The Equine Stifle Joint

Your horse’s stifle joint, the joint directly above the hock joint on the hind leg, is the largest joint in the horse’s body. Comparatively speaking, it’s the knee joint of the horse. The equine stifle joint has many functions and, therefore, many opportunities to develop problems. Lets also dig into some common stifle problems in horses and what you can do about them.

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Jobs of the stifle

The stifle joint functions to flex and extend the hind leg, moving your horse along.

This joint is also part of the passive stay apparatus that locks your horse’s hind leg while resting. The other hind leg will be lowered for rest and relaxation.

When comparing anatomy to the human skeleton, the stifle joint is equivalent to the knee. However, the human knee is straight when we are standing, and the stifle is angled when the horse stands.

Like other species’ knees, the horse’s stifle is a complex joint, complete with a knee cap – the patella.

The horse’s head is to the left on this skeleton.

Horse anatomy of the stifle joint

Surrounding structures of the stifle include bones, muscles, and soft tissues. Above the stifle is the femur bone, below the stifle is the tibia, and the patella knee cap sits towards the front of the stifle joint.

Inside the stifle joint, there are two femorotibial joint cavities. Within each of these joint cavities, you also have a medial and lateral compartment. Also, within the stifle joint, you will find menisci (articular cartilage) between the femur and the tibia bones. There are also two cruciate ligaments within the femorotibial joint that help the stifle remain stable. On either side of the leg, your horse has collateral ligaments.

The quadriceps femoris muscle and the femoropatellar ligament keep the patella (knee cap) in place. The quadriceps muscles are above the patella. The patella is also supported by three patellar ligaments below it.

Stifle issues in young horses

With such complicated anatomy and the general propensity for horses to suffer traumatic injury, there are many potential problems that can lead to stifling lameness. In young horses, a few things are more common as a horse grows.

Younger horses may also develop osteochondrosis. This is a general term that describes the unusual development of cartilage in a joint. Osteochondritis dissecans (OCD) is a development from osteochondrosis that happens as the cartilage and bone separate. This may result in cysts and bone chips. Treatment options can be medical or surgical and depend on many factors, from age to severity to overall health and outlook.

Bone cysts are odd developments, occurring in the stifle and sometimes the fetlock. The cause is often unknown but may be related to OCD or a mystery injury. Commonly seen in young racehorses, the cysts will create lameness without noticeable joint swelling. Some horses do well with rest and anti-inflammatory medications, while others need joint injections or surgery.

The locking kneecap

And upward fixation of the patella can happen. This occurs when the kneecap sticks along the femur and the joint can’t flex. Maybe this happens totally, and the joint is locked, or it can be partially luxated, and you hear a popping sound. Horses with legs that resemble straight lines are more likely to have this. Certainly, genetics plays a factor here, although some horses, after time off from another injury, can develop this, likely due to decreased muscle mass.

If the joint creates a locked stifle, you will see a horse dragging that leg behind. Talk to your vet pronto if you see this, it might need to be popped back in place. Your vet may have you back up your horse or ask them to walk with a direction change over that stuck leg. Your vet may have to pop it back manually.

Sometimes, horse physical therapy successfully reduces this occurrence by building up the quadriceps and hind-end muscles. Quite often, strengthening those thigh muscles is enough to keep the patella in it’s home.

The hind legs hold a lot of power and mobility.

Stifle problems in horses and stifle joint injury

While the previous problems typically affect younger horses, horses of all ages can have any common stifle disorder, which may lead to severe lameness, but we certainly hope not.

There is a rare patellar luxation that pops out of place to the side. Usually, a horse isn’t in pain but will perhaps stand funny. Veterinary surgery is usually the best treatment.

Gonitis is when the equine stifle joint is inflamed due to osteochondrosis, patellar luxation, injury, arthritis, infection, or many other things that horses do to themselves. Often, you and your vet will have no idea why this happens, but you have noticed that the hind leg doesn’t step under your horse as well, or your horse has a new and strange way of standing. With the various causes of gonitis, it will take some veterinary detective work to find the soft tissue inflammation cause and create a good treatment plan. This can be anything from conservative treatment to retirement, maybe surgery. Every case is different.

