Tendon Damage in Horses: Shock Diagnosis- What Now?

Structure & function of the tendon apparatus of the horse

A thick, warm tendon on a horse's leg can be alarming for any rider. Tendon damage is a common issue that affects not only racehorses and high-performance athletes but also recreational horses. To understand how tendon injuries occur, it’s important to first examine the structure and function of the horse's tendon and ligament system.

The horse’s ability to run and jump relies heavily on its tendons and ligaments. Tendons are crucial for transmitting power and consist of fine collagen fibers arranged in orderly bundles. These bundles combine to form the tendon, which is encased by the tendon sheath. Tendon ends are firmly attached to the periosteum and muscles, allowing them to effectively transfer force during movement. Consequently, muscle quality significantly impacts tendon health. Support ligaments further stabilize and support the tendons.

The most important and well-known tendons are the superficial and deep flexor tendons, as well as the pastern tendon. These tendons run along the back of the cannon bone and can be easily palpated when the leg is lifted.

The superficial flexor tendon and the fetlock support are heavily stressed during landing. When a horse lands after a jump, the superficial flexor tendon can absorb up to 200% of the body weight, despite the muscles having already cushioned a significant portion of the impact. The tendon can stretch up to 16% of its length during this process—a remarkable feat.

During landing, the superficial flexor tendon is supported by the fetlock beam and its associated ligament. This tendon bears the majority of the load, making it especially susceptible to overloading. Damage to the fetlock ligament is one of the most common types of tendon injuries in horses.

The deep flexor tendon, on the other hand, is the most heavily loaded during the footing process. It tensions the hoof joint.

The extensor tendon is located at the front of the leg. This is only exposed to low loads, which is why injuries rarely occur here.

Tendon damage in horses often comes as a shock to many owners because tendons and ligaments, which provide stability, are difficult to strengthen compared to muscles. Connective tissues in horses only reach full maturity by around age six, making them capable of supporting their full weight. Additionally, tendons and ligaments have a limited blood supply, which means they receive less oxygen and fewer nutrients, resulting in slower regeneration.

Causes of tendon damage in horses

Tendons are designed for high tensile loads. Their elasticity is nevertheless limited. If the bow is overstretched, individual tendon fibers, tendon bundles or the entire tendon tears (tendon rupture). The fact that tendon damage is a widespread problem in horses is partly due to the lack of protection of the tendon itself: Directly under a thin layer of skin, it is not protected by muscles. The following scenarios can also cause fiber tears and tendon ruptures:

• Acute overload, e.g. incorrect landing after a jump, stumbling
• Too early use in sports
• Cold starts, no warm-up
• Hard turns
• Too little movement due to inappropriate posture
• Muscle fatigue and poor muscle condition
• Unfavorable ground conditions (deep, uneven, hard, slippery)
• Positional defects of the hooves and legs
• Overweight
• Breeding faults: foals too heavy, too little exercise, too early breaking in.
• Change in breeding to "over-striding" horses with soft connective tissue
• Hereditary disposition
• Side effect of other problems, e.g. protective posture due to pain elsewhere
• Blunt trauma from kicks
• Overheating and circulatory disturbance due to inappropriate gaiters and bandages

Symptoms: Recognizing tendon damage in horses

If fiber tears develop in the tendon, blood and lymph fluid enter these areas. The larger the damaged area, the more fluid - the tendon swells. 

• The swollen area is warm
• Pulsation of the fetlock joint is noticeable
• The horse is sensitive to touch
• Varying degrees of lameness after short exertion
• The horse relieves the affected leg a lot or lies down frequently

Differentiation from other diseases of the tendon apparatus

• In tendonitis, only the tendon sheath is affected, the sheath in which the tendon fiber bundles lie. Tendonitis is just as painful for the horse as it is for humans. If the tendon with its tendon sheaths is affected, it is called tendovaginitis. If only the tendon is affected, the medical term is tendinitis.
• In a tendon rupture, the tendon is torn. This mainly affects sport horses and overweight horses that are exposed to extreme loads. A tendon rupture can occur in already damaged structures that had not healed completely. A distinction is made here between chronic rupture (rupture recognized late because there was no lameness) and re-rupture (rupture of the same site).
• Fetlock tendon damage is a common tendon disorder because the fetlock tendon takes a large part of the body load. Its treatment is more complicated than that of the flexor tendons because the pastern tendon lies deep in the leg and is therefore difficult to reach.
• Galls also often occur in the area of the tendons and fetlock joints. However, they are fluid accumulations that usually do not cause pain and rather indicate overstimulation of the joints.

Diagnosis

If you suspect a tendon injury in your horse, you should contact your veterinarian directly. Even for an experienced veterinarian, it can be difficult to locate the origin of the lameness, as not all tendon damage is accompanied by swelling, warmth and lameness.

