Causes of and Treatments for Soft Tissue Injury in Horses

Has your horse gone lame after a slip or stumble? There’s a pretty good chance he’s hurt a ligament or tendon in his leg. Soft tissue leg injuries are the most common cause of equine lameness. Unfortunately, they also usually take a long time to heal and are frustratingly susceptible to re-injury.

“Horses have highly developed tendons and ligaments, which allows them to have the athletic function that they do,” explained Dr. Melanie Tuplin, an associate veterinarian at Delaney Veterinary Services in Sherwood Park, Alberta. After her 2017 graduation from the University of Calgary Faculty of Veterinary Medicine, she interned at Virginia Equine Imaging where she focused on sports medicine and imaging.

Tendons connect muscle to bone and work as “biological springs” by absorbing and releasing elastic energy as the horse takes a stride, said Dr. Tuplin. Ligaments attach bone to bone and essentially stabilize joints.

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Both tendons and ligaments are primarily composed of parallel bundles of a strong, dense connective tissue called collagen. Despite flexibility and an ability to withstand great force, these fibres have breaking points. When stretched beyond their capacity – usually due to a combination of exercise and age – the collagen bundles tear.

“Typically, injury occurs with fast movement. It is often a combination of fatigue, overextension of a limb, compounded with bad footing, with poor conditioning of the horse and/or continued work in the face of previous injury to the tendon or ligament,” she said. “The strength of the tendon is in the multiple bundles, so disruption or swelling significantly decreases the strength of the structure. The tear causes an inflammatory process, which tends to continue to damage the fibres around the area.”

A horse carries about 60 to 65 per cent of its weight on its forehand, therefore, the tendons and ligaments of the front legs tend to suffer injury more often than the hind legs. Although any tendons or ligaments in the limbs can be damaged, those that perform the majority of biomechanical work are more at risk.

The superficial digital flexor tendon, is particularly vulnerable. A long cable-like structure, it runs down the back of the leg from above the knee (or hock in the hind) and connects the short pastern and coffin bones. It’s mainly responsible for flexing the lower leg. A bowed tendon, with its tell-tale outward curved swelling at the rear of a front leg is, in fact, a torn superficial digital flexor tendon. The underlying deep digital flexor is the runner-up in the damage department. It also serves to flex the leg and provide support, especially to the fetlock.

As for ligaments, the suspensory is the most-often injured. It lies along the back of the cannon bone, originating from just below the knee (or hock) continuing down to the fetlock. The suspensory ligament stabilizes the leg under full weight-bearing load and supports the fetlock.

Treatment for Soft Tissue Injuries

Usually soft tissue injuries trigger heat, swelling and lameness. But not always, warns Dr. Tuplin.

“Sometimes, the horse will simply be lame. Injuries like [those to] hindlimb proximal suspensory ligaments are chronic in nature and bilateral, so instead of an obvious lameness on one limb, the horse will simply have shortened strides behind, which can be very difficult to detect.”

If an owner suspects a soft tissue injury, their immediate goal should be to reduce inflammation, which will help diminish swelling, provide some measure of pain relief and limit tissue damage. Cold hosing the leg works, as does ice therapy – packs, wraps, boots or even simply having the horse stand in a bucket of ice water for a maximum 20 minutes. (See page 44 for more on the RICE protocol used in treating human soft tissue injuries.)

Rest and keeping the horse quiet is also critical in preventing further damage. Standing wraps will support the affected and supporting limbs.

Then a veterinarian needs to assess the horse. “A static exam, combined with a lameness exam is a very important start of diagnosing injuries,” said Dr. Tuplin. “Palpation of tendons, ligaments and joints is important, as well as the lameness exam coupled with flexion [tests].”

Diagnostic analgesia (local nerve blocking) is often used to help diagnose a problem to localize the affected region, she added. The veterinarian will usually ultrasound and/or radiograph the area as well. “Ultrasound should allow for assessment of the size of tendons or ligaments, as well as the fibre pattern that’s present. Radiographs will help assess for bony involvement.”

