Last Updated on February 23, 2022 by Allison Price
Thanks to technological advances, it is now easier than ever to diagnose and treat injuries in this complicated joint of the horse.
Horse stifles are something you have been hearing more of lately. In recent years, researchers, joint specialists, and field veterinarians have been paying more attention to the hind limb joint. It is one of the most complex and largest in horses’ entire body. The “it” joint is the stifle, and for good reason.The stifle is one of the most important and complex parts of the horse’s body and has received increased attention from researchers, joint experts, and front-line veterinarians in recent years.
According to David Frisbie (DVM, PhD), “It’s now easier than ever to diagnose and treat problems in the stifle with advances in imaging technology.” “Until about 10 years ago, nobody bothered to treat stifles. You didn’t have many options unless you were a surgeon willing to look inside and open the wounds.
However, stifles don’t seem nearly as frustrating now. Gary Baxter, VMD and MS of the University of Georgia, says, “We’ve just become so much better at handling them.” “And as such, more veterinarians have been willing to look for them. Although you may have heard more about stifle limbiness lately, it is not because there are more horses with stifle injuries. We are more able to diagnose and treat the problem. These horses used to have an “unknown” lameness.
These advancements in diagnosis and treatment techniques can be self-perpetuating, as they encourage and allow curious researchers to continue learning. Frisbie says, “It might sound silly but the stifle can be exciting.” “We have so much knowledge about the other joints, they are boring and repetitive now. When things get boring and repetitive, we move on to our next big adventure. Currently, for veterinarians and surgeons such as myself, that’s the stifle.
Sum of all the parts
Horsemen often refer to the stifle joint as a single joint. However, it is actually three-for-one with many extras. Although it can be difficult to understand the anatomy of the stifle joint, it is essential for diagnosing and treating any problems it may present.
The stifle, which is where the tibia (bone that forms the gaskin) meets the femur (bone that extends upwards to the hip), is called the stifle. The stifle can be compared to the human knee. When you pick up the hind leg of a horse, the joint moves forward just like your knee when you climb a staircase.
You’ll be able to see that the bones are more complex than you might think. A large cleft, also known as a “septum”, is located at the lower end the femur and the upper end the tibia. The junction is characterized by two distinct joints created by this cleft. The joints are located right next to one another and flex in the exact same direction, making them appear to be one. The “medial Femoral Tibial Joint” is the innermost, while the “lateral Femoral Tibiaal Joint” is the outer.
A structure known as a meniscus is found in the femoral and tibial joint – there are two menisci per stifle. Baxter says these thick pads of fibrocartilage, which are much stronger than regular cartilage, are “much more durable than regular cartilage.” They are “much more like a mixture of cartilage and ligament tissue together.” Menisci distribute the horse’s bodyweight throughout the joint and reduce friction when the horse moves.
Frisbie explains that each meniscus is shaped like a teacup. The teacup’s bottom sits on the tibia, while the cup’s rounded end rests inside. The meniscus keeps the femur in its place and allows it to glide when the joint flexes. It’s similar to the role of ball bearings as mechanics.
The patella joint, which is analogue to the human kneecap, and the bottom bone of the foemur bone form the third joint of the Stifle. Baxter says that the patella joint is the ‘front’ of the stifle and the femoral-tibial joints are the two behind’.A horse’s job description greatly influences his risk of stifle injury. Disciplines where you see more sideways motion, like cutting or barrel racing, will have more stifle injuries.
Although the patella joint doesn’t move very much, it allows the shield-shaped bone above the femur to “float”, protecting it and acting as an anchor point. The medial patellar joint runs along the joint’s inside; the middle patellar joint runs down the side of the joint and the lateral patellar joint is on its outside. These ligaments connect the patella to tibia (lower bone of the spine), and the “lateral patellar ligament” is on the outside. You’re probably familiar with “sticking” or locking stifles. Technically, this is called “upward fixation the patella”. This arrangement of bones and ligaments is complex and delicate.
The medial and the lateral collateral ligaments, which are two other thick, short ligaments join the femur bones and the tibia bones at the outside edges. The anterior and posteriorcruciate ligaments are two more ligaments that are buried in the cleft. These ligaments help stabilize the joint while the horse is working.
This complex area of the horse’s body is made up of bones, ligaments, menisci, fluids, and cartilage. Baxter says that the stifle “is a very mobile, weight-bearing joints.” It is composed of many components that must all work seamlessly together with every stride. Musculoskeletally, the shoulder is the only other area that could be as complicated.
