This is an introduction to fetlock injuries in horses and the importance of fetlock health in equine performance.

Injuries to the fetlock joint of the horse continue to be one of the most common injuries in performance horses of all disciplines. The average time out of performance is about 90 days. Sport boots and polo wraps are used to protect them from concussion, but structural injuries are more common than concussion injuries.

Understanding the anatomy, lameness presentation, and injury prevention can save you time and money in the long run.

Anatomy of the Fetlock Joint: Structure and components and Function in horse movement

The fetlock joint in a horse is the joint in the lower leg that absorbs and transfers forces as the horse moves. A horse can have up to 200% of their body weight on a single leg at a time. A joint with a 30 cm circumference absorbing the downward force of a sprint and springing back up against 2000 pounds is just wild.

The fetlock joint is the joint between the cannon bone and the long pastern bone. It is anatomically equivalent to the human knuckle that is closest to the back of your hand, both called the metacarpophalangeal joints.

Just behind the fetlock joint in the horse are two small bones called sesamoid bones. They anchor and correctly position the suspensory ligament. They also create a protective “ditch” for both the superficial and deep flexor tendons to pass through. If a horse experiences concussion to the back of the fetlock, the tendons are not superficial against the skin where they are more susceptible to injury, they’re buried between the two sesamoids.

The suspensory ligament is very strong, very thick, minimally elastic piece of connective tissue that creates a sling-type cradle for the fetlock joint. Like the name suggests, it creates suspension to keep the fetlock from dropping all the way to the ground when the horse's body weight plus force of propulsion is on the joint. The ligament is very deep sitting along the cannon bone, starting at the top of the cannon bone, coursing down to the fetlock to split into a medial branch and a lateral branch. The branches wrap about the fetlock to come back to meet on the front of the leg where they insert on the coffin bone.

Common Types of Fetlock Injuries in Horses

The common types of fetlock injuries are:

Suspensory ligament injuries
Sesamoid fractures
Osteoarthritis
Chip fractures

Injuries to the suspensory ligaments are most common in performance horses. Injuries to suspensory ligaments in the forelimbs are more common in track racing, barrel racing, head horses, jumping, reining, cutting, and bucking stock. The hind limbs are more common in dressage, heel horses, breakaway roping, eventing, and endurance. (PS: if you want to know more about discipline-specific horse care, check out my discipline-specific courses here).

Suspensory injuries are specified to be in on of three parts of the suspensory ligament: the proximal portion, the body, or the branches. The proximal portion is specific to the top third of the suspensory ligament, the middle third is called the body, and the branches are after the ligament splits to medial and lateral branches around either side of the fetlock.

Suspensory desmitis is an incomplete injury to the ligament fibers. It can be difficult to detect because of the slow, gradual onset and some horses never present with a lameness. Heat and swelling may be present and obvious, but not always. It may also come and go.

Sprains to the suspensory ligament typically present suddenly and have more obvious symptoms like heat, swelling, and lameness.

Degenerative suspensory ligament desmitis (DSLD) in horses is more complex than “regular” desmitis. DSLD is progressive, career ending, and often life threatening due to quality of life. Dropped fetlocks that rest in severe hyper-extension are the obvious sign of DSLD. There is still much to be learned about DSLD, but it is believed that the cells that create collagen start to create cartilage instead for an unknown reason. Cartilage is not strong enough to do the job of a suspensory ligament. As more cells become cartilage rather than collagen, the disease progresses and the horse's comfort diminishes. They start to spend more time lying down rather than standing and the fetlock hyper extends more and more.

Osteoarthritis (OA) from long term wear and tear occur in the fetlock joint, but is more commonly seen in the pastern or coffin joints as high and low ring bone, respectively. OA in the fetlock joint can start as thickening in the fibrous cartilage pad and the bony growth will start as the body’s attempt to protect the joint. Radiographs and soundness are often not consistent. The OA on a radiograph can look terrible but the horse presents sound. Horses can also present with minimal OA changes radiographically with severe lameness.

Chip fractures in the fetlock are most common from concussion or trauma. Sesamoid fractures are common in track horses from the speed demands. Chips are sometimes removed and the horse has a long successful career.

Causes of Fetlock Injuries

The most common causes of fetlock injuries are:

Overexertion and repetitive stress
Poor conformation
Improper footing or shoeing
Trauma or accidents

Many fetlock injuries are an accumulation of long term damage. Many horses are started too young, too hard and their bodies cannot tolerate the demand. Overexertion and repetitive stress causes micro traumas in the tissue that result in chronic problems. Poor limb conformation in the shoulder, elbow, and especially the carpus lead to more stress on the front fetlock joint as well. A horse being over at the knee or bench-kneed tend to have the most fetlock injuries.

