Horse Health TopicsThis is part of a new series on OTTB health exploring common injuries, issues and concerns of interest to prospective Thoroughbred owners. A Disclaimer: Of course we’re not veterinarians; we urge you to speak with a qualified professional about the prognosis of the particular horse that you are considering. |
Bowed Tendons, A Definition:
A “bowed” tendon is named for the bow shape the back side of the lower limb (usually the front) develops because of swelling in the tendon. There are two tendons that run down the back of the leg. The one nearer the skin and the one that usually “bows” is the superficial digital flexor tendon. The one nearer the cannon bone is the deep digital flexor tendon. The suspensory ligament runs from the knee (or hock) to the ankle, and lies between the deep digital flexor tendon and the cannon bone. It provides support to the ankle during the weight-bearing phase of the stride. — From Dr. Lydia Gray’s SmartPak blog
Note the superficial and deep flexor tendons and supporting ligamentary structures.
What Should I Ask If I See That a Listed Horse Has a Bowed Tendon?
Bowed tendons are one of the injuries that we commonly see when taking CANTER New England listings.
The majority of bows in racehorses are seen are in the front legs; so for the purposes of this discussion, we’ll focus on front leg injuries.
If you’ve looked at the listings and see a tendon injury mentioned you’ll have noted a very critical piece of information: whether it’s a “fresh” or “set” (also called “cold”) bow…that is, did the horse recently sustain the injury, or is it healed and not presenting any current problem for the horse?
If you come to see a listed horse that has a recently bowed tendon you may find that the horse is three-legged lame, or only slightly off. Much depends upon the length of time since the injury, the degree of tearing and tissue damage suffered, the extent to which supporting ligaments and joints are involved and the post-injury care given the horse.
Be sure to ask how and when the injury was suffered:
- Did the horse bow in a race, or was the injury suffered in training?
- Is the injury a primary tendon injury, or did the horse rebow (reinjure) the tendon?
- Did the horse strike the tendon with a back foot?
If the horse did strike a front tendon with a hind foot during a race, or while training, it’s important to note whether or not there is an actual wound associated with the tendon injury.
If the horse actually cut the leg with a hind shoe, you want to understand whether or not the sheath surrounding the tendon was damaged, as infections in this structure can be quite serious.
As a Note: You may see a horse that has a “bandage bow” where there is significant lameness and swelling. A true “bandage bow” does not involve actual tearing of the tendon fibers, but bruising and swelling of the tissues, instead.
How Does a Horse Bow a Tendon?
According to Dr. Greg Andrews, cited in a Grayson Jockey Club article:
“There are various degrees of bowed tendons, from mild tearing that you can hardly detect, to completely torn (severed). The injury can be due to hyper extension of the fetlock joint (putting great stress on the tendons), usually during performance, and often associated with fatigue. When a horse gets tired, his legs have less muscle control; fatigued muscles are no longer working smoothly, and give less support to the leg. The fetlock joint may go clear to the ground as the horse is running.”
When a tendon is overstretched, or “bowed” the fibers of the tendon–which are normally smoothly aligned down the length of the tendon–are disrupted. Because the fibers of the tendon don’t heal back to this original, smooth orientation and due to the formation of scar tissue, the tendon loses some of its elasticity.
Bows may occur at any point along the tendon and you will commonly see the bow described as “high”, “middle” or “low”. A “high” bow may be accompanied by injury to ligaments in the knee; conversely a “low” bow may occur in conjunction with injury to the suspensory ligaments around the fetlock.
When the vet ultrasounds the injury they may find a focal point of damage–a “core lesion”–or scattered damage throughout the tendon structure. Injuries to the superficial flexor tendon are more common, and generally have a better prognosis, than injuries to the deep flexor tendon.
A horse may suffer a tendon strain in training if they are pushed before fit enough, or pushed when they are fatigued. If the horse is not rested at this point, they may suffer a true bow.
How Are Bowed Tendons Treated?
When considering a horse with a bow, the vet may suggest an ultrasound of the leg to determine the degree of tendon damage, and to ascertain if there is involvement of (suspensory and other) ligaments. They may also suggest x-rays to understand if bony structures, such as the horse’s sesamoids, were damaged at the time of the injury.
If you do take on a horse with a tendon injury, your vet will likely want to do periodic ultrasounds in order to check on the progress of healing, suggesting adjustments to the horse’s rehabilitation program based on ultrasound findings.
Care of the horse’s leg after the bow may involve cold hosing for sessions up to 20 minutes in duration, wrapping to offer support to the front legs, and administration of both systemic and topical anti-inflammatory drugs to help relieve pain and swelling.
Other treatments are available, including use of stem cells, bone marrow or plasma injections. Shock wave therapy may be used as an adjunct to other treatments. If the tendon sheath is involved, the vet may suggest the injection of hyaluronic acid.
If you are considering a horse with a bow you should discuss the options with a veterinarian: some treatments are only effective during a specific window of time, post-injury and may vary widely in cost. It may be that the vet will simply suggest continued use of hosing and anti-inflammatories, with a controlled rehabilitation program.
Depending upon the severity and newness of the injury the veterinarian will suggest a specific rehabilitation regimen to ensure that the horse maintains proper circulation in the leg and to minimize adhesions in the healing tendon.
What Is The Long-Term Prognosis for Horses with Bowed Tendons?
Horses with “cold” or “set” bows do sometimes return to racing after the initial injury is healed and compete without suffering any further complications, though they may be less competitive than previously.
However, it may not be economically viable to rehabilitate a lower-level claiming horse and bring it back to racing as it can take 9 – 12 months to fully recover from a tendon injury. In these cases the owner and trainer will often opt to retire a horse, or list it on CANTER New England.
Many horses that do return to the stress of racing after a bow do reinjure the tendon. Whether they suffer a simple strain, or actually rebow the tendon, some of these horses can still be useful in pleasure careers.
What do the experts say about the outlook for a horse with a tendon injury? You can find a great deal of literature on the Internet about the management and rehabilitation of equine tendon injuries. However, since there are many factors to consider in each individual case, it may be difficult to generalize these findings to the specific horse that you are considering.
“Your horse’s prognosis depends on many factors, including the structure involved and the severity and extent of the initial injury. For example, a 20% tear of the deep digital flexor tendon yields a much poorer prognosis than a 20% tear of the superficial digital flexor tendon.
Current and intended use of your horse also plays a role. For example, a Thoroughbred racehorse with a 30% tear of his superficial digital flexor tendon may not return to racing, but could become a successful hunter.” — Dr. William Pritchard, UC Davis
Over the years we have seen many horses with tendon injuries listed through CANTER New England go on to have successful second careers with proper rehabilitation, patient handling and good management.
Management of a horse recovered from a tendon injury includes special attention to:
- Good farrier care, ensuring that toes do not get overly long between trimmings and that the foot hits the ground squarely;
- Sufficient warm-up before any strenuous work;
- Careful attention to fitness so that the horse’s muscles are able to support the tendons and ligaments properly in the work that will be asked of the horse.
The bottom line: many horses with tendon injuries are quite capable of having good second careers, which often includes use as jumping horses. But each injury and horse can present a very different prognosis, so careful evaluation by a veterinarian familiar with OTTBs can help you understand if the horse that you are considering will be physically able to hold up to the job you have in mind.
Here are some references to provide further information:
Wikipedia page on Tendonitis in Horses
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