Thoracolumbar Pain in Horses: It's Complicated

Narrowing the cause or causes of spinal pain—from withers to pelvis—and addressing them

The horse’s spine is a single row of vertebrae joined together by ­synovial-fluid-filled pouches that allow frictionless movement. Bony projections resembling shark fins emanate from the dorsal aspect (top) and sides of each vertebra. Horses have approximately 54 vertebrae along the length of the spine, including 18 in the thoracic region (over the ribs, T1-T18) and six in the lumbar area (in the loin, L1-L6, or L1-5 in some Arabians).

Many muscles, tendons, and ligaments support the vertebrae and the articulations between them. Injuries can occur anywhere along the length of the spine and can involve any of these bony or soft tissue structures.

“Back problems are a frequently recognized problem in performance horses such as show jumpers, eventers, dressage horses, and racehorses,” says Colorado State University Veterinary Teaching Hospital professor Dean A. Hendrickson, DVM, MS, Dipl. ACVS. “The exact prevalence, however, remains uncertain, particularly as it seems to vary depending on breed, discipline, age, sex, conformation, and other factors.”

While some back issues come on suddenly (e.g., traumatic injury resulting in muscle damage or fractured vertebra), many are insidious, developing so gradually that owners easily miss the discomfort at first.

Thoracolumbar Pain in Horses: It's Complicated

“If a previously healthy back is injured and the movement at the joint level becomes asymmetric, then a horse with a mild injury can continue to function for a period of time without observable consequences,” says Sheila Schils, PhD, co-founder of equine rehabilitation therapy provider EquiNew, in River Falls, Wisconsin. “In fact, the horse may continue to perform successfully at a high level. That said, this ‘unbalance’ will eventually catch up to the horse, and performance will begin to suffer.”

This scenario, Schils says, is not unlike a poorly aligned tire. The car might continue traveling down the road; however, the misalignment forces the driver to twist the steering wheel to keep the car straight. While the driver might become accustomed to this asymmetrical position and begin to perceive it as “normal,” the tire will eventually blow.

In this article we’ll help you learn to recognize such asymmetry, along with describing solutions. 

Recognizing Back Pain

The first step toward successfully diagnosing a thoracolumbar issue involves identifying the back as the true source of discomfort. This necessitates ruling out the back as a secondary cause of pain (e.g., subsequent to neck pain, sacroiliac disease, limb lameness, and more) or congenital issues such as scoliosis. Further, more than one source of pain might be contributing to your horse’s signs, as often happens, say veterinarians. Diagnosing the exact cause of back pain in horses can be complicated and involves your veterinarian performing a complete and thorough historical and physical ­examination.

“When a horse suffers back pain, owners often report their horse has recently undergone behavioral changes such as bucking or an unwillingness to bend, move forward, or jump,” says José García-López VMD, Dipl. ACVS, ACVSMR, associate professor of large animal surgery and director of equine sports medicine at Tufts University’s Cummings School of Veterinary Medicine, in North Grafton, Massachusetts. “Complaints regarding performance, a change in head/neck carriage, reduced motion of the back when longeing, and pain on palpation of the back are also common.”

Kent Allen, DVM, owner of Virginia Equine Imaging, in The Plains, adds that avoidance behavior, poor jumping technique, and resistance to saddling can also point to back pain.

“During the moving evaluation, horses are frequently rigid in the back, resistant to moving forward, and buck or ‘bunny hop’ when weight is applied over the saddle region,” Allen says.

Equine behavior researchers from France’s University of Rennes 1 (Rochais, et al., 2016) recently reported that a horse’s reduced engagement in his daily environment might also indicate back pain. Horses suffering from chronic pain can isolate themselves, become aggressive toward humans, and show less interest in daily tasks.

Next Steps

Once you and your veterinarian suspect back pain as the cause of your horse’s performance issue, it’s time to identify the exact source of discomfort. Thanks to recent technological advances, diagnostic imaging of horses’ backs is far easier than it used to be.

Your veterinarian will determine which imaging modalities to use—radiographs, nuclear scintigraphy (bone scan), and/or ultrasonography—based on his or her manual palpation and visual inspection of the horse at rest and in motion, as well as the results of diagnostic analgesia (administering a numbing agent to help pinpoint areas of pain).

“Using more than one of these techniques will provide a more accurate, clinically relevant diagnosis,” says Allen. “Only once this accurate diagnosis has been made can treatment be instituted.”

Failing to diagnose the source of thoracolumbar pain properly and jumping straight to treatment might not manage these horses’ pain effectively, leaving them in the same or worse condition than when first examined.

Though there are many causes of thoracolumbar (the part of the spine that runs from the withers to the pelvis) back pain in horses, our sources will focus on two: osteoarthritis of the intervertebral articular facets (joints between the spinous processes and vertebral bodies) and supraspinous desmitis.

Osteoarthritis of the Intervertebral Facet Joints

Because the spine is a series of joints, it should come as no surprise that inflammation and degeneration of the cartilage lining the ends of the bones where adjacent vertebrae meet can cause substantial pain. Classic lesions found on radiographs that support a diagnosis of osteoarthritis (OA) of the articular facets include lipping and bony irregularities around the joints. The joints most frequently affected are T15-L1—a region veterinarians refer to as the thoracolumbar junction.

Veterinarians must interpret radiographs in combination with physical and lameness examination findings, García-López says, because some radiographic evidence of degeneration might be present but not actually cause the horse discomfort.

