The severity of a bowed tendon depends partially on how overloaded it was when it was hurt. Sue Stuska Photo.

Problems with tendons and ligaments are among the most feared of equine injuries. They can, of course, cause the horse to be permanently retired, but even a small injury will mean a prolonged healing period. Plus, once injured, the tendons and ligaments in a horse may never regain their original strength. While there are always some horses that beat the odds, high-performance horses may not be able to return to the same type of work or may have to compete at lower levels after a tendon or ligament injury.

What Happens
When a tendon or ligament is stretched beyond its limits, it will tear. The smaller, weaker bundles give way first. In fact, at a low level, this process is going on during training programs without causing any clinical signs or pain.  This “micro-damage” stimulates the tendon to repair and remodel to a stronger structure. If the work level is increased too quickly during this remodeling period, the horse may be left with areas that are weak and not properly strengthened, or the tendon/ligament may proceed to further damage that results in the obvious clinical symptoms/signs of heat, swelling and pain.

The severity of the injury depends in part on how overloaded the tendon/ligament was.  However, the extent of the injury, and how much of the tendons and ligaments and surrounding structures it involves, depends to a great extent on how much hemorrhage there is (the “black holes” on ultrasound) and how far the bleeding spreads, both inside the center of the tendons and ligaments and into the sheath and the surrounding tissues.

The presence of blood is what triggers an inflammatory response. The inflammatory response is essential for clean up of damaged tissue, and for the early processes of healing but can also result in injury to normal surrounding tissue and excessive scarring. 

Diagnosis
Experts agree that tendons and ligaments injuries don’t happen overnight.  Most cases are the result of a series of small tears that weaken the tendon or ligament, making it susceptible to more serious damage that finally shows up as hot, swollen, tender tendons and ligaments. Some performance barns go so far as to routinely ultrasound their stock in training to detect any small areas of damage.  The observant rider and/or trainer will usually be able to pick up that something is bothering the horse before heat and swelling are obvious. 

Even if the problem is missed until the tendon/ligament swelling is obvious, it’s always advisable to have an ultrasound examination done so that the location and extent of the injury can be seen, and this information used to guide the level of exercise during the recovery period.

Put It To Use • Watch for early signs that indicate tears. • Get an ultrasound examination of the area. • Use ice and compression bandaging. • Administer NSAIDs only as necessary. • Start hand walking the first week.

Treatment And Rehab
As soon as a tendon or ligament injury is recognized, or even suspected, intensive anti-inflammatory therapy in the form of ice and compression from bandaging is indicated.  This is done to limit the degree and spread of hemorrhage because blood in the tissues, even adjacent healthy ones, involves them in the inflammatory and scar tissue process. There’s conflicting information in the research literature about the effects of NSAIDs (e.g., phenylbutazone, flunixin, bute and Banamine) on tendon and ligament healing, and none of it specifically related to horses.  Most vets still choose to use these drugs, although it’s probably wise to limit use to the shortest time period possible and only when obviously needed for relief of severe pain.  Intensive icing actually produces the best anti-inflammatory effect.

The days of stall resting horses with tendons and ligaments injuries is over. It’s now known that early resumption of carefully controlled exercise helps regenerating fibers line up correctly so that the healed tendon or ligament has the best possible strength. Dr. Andris Kaneps, equine sports medicine specialist at Ohio State, describes the following as a typical exercise protocol:
• Weeks 1-8: 10-15 minutes hand walking daily; no free exercise.
• Weeks 8-12: 20 minutes walking twice daily, may ride at a walk; no free exercise.
• Weeks 12-16: 30 minutes walking twice daily, short periods at trot; no free exercise.
• Weeks 16-20: 40 minutes walking and trotting twice daily; increase trot 5 min every 2 weeks; no free exercise.
• Weeks 20-36: Total of 90 minutes walking and trotting; may turn out for free exercise.

During this time, the horse should have an ultrasound examination at least every 60 days. If any problem with increased pain, swelling or tenderness develops, resume icing and bandaging.  The horse should be dropped back to the previous level of exercise and an ultrasound exam scheduled as soon as possible.  The horse will be cleared for return to more strenuous exercise—cantering/galloping, jumping, extended gaits, etc.—only after the tendons and ligaments have completely healed on ultrasound. Even then, work must be resumed carefully.

A variety of other therapeutics have been used, as noted on page 19, but the cornerstones of treatment remain:
• Ice and compression of new injuries.
• Early resumption of controlled exercise.
• Adequate time to allow healing and remodeling.
• Serial ultrasound examinations to document healing and remodeling.