The stifle joints are designed to move in a restricted manner. Problems arise when the joint moves in any other direction. Frisbie says that the geometry and anatomy of the stifle joint are designed to allow for movement backwards and forwards. You can get both acute and chronic injuries if things move sideways or twist.
The job description of horses can greatly impact their risk of suffering stifle injuries. Frisbie says that disciplines with more sideways motion (like cutting) will be more susceptible to stifle injury. Horses who jump a lot can sustain stifle injury from the force involved in pushing up and crossing large fences, especially on slick footing. A demographic paper reported that 40% of horses with stifle issues have event horses. Horses in Western performance disciplines would likely be on par or higher.
However, any horse can injure the stifle. Baxter says that a horse can slip in the paddock and pull a ligament. And years of riding or concussions of any kind can cause arthritis. This is a chronic, long-lasting injury.
It can be difficult for stifle injuries to be detected. Stifle injuries are not as easily detected as hoof abscess and bowed tendon. They don’t have a “tell”, as distinct as a head bob or limp. Frisbie says that you can often see the horse’s weight in their stance and push-off phases of a stride. Frisbie says that horses may “give” or drop in the stifle depending on how much weight they have. But that’s not always true.
He continued, “Just the otherday I saw a horse and the trainer, who was very skilled, said to me that it felt like a stifle issue. “And when the horse moved, I thought, Yep. That looks like a problem.’ But the horse stopped making sound in a different joint. Although there are some guidelines, there is no definitive way to determine if a horse has stifle lameness.
Baxter says that what may appear to be a training or behavior issue could actually be stifle lethargy. He says that there are some stifle issues that show up early in life as the horse is reluctant to work. “I have seen horses younger than my own with hurting stifles who aren’t as willing to turn as fast and as sharply as before.”
A visual exam will be the first step in diagnosing a suspected stifle. Baxter says that acute stifle injuries will often have swelling or effusion. It’s not something that an owner will notice but if you have enough experience and know where to look it can be easily identified.
It doesn’t matter if the injury to the stifle is bone, ligament, meniscus, or any other structure, it will likely be on the inside. Baxter says that this is due to how the horse carries weight across the whole limb. It’s not specific to the stifle. “In general, if you have problems in any joint of the limb (pastern arthritis or bog Spavin in the hock), it’s more likely to be on the medial side.”
A veterinarian may use a numbing agent to “block” a suspected stifle injury after a visual exam, flexion tests, and watching the horse move under saddle. Frisbie says, “Personally I’ll block all 3 joints simultaneously.” “If the horse sounds, then I will use imaging to see closer. If imaging doesn’t show anything, I’ll return to the horse and block each joint in the stifle.
Frisbie explained that the problem with blocking specific joints is that they can “communicate”, so one joint can also affect the others. He says, “It is impossible to be 100% certain that you have isolated the problem to one joint.” “Even if you do a surgical exam, it is not always easy to see the problem.
A veterinarian will use imaging technology to examine the joint after it has been blocked. This can be done using ultrasound, radiographs or both. Baxter says that while radiography can be seen in some areas, ultrasound is more useful for spotting abnormalities. Radiography will only show you bone problems, while ultrasound will show soft tissue.
It is evident how important ultrasound technology has been in the management of stifle injury. Frisbie says that the ability to diagnose stifle injury without surgery is a new phenomenon. “Advancements in ultrasound are responsible for a lot of that.”
If radiographs and ultrasound have been completed, but the veterinarian still needs to see more, arthroscopy may be an option. A small camera attached to flexible tubes is inserted into the joint and transmitted images to a monitor. “You can see quite a bit,” says Baxter. “Artroscopy is the best way to see certain areas of your stifle, such as the cruciate ligaments.
Conventional arthroscopy is considered surgery. This means that the horse must be anesthetized, and incisions left behind to heal. New is needle arthroscopy. This uses a scope the same width as a hypodermic needle. Frisbie says, “I began using this scope to examine stifles around three years ago.” Frisbie says, “Now I can see inside the horses while they’re still standing and see injuries which aren’t visible on radiographs.” This allows us to diagnose horses earlier, and the changes to the joints are much less severe and manageable.
Treating common injuries
A veterinarian can diagnose a stifle fracture using all these diagnostic methods. Baxter says, “It is always better to understand what the problem really is.” Baxter says, “We may not always be capable of fixing it, but we can at least try to solve it.” Here are some possible causes of severe lameness.