If your veterinarian diagnoses your horse with intervertebral facet joint OA, he or she might recommend a variety of therapies to ease that discomfort:

  • Corticosteroid injections (to target the inflammation), with or without hyaluronic acid (similar to treating joint pain elsewhere in the body), guided by ultrasonography.
  • Mesotherapy (injecting pharmaceuticals into the middle layer of the skin—the mesoderm—on either side of the spine to block sensory-pain fibers) using, per Allen’s recommendation, a combination of a local anesthetic, corticosteroid anti-inflammatory drug, and Traumeel (a homeopathic combination drug) diluted in saline.
  • Extracorporeal shock wave therapy (ESWT) using an 80-millimeter probe to apply 1,000-2,000 pulses at the highest setting, says Allen. Your veterinarian can repeat ESWT at four- to 12-month intervals, based on the horse’s response.
  • Off-label bisphosphonates (drugs that inhibit bone resorption, FDA-approved for managing navicular pain), even though little evidence supports their use for back issues.

Schils says you then need to rehabilitate the arthritic facets to address incorrect joint spacing in concert with the existing muscle asymmetry.

“I have found the diagonal movement at the trot seems to bring relief by providing stability to the spine, and some limited equine research supports that,” she says. “For horses with OA of the facets, movement in straight lines is always preferable in the early stages of rehabilitation. When turns are necessary, they should look more like octagons, not circles.”

Once the horse seems comfortable at the trot, add canter sets into the rehabilitation protocol to help open the joint spaces and improve total spinal flexibility, ensuring the horse continues traveling in straight lines. Striking a balance between spinal stability and flexibility is essential to overall spinal health, Schils says.

“For example, if they are a jumper, we work on canter pirouette-type turns to keep the horse straight,” she says. “In addition, before any turn or change of direction, three strides of a straight line should be performed. This comes from human research on the number of strides it takes for an athlete to rebalance.” 

Thoracolumbar Pain in Horses: It's Complicated

Supraspinous Desmitis

The supraspinous ligament lies above the dorsal spinal processes, running the length of the vertebral tract from the seventh cervical vertebra to the sacrum (pelvis). Direct trauma can damage this ligament, as can overstretching during exercise, particularly jumping, causing inflammation (desmitis). Injuries to the supraspinous ligament are similar to those that occur with other important ligaments, such as the suspensory ligament at the back of the cannon bone. As with most soft tissue injuries, ultrasonography is the diagnostic tool of choice, and the location to focus on appears to be the region spanning the thoracolumbar junction. 

Schils says she typically sees supraspinous desmitis occur as a result of ­overextension of the ligament and/or pathological (involving disease or damage) spinal rotation. She says rehabilitation of supraspinous desmitis problems must focus on improved weight-bearing of the limbs, so the spine isn’t solely responsible for movement.

“Supraspinous desmitis is typically a self-limiting injury (it heals on its own) in horses, and the lesion should scar in after a few weeks,” says Allen. “If there is significant pain or swelling associated with the injury, the horse will likely benefit from shock wave therapy and/or the administration of NSAIDs (non-steroidal anti-inflammatory drugs) while they have time off from ridden work.”

Schils says stabilizing the back during the initial stages of supraspinous desmitis through trot work can help.

“How long this process takes depends on how long things have been wrong and the degree of the asymmetry and the pathological rotation,” she says. “Typically, by the time I see a horse, they are fairly asymmetrical and quite uncomfortable. I usually say it will be a year before the horse can walk out of the stall in a different biomechanical stance without us reminding them how to change their posture.”

Although that might seem like a long time for recovery, Schils emphasizes that your horse can continue to perform during this period.

“If the muscle training of the horse previous to the back pain is to jump 1.60 meters, then the horse may have to drop down in height during competition as new muscle memory is developed,” she explains. “I would estimate it typically takes between three and six months before a horse is back competing at their former level. However, the rider must be vigilant during these early returns to performance to make sure that the horse is maintaining the biomechanical improvements necessary for long-term improvement.” 

Getting Back in the Game

Little published research exists regarding the optimal number of days off from competition, the time to recovery, and chances of relapse for the various causes of back pain, says Hendrickson. Overall, though, advanced diagnostic tools and a growing number of treatment options seem to be improving a horse’s chance of recovery. 

“In one study, 57% of 190 horses with a general diagnosis of back pain recovered,” he says.

As the diagnosis becomes more pointed, so do the data regarding outcome. For example, horses with soft-tissue back injuries such as supraspinous desmitis have a better outcome (about a 75% recovery rate with recurrence in fewer than one-third of properly managed cases) than those with bony issues, such as fractured vertebrae, Hendrickson says.

“There is hope that we are helping these horses become more comfortable and return to work successfully through research in this area,” says Schils. “A retrospective study of 241 horses with (muscle spasms due to) back pain found that 80% of the horses had a graded improvement in muscle spasms after two functional electrical stimulation treatments. In addition, 60% of these horses showed a sustained improvement for a minimum of two months. Through advances in management and technology we are making important changes in the well-being of the horses we care for.”

Take-Home Message

A complete physical exam, diagnostic analgesia, and imaging involving radiology and ultrasonography and/or nuclear scintigraphy play important roles in determining the source of a horse’s back pain. For the best outcome, combine therapies that help control inflammation and pain with rehabilitation modalities recommended by a qualified veterinarian or equine therapist. Finally, avoid the urge to simply rest your horse in the face of thoracolumbar discomfort, as this will slow the recovery process.

“In addition to the fact that movement helps fix the problem of muscle imbalance and poor muscle memory, horses will be happier if they are allowed to continue to do their job,” says Schils.