The first time I saw a horse with a bowed tendon was at the barn where I kept my horse, when a new boarder unloaded her gelding from the trailer. I made some admiring comments, but noticed a slight bulge on the back of his foreleg and had to ask, “What’s wrong with his leg?”

“Nothing now,” she told me. “That’s a bowed tendon, but he’s recovered and back to work.”

“So he’s not lame?”

“Not a bit.” She was telling the truth, as I learned when I watched her riding him over the next few months.

An Occupational Hazard

Dr. Keri Thomas, assistant professor in Large Animal Clinical Services at the Western College of Veterinary Medicine in Saskatoon, SK, explains that a bowed tendon is the result of an injury to the superficial digital flexor tendon (SDFT) or less often, the deep digital flexor tendon (DDFT), which run down the back of the horse’s leg. It could be caused by a single traumatic incident such as stepping into a gopher hole, or it could be the result of repeated stress that gradually damages the collagen fibres that form the tendon.

Some equestrian activities can increase the risk; bowed tendons are seen frequently in racehorses or jumpers, for example. “You see this repeated stress causing damage in horses that have jobs that require high speeds or jumping,” says Thomas. “If you look at photos of horses landing over jumps, the tendons can be really overextended. Barrel racing is another sport where this kind of damage can happen – the horses are really working hard, even though it is just for a matter of seconds.”

The torn fibres within the tendon undergo inflammation, bringing increased blood and inflammatory cells to the area, and the swelling that results gives the tendon that “bowed” appearance. As well, the inner fibres in the tendon are generally damaged first, resulting in a core lesion that can be identified via ultrasound.

At the time of the injury, the horse will often be lame, but Thomas says this is not always the case. The degree of lameness depends on the severity of the injury. Sometimes the lameness is so subtle that it is missed and the injury isn’t noticed until the swelling becomes apparent. More frequently, you can feel heat in the area where the tendon is swollen, but again, in some cases this is not noticeable.

Minimizing the Damage

Whether or not those other symptoms are present, a bowed tendon should be seen promptly by a veterinarian, who will usually do an ultrasound of the leg to confirm the diagnosis. This ultrasound is important as a baseline as well; your vet will follow up with additional ultrasounds as your horse goes through the treatment and rehabilitation process and he or she can assess how well the tendon is healing.

While waiting for the vet to arrive, you can begin initial treatment by moving the horse into a stall or wash bay and hosing the affected leg with cold water, or applying cold compresses followed by bandaging. You may also be advised to give anti-inflammatory medication (such as “bute”). Once the vet has examined the horse, he or she may use a technique called tendon splitting, by inserting a needle or scalpel into the affected area to release some of the blood and inflammatory cells and help reduce the swelling.

A typical bowed tendon. Although unsightly, if caught early and treated vigilantly most horses can return to their previous form. (Photo courtesy Western College of Veterinary Medicine)

With these treatments underway your horse may appear to be sound, but a premature return to exercise will generally lead to increased lameness. A rehabilitation program to heal the tendon is essential (see ‘The Path to Soundness’). “Healing a bowed tendon will take several months at a minimum,” advises Thomas. Your vet will help you develop an individualized plan for your horse that will start with complete rest and gradually increase the level of exercise both in-hand and under saddle. Using ultrasound to monitor the healing allows the vet to check that this rehab program is not moving too quickly or too slowly.

“The collagen that is formed in the tendons during recovery is not as healthy as the original collagen,” explains Thomas. “The original collagen is stretchy and the fibres slide past each other, but the newly-formed collagen is more rigid.” Properly planned exercise helps the new collagen to be more functional, but increasing the level or duration of exercise can lead to more tendon damage. “It’s a fine line we’re walking,” warns Thomas.

Because the newly-formed collagen is not as strong, the horse is now at a higher risk of developing a bowed tendon again. Ensuring your horse is in good condition before asking him to perform more demanding activities can help prevent future problems; you’ll also want to keep up with routine farrier work and pay attention to proper shoeing while avoiding deep mud and uneven ground. With those factors in mind, you should be able to continue to enjoy riding and competing with your horse without any recurrences.

Slow and Steady

Expect months of slow progress – the speed of recovery and prognosis depends in part on the severity of the original damage to the tendon. In many cases, the tendon will look normal after it has healed, but in other cases the tendon will always look thickened or bowed, even if the horse has returned to soundness.

New therapies for bowed tendons are being developed that have shown encouraging results. These include injections of stem cells or platelet-rich plasma to encourage the growth of new cells, or shockwave therapy which is believed to help the collagen fibres line up more effectively. Research is still ongoing; there are also many commercial products touted to cure bowed tendons despite a lack of research to validate their effectiveness.

If the injury isn’t too severe and the rehabilitation program is followed faithfully, Thomas says many horses have the potential to return to the same level of work they were doing before the bowed tendon developed. Those that can’t return to their original career can possibly be switched to a discipline that isn’t quite as demanding.

THE PATH TO SOUNDNESS

Here’s a sample plan that Thomas recommended for one patient with a bowed tendon. Each recovery schedule will be different and may be modified based on information from the ultrasound checks.

First 30 days:

Horse in stall with 15 minutes of hand-walking twice a day.

Days 30-60:

Horse in stall; gradually work up to 40 minutes of hand-walking twice a day.

Days 60-90:

Increase to 60 minutes of hand walking, twice a day. Supervised turnout with hay as a distractor in a small 8m x 8m pen for up to three hours a day, depending on the weather (no deep or muddy footing).

Day 90:

Turnout in small pen (roughly 5m x 11m) for up to eight hours a day.

Days 90-120:

Ride at a walk 30 minutes/day.

Days 120-150:

Work up to 1 hour of ridden walking/day.

Days 150-180:

Add 2 minutes of trot each week, building up to 8 minutes of trot per day by the end of the month.

Days 180-210:

Continue to add more trotting at 2 minutes/week and introduce 2 minutes of canter per week.

Days 210-240:

Continue gradually adding trot and canter by 2 minutes each per week.

Days 240-270:

Resume regular flat work

Days 270-300:

Begin jumping low jumps