperceptibly—the degree will vary from horse to horse. The topline, measured as the distance between the peak of the withers to the peak of the croup, should be less than the underline—measured as the distance along the belly between the front and rear legs.
The Long Back: Labeled as such when the back measures over one third of the overall body length—from the peak of the withers to the peak of the croup—a horse with a long back tends to be flexible, making for easy lead changes and a quiet, smooth ride. But he also tends to have long, weak loins, which can affect his ability to develop the back and abdominal muscles necessary for speed or collection. In addition, this type of back is more likely to become fatigued under saddle, due to abdominal weakness, which can lead to its becoming swayed over time. And, because the loins and hindquarters may cause exaggerated movement, it can result in discomfort from strained muscles translating into short, stiff gaits.
The Short Back: Measuring less than one third of the overall body length from the peak of the withers to the peak of the coup, this back type predisposes the horse to better support the weight of a rider, especially if he has developed good muscle tone, and to be agile and athletic as well. However, as with the long back, there are disadvantages. A short back may lack flexibility and may be inclined to become stiff, rigid and, if the vertebrae are especially small, may also exhibit difficulty in bending. As a result, the stride will become stilted and unnatural, causing overreaching, forging, or clipping in the hind legs if they are not aligning properly. Also, as he ages, there will be more of a threat that the short-backed horse will develop spinal arthritis.
The Sway Back: Appearing as a concave dip in the center of the back, spanning between the withers and the croup, and which is accompanied by a high head carriage to compensate, this condition is associated with a long-backed horse who suffers from weak surrounding ligaments. Age also seems to play a role, as seen in broodmares and seniors. But sway back can also become a problem for a horse that is inactive (conditioning supports proper ligament and muscle development), or that has suffered an injury due to overuse, has carried heavy loads, or is an immature horse that has been worked too intensively. Also, there appears to be a congenital type of sway back associated with very young horses whose histories trace back to certain lines of the American Saddle Horse.
When carrying a rider, the swayed-back horse may become sore from lack of support coupled with the rider’s weight. Plus, with the rider positioned behind the center of gravity, which can affect his/her balance, the horse will be additionally burdened when attempting to elevate his back for collection. With regard to impulsion, the swayed-back horse, whose rear end is less connected with his front end, is unable to create the necessary rigidity for immediate acceleration.
The Examination Process
Given that there are any number of injuries or activities that can be attributed to back pain, it is very difficult to determine the cause; nevertheless, there are two categories to which pain is generally ascribed.
Primary: Resulting from lesions of the skin, muscles, connective tissues, nerves, joints and bones, this type of pain generally results from a traumatic injury, i.e. ill fitting tack, rider imbalance, pasture accident.
Secondary: In addition, back pain can result from an underlying lameness—hock pain is a typical offender. However, any lameness can result in back pain when you consider that the limbs and back are closely linked.
A comprehensive veterinary examination can help isolate the area of concern. Describe to the vet any gait abnormalities and when they first occurred, such as trouble with canter on a specific lead, or sudden resistance to leg and rein when doing lateral work or when bending in a circle. Also, note any time-related changes in mobility, i.e. canter quality deteriorates as the schooling session progresses.
In the clinical phase of the exam, the emphasis on lateral bending in the walk and canter, accompanied by palpating muscles, ligaments and bone structures, can provide valuable information as to the site of a spinal lesion. More specific techniques are also available, i.e. radiography, ultrasound, electromyography (used to examine muscle and neurological involvement), to focus on areas of concern.
Eliminating back pain can be as simple as refitting your saddle or bridle. The saddle should conform to the horse’s back without forming areas of pressure. The saddle should be level from front to back, and be positioned to allow free movement. The bridle should be fitted properly to avoid resistance to the headstall or bit, which can lead the horse to flatten or hollow his back.
Increased turnout time can also be a tonic for sore backs, especially if there is a great deal of down time spent in a stall. Movement is the key here.
Several medical solutions are available, too. High-tech therapies such as shock wave or therapeutic ultrasound may help. A variety of meds are commonly prescribed, from muscle relaxers to nonsteroidal anti-inflammatory drugs (NSAIDs). Intramuscular hormone injections that were originally used for broodmares before delivery have been found to be beneficial in some situations, as they relax tight pelvic muscles and ligaments. Corticosteroids can help reduce inflammation and relieve pain. Feeding supplements such as vitamin E and selenium, along with electrolytes to enhance muscle function, may also be an option.
If you want to go the alternative therapies route, acupuncture is an approach that often provides relief. Having been practiced for over 3,000 years in China, acupuncture works on the principle that areas where the energy is blocked can be ‘opened,’ and areas where there is too much energy or inflammation can be ‘turned down.’ Chiropractic care, another non-invasive approach, uses the inherent recuperative powers of the body, while addressing the intimate relationship of the spinal column and the nervous system. Laser, magnetic and massage therapies may also help relieve tense muscles. In all cases, consult with your veterinarian when considering the options.
Reviewed by Dallas Goble, DVM, Dipl. ACVS, and head veterinarian of the Budweiser Clydesdale Herd Health Program.