April 22, 2024 
“He’s due for work.”
“She might need injections.”
“It’s time for some routine maintenance.”
They’re all different expressions for the same, common veterinary treatment in horses. For many equine athletes, joint injections are an important part of a regular, veterinary care program. The reason for that is simple: in competitive horses, or those with an injury, injections can help to prevent osteoarthritic pain; both now and, ideally, in the future.
“When we look at joint pain, it’s a feedback loop,” says Dr. Beau Whitaker, a Texas-based sport horse veterinarian and certified equine rehabilitation practitioner through the University of Tennessee.
“In cases where we have arthritis or pain in a joint, it causes a reflex spasm of the muscles around that joint—or the tendons that are connected to the muscles around a joint—which then adjust to position that joint in the greatest comfort.”
To you, that might look like a horse that used to stand straight in the crossties starting to habitually prop a leg in a certain way. In other cases, you might notice that your horse starts jumping crooked, or moves differently than you remember up front or behind. Changes like these can indicate discomfort in a range of locations within a horse’s joints.
Because let’s face it, joints work hard.
“The joint has to carry the horse. It has to be able to weight-load. When you have this animal that weighs 1,000 pounds when it’s standing, that’s a lot of weight,” says Dr. Whitaker.
“When that horse is running or jumping, it’s a whole lot of weight. So those joints have to be able to take that concussion. They have to be able to shock-absorb, and they have to stay stable, as well, because you don’t want those joints or bones shearing as the horse moves.”
The good news? While there are many things that can go wrong in a joint, there are also many proven treatment options that can help to relieve soreness, promote healing in injuries or after surgery, and repair damage.
In an April webinar presented by Hilltop Bio, Dr. Whitaker broke down the anatomy and function of the joint, discussed the reasons why they can become painful, and examined the different types of joint injections available, including orthobiologics such as Strydaflex.
Why do horses have joint issues?
In a perfect world, a horse’s joints would always function properly. Joints are essentially a place in the body where two bones come together, joined by an articular capsule, which contains the joint cavity and fluid, encased by a membrane.
Cartilage attaches to each end of bone, as do the tendons and ligaments that stabilize the joint, preventing it from moving side to side or front to back. Joints also include extensor and flexor muscles, which attach to the tendons, allowing for motion.
“We have this intricate play of the muscles on one side contracting at the same time as the muscles on the other side relax,” Dr. Whitaker explains.
Of course, horses being horses, things can go wrong in any or all of these structures, and according to Dr. Whitaker, there’s a long list of reasons why horses may need joint injections.
Among these are horses with developmental or genetic joint disorders, such as osteochondritis dissecans (or OCD), or with systematic inflammation or autoimmune conditions. Horses with hypermobility—the kind of big, elastic movers often prized in disciplines such as dressage—are vulnerable to both joint issues and suspensory problems. Mechanical problems in the joints can also stem from conformation issues or malalignment; for example, a horse that’s pigeon-toed.
Acute injury is still another cause. Trauma to the bone, cartilage, or the soft tissue surrounding the joint can all result in inflammation and pain.
And then there’s age—”any of us over 35 can relate!”—and routine wear and tear (i.e. mechanical stress) on the joints, sometimes caused by working too hard, but often simply a result of overuse based on a horse’s discipline.
“Jumpers are more prone to having some fetlock issues versus dressage horses, which are more prone to stifle issues, because they’ve got so much weight on their back-ends,” says Dr. Whitaker.
A Vicious Cycle
What many horse owners don’t understand is that joint damage can begin long before a horse hobbles off from a flexion exam. Any kind of injury, disease process, or motion that causes repeated, low-grade inflammation, when left to its own devices, can ultimately develop into osteoarthritis.
Here’s how: repeated cell damage in the cartilage signals to other cells in the joint that something is wrong. This causes the release of proteins and proteases, which are then detected by immune cells in the body known as macrophages.