Like other joints, the stifle can develop degenerative joint disease (DJD). This DJD usually starts with arthritis and ligament injuries. There is often not an exact cause, but for therapeutic purposes, it’s best to consult your vet for a good plan of action.

The mystery stifle injury on a horse

Horses can also have stifle injuries involving the bone, such as a fracture or a tear in the soft tissues (ligaments, tendons, and muscles). Kicks to the stifle are often the culprit here, as are running and jumping. Long-term repetitive stress, as well as acute injuries, can damage the stifle joint and surrounding tissues, and both English and Western performance horses suffer from these wear and tear situations. Disciplines that tax the hind end can be a problem down the road.

There is also the case of a horse that finds himself tangled in the fence or has a cut or puncture near the stifle joint. Infection is a real threat and can permanently damage the stifle joint. Really, any cut or wound can become infected, and when this happens over a joint, things can go sideways in a bad way quickly. Sometimes, the severity of the injury influences the therapy plan, sometimes not. Simple wounds on a horse’s leg can end up as cellulitis, whereas giant injuries are easy to treat quickly.

And the hind legs can really tuck up!

Watch your horse – signs of a sore stifle

Your daily grooming routine should include using your hands and eyes to cover every single inch of your horse! Feel for heat, swelling, tenderness, cuts, scrapes, or anything unusual on the actual joint.

But – you may also find your horse is sore in his back – specifically the croup and loins (loins are directly behind the saddle, keep going to the tail for the croup). Hind leg problems are often transmitted to your horse’s back.

On the ground – do you notice if it’s harder for him to pick up one hind leg? What about turning around in his stall, is it easier in one direction than the other? What about how his hoofs track up when he walks next to you? Does one hind hoof overtrack the front when the other hind hoof doesn’t overtrack at all?

Stifle issues also show up as lameness. For a rider, the canter is the gait where you will feel and see trouble. Cantering on one lead is harder, picking up the canter is difficult, and shifting from trot to canter is hard. Also consider “cross-firing”, the case where your horse will have the correct lead in the front but the wrong lead behind. Bending is also tricky.

If your horse is post-legged, his stifles are more susceptible to problems.

Stifles often need supportive care. Just like any athlete!

Help keep your horse’s stifles in tip-top shape

Support your horse’s joint health with daily care. Lots of attentive grooming can help you spot problems before you go riding.

Give your horse plenty of appropriate and relaxed warm-up. Not many seasoned horses can go from grooming to trotting around without significant walking. Avoid sudden stops, sharp turns, bad footing, and abrupt movements as you ride. Also, mind the canter transitions and cross-firing.

Give your horse loads of turnout and movement.

Have your vet involved in your horse’s joint care. Ask your vet for flexion tests during routine visits for dental health and vaccinations, especially if your horse’s age, prior injuries, and overall health make them a great risk for stifle problems.

Your farrier may offer corrective shoeing to support the hind limbs.

Support the joint cartilage and movement of the joint with a well-balanced diet, including Omega-3 fatty acids and any number of scientifically studied joint supplements.

Treat the stifles with ice therapy, liniments, and other topical treatments that are easy to do while grooming and after riding to prevent stifle problems in horses.

How can you prevent injuries to the horse’s stifle joint?

To prevent injuries to the equine stifle joint, ensure proper warm-up and cooldown routines before and after exercise. Regularly inspect the stifle joint for any signs of swelling, heat, or discomfort. Maintain a balanced diet and appropriate exercise regimen to support horse joint health.

What exercises can help strengthen the equine stifle joint?

Exercises like controlled backing, hill work, and cavaletti exercises can help strengthen the equine stifle joint. These activities promote muscle development and joint stability, crucial for maintaining optimal stifle joint function in horses.

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