Tendons And Blood Supply Poor blood supply has been blamed for the slow rate of healing of tendons and ligaments. However, while it’s true that blood vessels inside tendons are small, recent research has found that the oxygen levels inside tendons are as good as they are in muscles, and the blood supply plays an integral part in supporting the remodeling and healing process, just like in any other tissue.  In fact, the “black holes” seen on ultrasound of damaged tendons and ligaments are actually hematomas, blood-filled cavities. Feeding During Recovery The last thing the damaged tendons and ligaments needs is to be carrying around a lot of excess weight.  Horses that are overweight should be put on a sensible reducing diet.  Horses of normal weight should not be allowed to gain. For most horses this means a diet with little, if any, grain. Some tips:        • Consult with your local agricultural extension agent or state university to find typical protein and mineral levels for your hay type or, better yet, have it analyzed. • Substitute small amounts of alfalfa (if your hay protein is low) or grass hay pellets, or a high-fiber, low-fat complete feed, or a reduced-calorie, mineral-rich feed for the usual grain feeding. • Add the essential amino acids lysine and methionine if your vet/nutritionist advises. Typical feeding levels of these are 5 to 7 grams/day of lysine, 2 to 3 grams/day of methionine. • Consider supplemental vitamin C, 5 to 7 grams/day, for horses that don’t have access to fresh grass. • Be sure to supply a mineral supplement that complements the trace mineral profile of your hay to ensure adequate and balanced intakes of copper and zinc.

Risk Factors
While “bad steps” get blamed for the majority of tendon and ligament injuries, and certainly do account for some, most tendon and ligament injuries are due to a combination of inadequate conditioning, including inadequate time allowed for the tissues of a horse in training to adapt, and the strain the work puts on them.

• Horses doing galloping work and landing after jumps load the superficial digital flexor tendon first, increasing risk of bows.

• Horses working at speed often load the suspensory digital flexor tendon to 16% of its capacity.  Injury can occur between 12 to 20% of stretch, equivalent to loads of 2.5 times the horse’s body weight.

• Racing Standardbreds, horses working in an extended trot, and some gaited horses load the suspensory ligament first and have more suspensory problems.

• The ability of tendons and ligaments to withstand high stresses decreases with age.

Common Injuries
When a horse is lame or even just feels “off” and there is no obvious heat or swelling to pinpoint the cause, two of the most likely problems are foot pain or early tendon/ligament injury. Never continue to work a horse like this, and never just give anti-inflammatories hoping it will go away. Get a good lameness vet in for an exam, blocking the feet, and if the problem remains go to ultrasound of the tendons and ligaments, including at their origins and insertions.

The most common types of injury in horses are “bowed tendons” and suspensory ligament tears. Bows are most often found in the center of the superficial digital flexor tendon, the tendon closest to the skin, running along the back of the lower leg.  The suspensory ligament runs underneath the flexor tendons, and behind the cannon bone.  It can be torn anywhere along its length, from the attachment at the top of the cannon (“high” suspensory), in the middle of the body, or along one of the branches that attach to the sesamoid bones (“low” suspensory).

Prevention       
Foals and yearlings should not be stall-confined.  Studies have shown this greatly decreases the normal maturation of tendon and ligament tissues.  Youngsters kept in part of the day and turned out the rest of the time have the highest risk of tendon and ligament injuries because their pent-up energy leads them to play too hard and injure themselves.      

Young horses, late yearlings and 2-year-olds can benefit greatly from a low-level, slow, progressive, formal exercise program because their tendons and ligaments have the greatest remodeling capacity at this age.

A solid conditioning program should take a minimum of four to six months to gradually bring the horse up to the duration and intensity of work required.  Short cuts in conditioning are most likely to show up as bone and tendons and ligaments injuries.

The tendons and ligaments of a horse in work should be palpated every day, religiously. Any filling, heat, sensitivity is a red flag to begin icing, decrease work and ideally get an ultrasound examination done immediately.

Prognosis
As you might imagine, the prognosis for a horse returning to his previous level of work after a tendon/ligament injury has a great deal to do with what that work was.  For example, in a large study that was condicted in the United Kingdom, show jumpers had a better chance of returning to their sport than event horses, and event horses a better chance than racehorses (flat racing and steeplechase). 

The best predictor of risk of re-injury in that study was the fiber alignment score.  Horses with a large percentage of the new fibers in the injured area lined up correctly in parallel rows have a lower risk of re-injury than those whose fibers are not well-aligned.