Further diagnostic imaging can include nuclear scintigraphy, or bone scanning, to provide a “roadmap for complex lamenesses” and magnetic resonance imaging (MRI), which is often used to detect soft tissue injury in the foot and within the hoof capsule, Dr. Tuplin noted.

The course of treatment a veterinarian lays out depends on the injury’s location and severity. The process generally begins with non-steroidal anti-inflammatories (NSAIDs), cold therapy and, most importantly, rest. After heat and swelling dissipate, which may be several weeks later, the veterinarian may suggest some of the newer treatment modalities that can enhance healing and reduce recovery time. These include regenerative therapies such as injections of platelet rich plasma (PRP) or stem cells. “These take cells from the body and amplify the healing cells that we desire and then we inject them back into the affected tissue,” said Dr. Tuplin. “PRP is a product made from the horse’s own blood. The blood is processed in about 20 to 30 minutes and the product can then be injected back into the affected tissue. Stem cells typically need to be harvested and sent to a lab to be grown. This requires more time. Some owners have stem cells harvested prior to injury. They grow the cells and have them stored so that they are ready for when injury occurs.”

Other treatment options include extracorporeal shockwave therapy (ESWT) ultrasound and/or laser therapy. “The accessibility of the newer therapies is often related to the location of the horse and the depth of the pocketbook of the owner. If the horse is located close to a referral hospital, I think most would have the ability to offer these modalities. They often have a decent price tag as they require specialized equipment. However, these modalities may be covered by insurance.”

Surgery may be an option in some instances. Tendon splitting, which involves making small cuts into the damaged area, allows drainage of inflammatory fluid, encourages blood flow and aids in generation of healthy tissue. Inferior and superior check ligament desmotomies are also fairly common procedures. These involve cutting the particular ligament to essentially reduce strain on its associated tendon.

If an owner can’t afford or access regenerative therapies or surgery, rest, cold therapy and controlled exercise – an important part of successful rehabilitation – are, in most cases, enough to yield a successful outcome.

Bringing Horses Back from Soft Tissue Injuries

Movement through controlled exercise not only gets the horse back in shape, but encourages formation of collagen. A veterinarian should oversee any back-to-work regime, which will begin with a few minutes of hand-walking and gradually building up the duration and intensity until the horse can be ridden. Once under saddle, workouts will, again, be low impact with an incremental increase in length and difficulty. Turn out during this time should also be limited and monitored.

Dr. Tuplin said it can be difficult managing horses that had been in intense physical training before being sidelined. “Handling them can be very challenging when they are on reduced exercise. Have experienced people handle the horses and ensure that the people and horse remain safe. Often sedation is required for success.”

She suggested that owners consider sending their horse to a rehabilitation centre if they don’t have the facilities, time or patience to bring the horse back into work slowly and safely. These facilities provide full-service care and treatment for injured horses – at a cost, of course.

Dr. Tuplin stressed that the recovery process can take a year or more. “It will take time. Please be patient.”

And even then, problems often reoccur. “Bone healing lays down thick bone material and tends to be stronger then is was prior to injury. Tendons and ligaments, however, lay down material that is not quite as flexible. The lack of flexibility tends to allow the neighbouring tissue to break down if the area is stressed.”

Preventing Soft Tissue Injuries

What can horse owners do to mitigate the risk of these types of problems occurring in the first place? Dr. Tuplin said proper conditioning for the type of work you want your horse to do is critical. Bring a horse slowly into shape over several months and, “If you want a horse that can go out on the weekend and perform well, it’s important that you also condition them during the week.”

Other precautions include: proper workout warm ups and cool downs; avoiding footing that’s uneven, too hard, too slippery or too deep; avoiding equine obesity; providing regular hoof trimming and shoeing; and post-workout cold hosing or icing to encourage the constriction of blood vessels

However, probably the most vital prevention practice is simply knowing what’s normal for poor Gimpy because early intervention can thwart injuries before they become too serious. Check his legs daily, feeling for heat, swelling or pain that can indicate a soft tissue issue problem. Also be aware of any odd missteps or behaviours.

“Careful attention toward any changes in performance can be great indicators that your horse is uncomfortable and that it may be time to visit your veterinarian,” said Dr. Tuplin.