First, the veterinarian will assess the gait pattern at a walk and trot and the degree of lameness. From this, initial conclusions about the injury can already be drawn. The affected leg is then palpated for circumference, warmth and pressure sensitivity. If the veterinarian is certain that there is tendon damage, an ultrasound may be done to determine the exact extent. If the veterinarian has limited resources, a trip to an equine clinic may be necessary.

Treatment of tendon damage: What to do if the horse has a thick tendon?

The way in which tendon damage is treated in horses varies from horse to horse. This is because the regeneration process is extremely individual:

• Day 0 - 10: In the acute phase, blood and lymphatic fluid enter the fissures, and edema forms.
• Day 4 - 21: The healing phase begins. A transitional tissue is formed, which is not resilient. New injuries can easily form during the phase, so utmost caution is required.
• Day 28 - 120: The tendon fibers gradually arrange themselves and become more resilient. Now the amount of walking can be increased by minutes daily (see training plan for horses after box rest).
• Day 121 - 365: Approximately after one year, the tendon tissue is renewed and healed.

The goal in treating tendon damage in horses is to minimize irreversible structures. For this purpose, there are various therapeutic approaches aimed at achieving elastic structures.

Local Therapies

• Cold therapy: Cold is applied in the acute phase to minimize the spread of bleeding and inflammation. Cold can be applied to the horse's leg with cold water, cooling gaiters or cooling pastes for rubbing.
• Heat therapy: The acute phase is followed by regeneration. Good circulation is important so that inflammatory products are removed more quickly and healing is accelerated. Heat can be done with heat-reflecting gaiters.
• Magnetic field: Magnetic gaiters can stimulate blood circulation.
• Shock wave therapy: Stimulates blood circulation. Has proven effective for chronic tendonitis and pain therapy.

Injection Therapies

Injection therapy involves injecting a healing-promoting agent into the horse's leg that has a positive effect on regeneration. There are various methods for this, for example according to Müller-Wohlfahrt or a bone marrow transplant.

Stem Cell Therapy

Stem cell therapy is increasingly used in the equine world to treat lameness. Stem cells act specifically on damaged structures, which is why this treatment method is considered a milestone in veterinary medicine. In this process, blood is taken from donor horses, processed and "pre-programmed" so that the stem cells adapt to the corresponding tissue. The stem cells are then applied by injection.

‍Laser Therapy

Laser therapy has become established as an adjunctive therapy. It is still relatively new in the field of tendon damage in horses, but has nevertheless proven effective in improving the elasticity of the tissue.

Even though the range of treatment options is wide, the motto is still: be patient and don't rush things. Tendon injuries need time and rest to heal. No therapy option is the panacea for shortening the regeneration process in any way.

Immediate measures: What can I do in the event of tendon damage?

• Cool immediately until the vet arrives. Cooling should only be done in the first days after the injury.
• Immobilization/ box rest: In the acute phase, rest is important to prevent further tearing. Depending on the extent of the tendon damage, either total box rest or controlled exercise at a walk is advised. It is essential to discuss this with the veterinarian!
• Following the acute phase: Heat promotes blood circulation and thus the removal of inflammatory substances. Controlled movement adapted to the state of healing maintains the gliding ability of the tendon and prevents adhesions.
• Step phase: An ultrasound provides information on how much the tendon may be loaded. Particular care must be taken during this sensitive phase, as the fibers can tear again if the strain is applied too early.
• Accompanying regeneration, massages and treatment by a physiotherapist or chiropractor are suitable for maintaining the mobility of the organism and releasing tension.

The right feeding for tendon damage

The right supply of nutrients is just as important for the regeneration of a tendon damage. Nutrients such as magnesium, selenium, manganese and natural vitamin E have a positive effect on tendon health. Pay attention to organic compounds so that they are optimally available for the horse.

Herbs such as rosehip, verbena or tarragon have an anti-inflammatory effect and have long been proven in the regeneration of tendon damage.

If the horse has to herd the box, decalcification of the bones must be counteracted. Since the horse receives little to no concentrate during this time, only hay, it may be undersupplied with nutrients. Calcium is absorbed sufficiently by the horse through hay and does not need to be supplemented further or it will hinder the absorption of other important nutrients, such as zinc. The supply of organic magnesium is therefore of paramount importance in the case of strict stall rest.

Digestive and detoxifying herbs can continue to be used to counteract colic. Recommended are: Anise, fennel, artichoke, milk thistle, devil's claw, willow bark.

