The Incredible Equine Neck
From perils to preservation tactics
We often base our first impression of a horse on the conformation of his head and neck, noting how his neck comes out of his shoulder and how “clean” it is at the throatlatch. Horses frequently race neck and neck, sometimes winning by one. And we can’t overlook the tumult performance horses’ neck flexion has caused in the industry in recent years. But for all the focus on the horse’s neck, sometimes we overlook how vital it is for routing crucial nerves around the body and how its health contributes to the horse’s overall soundness.
In this article we will explore equine neck anatomy, risks for injury and disease, and associated therapy, so you can give your horses the best chance for a strong neck and an athletic future.
Equine Neck Anatomy
The equine neck is a complex structure in which more than a hundred muscles support and move seven very large bones called vertebrae. The sensitive spinal cord and peripheral nerves intersect each vertebrae before continuing down the forelimbs.
A horse’s neck stretches much longer than that of most other herbivores, says Hilary Clayton, BVMS, PhD, Dipl. ACVSMR, MRCVS, professor and McPhail Dressage Chair Emerita at Michigan State University’s (MSU) College of Veterinary Medicine, in East Lansing, and president of Sport Horse Science, in Mason, Michigan. The seven cervical vertebrae connect to form an S-shape from poll to withers. The top two are designed a bit differently than the rest and work to support and move the head. The other five—some of the longest vertebrae in the horse’s body—curve downward to the base of the underside of the neck, at the chest, where they are situated such that the adjacent thoracic vertebral processes can jut upward to form the withers.
The horse also carries his neck in a more vertical position than his fellow grass-eaters—a feat requiring significant muscular support. Consequently, most of the neck’s topline isn’t defined by bone, but by muscle. Lots and lots of muscle, in fact. The neck comprises 6% of the horse’s body mass, and Clayton says the vast majority of that is muscle.
Extensive dissection work on the equine neck over the past couple of years has revealed that a system of short stabilizing muscles—called axial muscles—encase the vertebrae and hold them in place. There are also several long muscles that move the neck up, down, and from side to side. Both of these muscle types act in harmony to move and stabilize the horse’s neck, Clayton says.
The vertebrae are strong and mobile—meaning they can absorb shock fairly well, explains Richard Hepburn, BVSc, Dipl. ACVIM, CertEM, MS, MRCVS, recognized specialist in equine internal medicine at B&W Equine Hospital, in Gloucestershire, U.K. Except for those closest to the poll, the vertebrae are deep-set in a low position in the neck, which helps protect the spinal cord from injury.
The equine neck also houses the trachea (windpipe), esophagus, jugular vein, many tendons and ligaments, and cartilage. And nestled deep within the vertebral column is the ever-critical primary nerve line: the spinal cord.
The Biggest Worry: Spinal Cord Compression
The most serious equine neck condition, says Hepburn, is spinal cord and peripheral nerve compression. Compression can occur due to congenital (present at birth) spine malformations, injuries that break or reshape the bone, degenerative joint disease, or a combination of these.
Spinal cord compression’s telltale sign is ataxia, or a lack of coordination in gaits. Other neurologic signs affecting muscle strength, skin sensation, and body awareness usually accompany ataxia, says Jean-Marie Denoix, DVM, PhD, director of the Centre d’Imagerie et de Recherche sur les Affections Locomotrices Equines, in the town of Dozulé, in Normandy.
In these cases, “basically, there is a marked reduction in the horse’s subconscious feedback to where his/her body is,” explains Narelle Stubbs, PhD, BSCPT, MAnimPT (VetPT), associate professor of equine sports medicine and rehabilitation at MSU’s McPhail Equine Performance Center. “They are walking like they are somewhat drunk and don’t know where the ground is.”
While most grades of compression-related ataxia are not life-threatening, they are frequently performance-limiting. Some horses have defied the odds and recovered to race or compete, but the majority must be retired or euthanized.