In the hind limb the hip, stifle, and especially hock conformation compromise the fetlock. A hock angle that is more than 150 degrees is most likely to have suspensory and fetlock injuries.

Poor hoof balance is largely responsible as well. Correct balance is critical.

Poor footing can increase the risk of injury as well, so training your horse on varied terrain will strengthen all of the stabilizing muscles and help with injury prevention.

Trauma or accidents both known and unknown of course result in fetlock injuries too. Horses play in the pasture and freak accidents happen.

At the end of the day, they’re just horses that spend their free time trying to figure out how to hurt themselves.

Symptoms and Diagnosis of Fetlock Injuries in Horses

Here’s how you would diagnose a horse with a fetlock injury and the symptoms they may have. We’ll talk about:

Observable signs of fetlock injury
Veterinary examination techniques
Diagnostic imaging (X-rays, ultrasound, MRI)

Signs of lameness may be observable signs such as joint swelling, limping, and heat to the touch, or symptoms as subtle as a personality or performance change.

It's up to you and your team of professionals to be very familiar with their normal so that detecting abnormalities is easier. Regular lameness evals with a vet, regular gait evals with the farrier, and regularly having your hands on your horse will all serve you in determining a diagnosis and treatment plan.

Veterinary examination techniques can include a lameness evaluation, flexion tests, nerve blocking, and diagnostic imaging such as radiography or ultrasound to get an accurate diagnosis and location of the injury.

Treatment Options for Fetlock Injuries

The treatment options for fetlock injuries are:

Rest and immobilization
Anti-inflammatory medications
Physical therapy and rehabilitation
Surgical interventions
Regenerative therapies (stem cells, PRP)

Treatment options depend on the severity of the injury. Rest and immobilization can be critical because of the extreme force the fetlock transfers with movement. It is not uncommon for a horse to need to be stalled or rested for six months to a year.

Cold therapies are simple and effective. There are boots and wraps made for ice therapy, but you can also fill fly boots with ice or cold hose your horse’s legs.

Anti-inflammatory medication such as Equioxx or Bute may help with pain management. Herbal options such as turmeric or devil’s claw may help as well. Corticosteroids can be injected into the joint for pain and inflammation management.

There are an array of options for physical therapy (PT), rehabilitation, and therapeutic modalities. PEMF, lasers, acuscope/myopulse, and red light therapy can all be an essential component depending on what the injury is (ie soft tissue vs bone).

After the horse is released to participate in controlled movement, targeted strengthening exercises will allow the horse to create stability and improve proprioception that will protect the injured fetlock in the rehab process.

Regenerative therapies such as platelet rich plasma, stem cell injections, and Renovo are showing promising results as well.

There are surgical interventions that may be needed to remove a bone chip or repair soft tissue.

Prevention Strategies

Proper training and conditioning
Regular hoof care and shoeing
Appropriate footing and surfaces
Nutritional support for joint health

Strategies to prevent fetlock injuries are easier to do than rehab an already injured horse. Proper training and conditioning strengthens their body to be able to withstand the physical demands of performance.

Regular hoof care and balanced feet will support the conditioning and protect from improper joint mechanics.

Training on irregular terrain and surfaces strengthens small stabilizing muscles that will protect the joint capsule from sudden injury from a misstep or unexpected poor ground.

Correct nutrition will support their whole body and connective tissue. Ensuring they are on an anti-inflammatory diet that balances the minerals in their hay specific to their location will give them stronger tissue that is more resilient to injury.

Prognosis and Recovery

Factors affecting healing time
Return to work considerations
Long-term management of affected horses

So what does real time recovery actually look like? I know we all hate this answer but it genuinely depends. Small fiber damage caught early is way different than a trauma that involves the full width of a suspensory ligament.

The significance of the fetlock (again) is that it is literally catching the entire horse and all their force to spring them forward, sometimes up to 2400 pounds of force at a time.

Early detection, adherence to the treatment plan, and nutrition will result in better long term results.

Make sure the horse is ready to return to work. Completion of a stall rest assignment does not mean return to work. The horse must be rehabbed with target exercises and them conditioned as appropriate under supervision and regular check-ins with the damaged tissue.

Long term management may mean more intentional training and less competition.