The problem? Macrophages are kind of the Frozen Elsa-character cells of the body; they’re well intentioned, but often create additional problems. Instead of accidentally shooting magic ice bombs from their hands, however, macrophages release additional proteins known as cytokines. Some of these cytokines are helpful and anti-inflammatory (yay!), but others actually cause inflammation in the cartilage (no bueno).
“The best way to intervene on osteoarthritis is to interrupt this cellular communication, or at least steer it in the direction we want it to go. A lot of the new research is looking at macrophages and the role that they play in osteoarthritis,” explains Dr. Whitaker.
“The problem with that, sometimes, is that there’s already this cycle going on before we are able to intervene. And so, by the time we do, there’s already permanent damage that we can’t reverse.”
Orthobiologic vs. Corticosteroid Injections
Joint injections are typically a veterinarian’s first line of defense when it comes to intervening on osteoarthritis. For most sport horse veterinarians, the two most common injection options on the table fall into the categories of orthobiologics and/or corticosteroids.
“As long as we’ve been treating horse joints, we’ve been putting steroids in them,” says Dr. Whitaker.
There are good reasons for that. In addition to their longstanding position in the veterinary medicine cabinet, corticosteroids are typically more fast-acting than orthobiologics. For a horse that has severe inflammation, or is in need of immediate relief, they are often the most effective option.
Orthobiologics, on the other hand—which include regenerative treatments such as PRP, IRAP, ProStride, and stem cells—offer their own unique benefits. Derived from either the patient-horse itself, or a donor, orthobiologics can be used on horses with metabolic issues (think: Cushing’s Disease or PPID) and pregnant mares. They also require less drug-testing withdrawal time for competition horses.
What’s the right injectable for your horse should be determined on a case-by-case basis with your veterinarian. Some vets may use corticosteroids in combination with orthobiologics, or—as Dr. Whitaker often does—inject different types of orthobiologics a few weeks apart from one another.
“Number one [when choosing an injectable product] is it has to be safe, and ‘safe’ means we’re going to cause no harm,” says Dr. Whitaker, adding that inflammatory flare reactions as well as infections are top concerns.
“Number two, we want it to be effective—how long does it help? And how quickly is it going to start helping?” he says. “There’s a broad spectrum of joint damage that we can treat, and we’ll use different products based on the severity.”
Exosomes & Strydaflex
Tackling the osteoarthritic cycle often requires a multi-faceted approach. Strydaflex, a new orthobiologic injectable, is a multifaceted product. One vial of Strydaflex, in fact, contains anti-inflammatory cytokines and IRAP, both helpful in counteracting those ‘bad’ inflammatory cytokines.
Then there’s the exosomes: 3.5 billion exosomes, to be exact.
In short, exosomes are a kind of “messenger” capsule, created and released naturally from cells, and containing a bunch of good stuff for the joints. According to Dr. Whitaker, that ‘good stuff’ includes proteins, peptides, lipids, and nucleic acids, as well as more than six different types of RNA (genetic material). In other words, the osteoarthritis Avenger squad.
“I think of exosomes like a carrier pigeon and a message in one,” says Dr. Whitaker, noting that the exosomes released in Strydaflex are programmed to travel to certain sites in the joint. “They get to that site, that cell recognizes them and pulls them in. Once the RNA is in there, it tells that cell, ‘okay, produce this,’ or, ‘quit producing that.’”
In other words, stop producing those inflammatory proteins that cause joint damage over time.
Dr. Whitaker adds that Strydaflex is also safe and effective, lasting—by his estimation—anywhere from six months to a year in the horses he’s treated. “It really is my first line of defense if I have a horse with a joint injury,” he says.
Dr. Whitaker adds that Strydaflex can also be a good option to assist with the healing process of post-surgical cases and, thanks to its regenerative properties, for the treatment of younger horses as well.
“I wish all my clients had a long-term view of joint health,” he says. “We know that exosomes can have a protective effect in the cartilage and also slow down the progression of arthritis in those joints.
“For clients that want to have their horse around for the next 10 years, I think Strydaflex is a great product.”
Learn more about Strydaflex at hilltopbio.com and speak with your veterinarian to find out if Strydaflex is right for your horse.