More difficult to detect are peripheral nerve signs or “referred pain and paresthesia (pins and needles and numbness),” Stubbs says. For example, a compressed or irritated nerve root in the neck can refer signs to the forelimb with or without local neck pain. “Liken this to when you hit your ‘funny bone’ on the point of your elbow, which is actually your ulnar nerve,” she says. “You feel sharp pain and tingling into your fourth and fifth fingers, as this is where the nerve supplies. Not being able to speak to horses, it is therefore difficult to determine the presence and severity of referred pain from the neck into the forelimbs.”
In other words, some horses might display signs of poor performance or even lameness as a result of neuromuscular dysfunction originating in the neck.
Cervical Joint Arthritis
A fairly common neck issue in ridden horses, particularly as they age, is degenerative joint disease or osteoarthritis (OA) of the cervical intervertebral synovial (facet) joints. When the joint cartilage in this region is damaged or worn, it causes changes in the synovial fluid that lubricates the joint, thickening of the joint capsule, and altered neck muscle control. Arthritis results, seen as inflammation and potentially pain in neck facet joints. Hepburn and Stubbs explain that the most common combination of signs is a loss of or change in performance, changes in behavior, and/or forelimb lameness.
Arthritis has secondary effects on the neck’s surrounding muscles. “A lot of the changes we see around the joints occur with the axial muscles,” Hepburn says.
These “dynamic stabilization muscles,” which we know are vital for normal neck function and motion, are inhibited by facet joint inflammation and pain, making neck arthritis a vicious cycle of inflammation, pain, and dysfunction, Stubbs adds.
When this occurs, the horse compensates by contracting his long neck muscles in an attempt to stabilize the neck during locomotion and performance. This usually makes the entire neck stiff, Clayton says. Unfortunately, even when veterinarians successfully treat the primary source of neck pain with medication, the short stabilizing muscles do not automatically resume their normal function. “The resulting loss of stability between adjacent vertebrae sets the stage for the development of further arthritic changes,” she adds, “and so the cycle continues.”
Accidents Can Happen
The horse’s large, mobile cervical vertebrae remain well-protected and fairly resistant to physical insult. “It actually takes quite a lot of effort to damage the bones in the horse’s neck,” Hepburn says.
Still, traumatic neck injuries can happen. In the U.K. Hepburn sees them mostly in steeplechase horses hitting obstacles head-on. But rotational falls, where the horse flips over his head, usually over a cross-country obstacle, can also cause serious trauma, he says. That’s particularly true if the horse hits the ground at the junction of the neck and shoulder. Such blows can cause fractures, accelerate arthritic degeneration, or compound the effects of developmental disease, such as vertebral malformations, with long-lasting consequences.
A fractured vertebra can also cause spinal cord damage, leading to ataxia and other neurologic disorders such as incontinence and tail weakness.
Fortunately, these complex diagnostic scenarios are uncommon. “The vast majority of neck trauma cases that we see do not have any neurological component,” Hepburn says. What do veterinarians see most as a result of such a fall? “Sore necks. The pain and damage is most often soft-tissue-related and can be treated with rest, analgesics, and physiotherapy.”
Muscle Trauma, Indentations, & More
The neck muscles sometimes also suffer injury from trauma, says Hepburn, but the result is typically short-term stiffness, soreness, and limited lateral bend/flexion. Occasionally, forelimb lameness, short strides, unusual head carriage, loss of performance, or behavioral changes accompany these signs. Most cases of neck muscle soreness resolve with time and anti-inflammatory pain medication. If a veterinarian links your horse’s muscle soreness to how you’re riding or training the horse, however, modifying training techniques to avoid the painful position becomes the treatment strategy (more on this in a moment).
A little dip in your horse’s neck muscle is most likely the result of a slightly damaged superficial nerve, says Hepburn. However, it’s rarely anything serious. And, in fact, he says that in the U.K. these “prophets’ thumbprints,” as they’re often called, are so common they are described on official registration paperwork used to identify horses.