Preventing tendon damage in horses

• Warm up with 10-20 min. step
• Avoid cold starts (when left on paddock)
• No tight turns, especially without warming up
• Avoid uneven floors
• Do not jump too high too often
• Varied training to avoid one-sided stress; long walking tours, rarely lunging
• Regular, consistent exercise through daily exercise; create exercise incentives, e.g. through a paddock trail.
• Shoeing adjusted for malpositions
• Avoid heat-accumulating, tight-knit bandages/gaiters; however, compression bandages may help, according to studies
• Regular physical therapy to relieve muscle damage or tension that can lead to tendon overuse
• Nutrient supply of selenium, magnesium, collagen and manganese in organic form.

After the tendon damage: Training the horse

In the case of lighter tendon damage, controlled movement can be helpful during the regeneration phase in order to maintain the elasticity of the tendon. Otherwise, the tendon damage should first be completely healed and its full recovery confirmed with an ultrasound. If the horse is running without pain and lameness, it can be retrained.

It is started with a walking phase lasting weeks or months. To accustom the tendon carefully to the load, it is started with straight lines on hard ground. If the horse is to be ridden, it is imperative to make sure that it has no tension whatsoever. This is because tense muscles have a negative effect on the elasticity of the tendons, as these structures are closely interwoven.

The daily step duration is increased by minutes.

After a few weeks, curved lines and turns can be gradually incorporated. It is better to avoid very tight turns altogether.

Despite all caution, a proper, hindquarters activating training is necessary. The muscles must be built up correctly to prevent tension on the one hand, and on the other hand, this allows the horse to carry itself better. This takes load off the tendons.

Working on the lunge is completely unsuitable. The narrow circle requires too much one-sided loading, which the newly formed tendon fibers cannot bear.

As an incentive, we have created an exemplary training plan for the build-up after an injury-related break. put together.

FAQs - Frequently Asked Questions About Tendon Damage in Horses

1. How long does tendon damage in horses last?

Due to the poor blood supply to the tissue, tendon damage heals more slowly than injuries to other parts of the body. Therefore, healing processes are roughly pegged at up to one year. However, the actual amount of time depends on the horse, recovery management and the injury itself. A tendon fiber tear usually heals faster than a tendon rupture because less scar tissue needs to be formed.

Whether or when the horse is rideable again after a tendon injury cannot be answered in a blanket manner. In the case of chronic tendon damage that causes the horse repeated problems, the horse should possibly not be ridden at all. However, there are also individual cases that have jumped up to advanced level after a tendon injury has been cured.

2. Is the horse allowed to graze during this time?

In the first few days, box rest is best to get through the acute phase and avoid further injury. After that, the horse can be moved in a controlled manner, depending on the degree of injury. For exercise, this means that it must not buck around. Then a marked out area is recommended. It is important here to discuss the range of movement with the veterinarian.

3. Is the risk of further tendon damage after recovery higher?

A higher risk of further tendon damage after recovery is not necessarily present. Some horses have connective tissue weakness that can promote more frequent tendon injuries. Likewise, the quality and quantity of scar tissue plays a critical role in how sustainable the tendon is. If the newly formed tissue is not very elastic and the tendon is overloaded, the tension will be distributed unevenly - the healthy tissue will tear, just in a different place.

4. Does a horse with tendon damage have to be euthanized?

Tendon damage does not necessarily mean the end of a horse's life. After a sufficiently long and well-managed regeneration phase, the horse can still be used recreationally. Only when re-ruptures occur, i.e. recurrent tendon ruptures, the horse suffers from chronic pain and the quality of life is no longer sustainable due to permanent stall rest, can the final step be considered. However, as a rule, tendon damage in horses means the end of a sports career rather than the end of the horse in general.

5. Should I buy a horse with tendon damage without hesitation?

Anyone who has chosen a horse that is proven to have healed tendon damage prior to sale should be aware that the horse may have limited use. Before buying, the tendon should be sounded to make sure the damage is gone. This will give one an idea of the possibilities that still exist with the horse. One should still keep in mind that the horse may be more susceptible to secondary damage due to scar tissue. Daily, consistent exercise should be offered to the horse in its new environment and a critical eye should be kept on warm-up, variety in training and the supply of appropriate nutrients. 

6. What does tendon surgery on horses cost?

In a few cases, regeneration through box rest and local forms of therapy is not sufficient. Then the tendon of the horse must be operated. The cost of tendon surgery in horses cannot be generalized, as there are different methods for different tendon problems. However, one must expect at least 1,300€. Even with local treatment by injections, for example, you have to expect about 300 € upwards.

7. Are weak tendons in horses hereditary?

Horse breeding has changed a lot in the past decades: Whereas in the past horses were bred for work that were less rideable, today the focus is on rideable, soft horses. However, this softness also has consequences: In addition to genetic PSSM (muscle disease), it often leads to connective tissue weakness in horses, which can promote tendonitis and tears. Then it doesn't even take a big load to overload the horse's tendons and ligaments. So tendon problems are not inherited per se. However, it has been shown that horses that are bred to be especially rideable lose their robustness and are therefore more susceptible to tendon damage.