Meniscal tears are one of the most common acute injuries to the stifle. They are usually caused by twisting and shearing. Either the meniscus can be torn or the ligament connecting it to the tibia may tear.
Baxter says that the severity of an injury depends on how damaged the meniscus is. A true tear can lead to severe lameness. A little fraying of your meniscus might not be a major problem for lameness.
The severity and outlook of an injury or tear to the meniscus can also be affected by its location. Baxter says that if the tear is located in an area that you can access surgically, it may be possible to debride or suture the affected areas. Baxter says that if the injury is below the condyle of a bone, it may be possible to access it surgically. However, it’s not common for menisci to heal on their own. The prognosis for the horse’s long-term health is not good if the horse has suffered multiple injuries.
Frisbie says that modern stem cell therapy can heal meniscal injuries that would have been impossible just a few years ago. The chance that a horse with a severe or third-degree meniscal tear would return to work after surgery was 6 percent. He says that this number has increased by two to fourfold when stem cell therapy was added to the surgery. Horses with torn or strained ligaments around their stifles are less common than you might think. You hear about professional athletes, especially football players, tearing their cruciate ligaments in one bad play. Frisbie says that the dreaded ACL injury can cause a career to end. Although horses aren’t as likely, they can injure the ligament more severely than humans, and we don’t do contact sports with horses,
Your experience with dogs might not apply to horses: “ACL injuries in dogs can be degenerative with partial tears. However, we have not recognized this type of injury in horses. Baxter says that while it is possible, it’s not common.
Horses can also injure other ligaments, including the collateral ligaments. Baxter says that horses can get their feet caught on something and cause severe traumatic injuries, pulling the ligaments. The collateral ligaments are strong and can be diagnosed with either a physical exam, or an ultrasound if they have been severely injured.
The treatment of ligament injuries in the stifle follows the same procedure as other parts of the body. Frisbie says, “Rest, anti-inflammatory medication and possibly stem cells if we are able to locate and access the affected area.” These are all options we have. If we catch it early enough and the injury isn’t too severe, they may work. The horse won’t look back.”
As with any other joint in your body, arthritis can also develop in the stifle. The first sign of this degenerative disease is subtle lameness and osteophytes on stifle radiographs. Subchondral bone cysts, which are pockets of fluid/soft tissue in the bone beneath the cartilage, can develop in areas that support weight. Baxter says that these cysts are caused by concussive forces. There are many ways to treat these cysts. However, they don’t usually fill in with normal bone. You can have problems if you remove the contents surgically. While some horses are able to do well, others don’t.
You can also treat bone cysts by creating microfractures to stimulate the body’s healing process, injecting steroids into the cyst, or filling the cysts with bone cells or biologics to help it heal. Baxter says that all of these treatments work best when used in younger animals. “Traumatic injuries older than arthritis, such as arthritis, tend to be less responsive.”
As with any joint, injections, supplements, and anti-inflammatory medications can be helpful in controlling arthritis of the stifle. But Baxter isn’t shy about stating the long-term outlook. I think arthritis in the stifle can be difficult. It can be tough in any joint. However, the most difficult area in the horse’s body is the weight-bearing medial femoral-tibial joint. This is where arthritis is most likely to develop. We can inject the stafle as we would any other joint and we do it often. It is less likely that we will get the results we desire.
Baxter says that the prognosis is good for mild and moderate stifle injury if it’s caught early. “Horses are very good at identifying problems with their stifles. It is very rare for horses to experience a serious problem without any obvious signs like swelling or lameness. If we pay close attention, we can spot them quickly.
Frisbie says that early intervention is key to a timely diagnosis. If I had to criticize one thing, it would be that surgeons and vets still don’t work on stifles as a first-line procedure. In the hope that it will work, we tend to rest and inject for six to one year. Problem is, if it doesn’t, then we have an older, more severe injury that makes things more difficult. It is important to diagnose and treat the problem as soon as possible.
The stifle is a frontier that has yet to be explored in the world of equine joints. As curious veterinarians embrace the latest technologies, what was once a daunting proposition–diagnosing and treating injuries to the joint–is becoming achievable, and maybe one day, even routine.
I’m Allison, born and raised in San Diego California, the earliest memory I have with horses was at my grandfather’s farm. I used to sit at the stable as a kid and hang out with my Papa while he was training the horses. When I was invited to watch a horse riding competition, I got so fascinated with riding!