The indentation itself is an atrophied (wasted) or undeveloped muscle that has never received—or is no longer receiving—nerve signals to keep it active, Hepburn says. The greater the damage is to the nerve itself, the more nerve branches it affects and the larger the resulting dip.
Otherwise, neck muscle issues—unrelated to riding or trauma—are uncommon, he says. “The neck does not seem to be a primary site for myopathies (skeletal muscle disorders), which occur more frequently in the back and the hindquarters,” such as tying-up.
The Way We Ride
We’ve established a lot can go wrong with our horses’ necks—and much of it lies out of our control. But there’s an important link between the wellness of our horses’ necks and how we ride, our sources agree, and we can adapt our training styles to prolong their performance years and keep their necks healthy. The key lies in being flexible … on a number of levels.
“The neck is absolutely fundamental to the way a horse moves,” Clayton says. “If the horse is going with his head in the air and his neck hollow, his back is going to be more hollow, so he’s more likely to get arthritis, and he’s not going to perform the way we want him to in competitions.”
But riding a horse in standard dressage “contact” can lead to neck issues, as well, Hepburn adds. And, says Clayton, that’s especially true in horses with congenital narrowing of the spinal canal.
“When you put a horse in a classic contact position, that’s supposed to be very good for the soft tissues (muscles, ligaments, and tendons),” Hepburn explains. “But it also narrows the vertebral canal and the intervertebral foramen (the opening between vertebrae), so you increase the risk of spinal (as well as peripheral nerve root) compression to occur.”
So what’s a rider to do?
“A little bit of everything is probably good for you,” Hepburn says, referring to arena exercises. “Doing all of one thing is going to highlight the negative effects.” Don’t ride a horse on contact all the time, he adds, especially when the horse is not working. Riders should allow their horses to lengthen and stretch their necks out and down periodically during training.
Human sports medicine researchers have shown that pain in the muscle and fascia (connective tissue that surrounds muscles and muscle groups) accounts for 80% of neck and back pain in people, Stubbs adds. “Research has shown that patients with neck and low back pain syndromes should change their posture and gait/locomotion cyclical loading pattern (e.g., subtle changes in running style) every 10 minutes,” she says. “This has markedly improved rehabilitation outcomes and performance and reduces the risk of further injury in people. Therefore, every 10 minutes alter your horse’s head and neck posture and work routine.”
And if you go out for a leisurely ride, loosen those reins.
The Exercises We Can Do
A horse that’s suffered a neck injury or is dealing with neck pain or stiffness from arthritis or poor riding can benefit greatly from physical therapy and specific exercises, say our sources. In fact, they can be very beneficial even to horses without neck pain.
But it’s important not to do just any old exercises. The wrong kind of neck manipulation could actually make the horse feel worse.
Clayton says she encourages owners to strengthen the short stabilizing muscles around the cervical vertebrae with very specific dynamic mobilization exercises (designed to promote movement in the joint tissues). Using a carrot as bait, handlers can bring horses’ chins to their upper chests, between their knees, between their fetlocks, and around to each side in a low head position, maintaining these positions for at least three to five seconds. Clayton, Stubbs, and colleague Nicole Rombach, APM, MEEBW, CBW, MSc, PhD, recently used automated motion analysis technology and ultrasound evaluations to confirm that these exercises mobilize the joints in the neck and back and, more importantly, strengthen the short stabilizing muscles. That’s likely to improve neck and back health, Clayton says.
“I really think those exercises are important for preserving spinal health along the whole length of the horse’s spine,” she says. “Even healthy horses. Even my horses!” Owners should contact a licensed equine physiotherapist for exercise training.
Although horses’ necks are heavily muscled structures that protect big, sturdy vertebrae and more fragile structures lying beneath, disease and trauma can still occur. Horse owners must watch for signs of neck issues and have a veterinarian evaluate a horse that displays stiffness, soreness, or ataxia. While some neck issues can have lasting consequences, many can be resolved through veterinary management in conjunction with proper physical therapy and adjusted training techniques.
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