Bowed tendon

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Tendinitis /tendonitis is inflammation of a tendon, often involving torn collagen fibers. A bowed tendon is a horseman's term for a tendon after a horse has sustained an injury that causes swelling in one or more tendons creating a "bowed" appearance.

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Bilateral bowed tendons. Bowed Tendons.jpg
Bilateral bowed tendons.

Description of tendinitis in horses

Tendinitis usually involves disruption of the tendon fibers. It is most commonly seen in the superficial digital flexor tendon (SDFT) in a front leg—the tendon that runs down the back of the leg, closest to the surface. Tendinitis creating a "bow" is uncommon in the deep digital flexor tendon (DDFT) of a front leg, but is not uncommon in the pastern and foot regions. Tendinitis of the SDFT or DDFT in the hind leg is less common.

When the SDFT is damaged, there is a thickening of the tendon, giving it a bowed appearance when the leg is viewed from the side. Bows usually occur in the middle of the tendon region, although they may also be seen in the upper third, right below the knee or hock (high bows), and lower third, just above the fetlock (low bows).

Causes and factors of tendinitis in horses

Excessive Strain

Excessive strain on a tendon can damage its collagen fibers. This is most commonly seen in performance horses that gallop or jump, who usually strain a tendon as a result of fetlock overextension when their weight is loaded on one leg. The overextension of the fetlock causes overstretching of the flexor tendons, resulting in the rupture of tendon fibers. Horses in intense training, especially those that were not conditioned properly, may damage many collagen fibers. This may occur gradually or suddenly.

After the fibers are torn, the tendon hemorrhages and collects fluid (edema), creating swelling and lameness in the area as well as increasing the pressure. The increase in pressure may damage the tendon further by destroying the cross-linking of undamaged collagen fibers and preventing the flow of blood to the area.

The SDFT

The middle third of the SDFT is most likely to suffer from tendinitis for several reasons.

The SDFT is narrower in its middle third than its top or bottom sections, making it weaker. The top and bottom of the SDFT has a better supply of blood as well, with the top third supplied by the vessels from the knee, and the bottom third supplied by the vessels in the fetlock. The middle third has a poor supply of blood, relying on the tiny vessels of the peritendon (the membrane that surrounds the tendons). If this supply is for some reason compromised, the collagen fibers in the area may die, weakening the tendon in that area and making it more likely to tear.

The SDFT branches below the fetlock, creating a sling under the back of the joint. Thus, overextension of the fetlock is more likely to overstretch the SDFT than the DDFT, which simply travels straight down behind the fetlock and pastern, to attach to the coffin bone.

Other Factors

Each of these factors encourage the overextension of the fetlock and knee during work. Several of these factors at once can add up.

Bandage bows

Bandage bows are caused by applying a bandage too tightly, creating an acute pressure injury to the tendons. The compression may cause the area to swell once the bandage is removed, giving a "bowed" appearance. However, the damage is often just to the skin and not to the tendon itself, but tendon injury can occur from impaired blood flow.

Horses with bandage bows usually respond to sweats or poultices. These treatments must be applied under a bandage that is not tightly fitted and the bandage should only be left on for a few hours. Cold hosing, NSAIDs and DMSO may also help.

Signs of tendinitis in horses

Signs of acute tendinitis include swelling, heat, and pain when the affected area is palpated. If mild, swelling may not be readily apparent, although there will still be heat and pain in the area, as well as mild lameness. If more severe, the injury is usually accompanied by moderate lameness (2-3 on a scale of 5) with obvious swelling.

It is important not only to palpate the SDFT but the branches of the SDFT, the DDFT, check ligament, and suspensory ligament as well. These structures could have been damaged at the same time as the SDFT. Both legs should be checked, although tendinitis usually only occurs in one leg.

When the tendon is healed, it will still have a thickened, bowed appearance that feels firm and woody. However, all heat, lameness, and pain should disappear.

Treatment of tendinitis in horses

Initial treatment of a bowed tendon should concentrate on anti-inflammatory therapies, including cold water or ice therapy, and anti-inflammatory medications on the direction of a veterinarian. The horse should be confined to a small area until the severity of the injury can be assessed with ultrasound. Standing bandages are helpful, but care should be taken to avoid applying them too tightly. [1]

Controlled exercise

Generally speaking, the most important aspect of long-term therapy is controlling the level of exercise. [2] A balance must be struck between two competing ideas:

For the first several months, large area turnout is discouraged, since even a small amount of running or playing could easily re-injure the weakened tendon. As the tendon heals, it is loaded in increasing amounts. The use of diagnostic ultrasonography is extremely valuable in guiding changes in workload. [1]

Adjunctive therapies

Many adjunctive therapies have been attempted to improve the quality of healing or to speed the recovery process. There is no consensus in the veterinary community as to which treatments are the most effective.

Prognosis of tendinitis in horses

The prognosis for return to full work depends on:

The best way to ensure that an injured horse returns to full work is to rehabilitate the animal correctly. This includes slowly bringing the horse back into training, and giving the horse light exercise each day as the tendon is healing. An impatient trainer who rushes to bring the horse back to intense training is likely to cause re-injury of the tendon.

Prevention of bowing and reducing the risk of re-injury to tendons

Sources

King, Christine, BVSc, MACVSc, and Mansmann, Richard, VDM, PhD. "Equine Lameness." Equine Research, Inc. 1997. Pages 400-415, 532-533.

See also

Related Research Articles

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A tendon or sinew is a tough, high-tensile-strength band of dense fibrous connective tissue that connects muscle to bone. It is able to efficiently transmit the mechanical forces of muscle contraction to the skeletal system without sacrificing its ability to withstand significant amounts of tension.

Tendinopathy Medical condition

Tendinopathy, also known as tendinitis or tendonitis, is a type of tendon disorder that results in pain, swelling, and impaired function. The pain is typically worse with movement. It most commonly occurs around the shoulder, elbow, wrist, hip, knee, or ankle.

Sprain Damage to one or more ligaments in a joint

A sprain, also known as a torn ligament, is the stretching or tearing of ligaments within a joint, often caused by an injury abruptly forcing the joint beyond its functional range of motion. Ligaments are tough, inelastic fibers made of collagen that connect two or more bones to form a joint and are important for joint stability and proprioception, which is the body's sense of limb position and movement. Sprains can occur at any joint but most commonly occur in the ankle, knee, or wrist. An equivalent injury to a muscle or tendon is known as a strain.

Achilles tendinitis Medical condition

Achilles tendinitis, also known as achilles tendinopathy, occurs when the Achilles tendon, found at the back of the ankle, becomes sore. Achilles tendinopathy is accompanied by alterations in the tendon’s structure and mechanical properties. The most common symptoms are pain and swelling around the affected tendon. The pain is typically worse at the start of exercise and decreases thereafter. Stiffness of the ankle may also be present. Onset is generally gradual.

A soft tissue injury is the damage of muscles, ligaments and tendons throughout the body. Common soft tissue injuries usually occur from a sprain, strain, a one-off blow resulting in a contusion or overuse of a particular part of the body. Soft tissue injuries can result in pain, swelling, bruising and loss of function.

Navicular syndrome, often called navicular disease, is a syndrome of lameness problems in horses. It most commonly describes an inflammation or degeneration of the navicular bone and its surrounding tissues, usually on the front feet. It can lead to significant and even disabling lameness.

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Stable bandage

A stable bandage, or standing bandage/wrap, is a type of wrap used on the lower legs of a horse. A stable bandage runs from just below the knee or hock, to the bottom of the fetlock joint, and protects the cannon bone, tendons of the lower leg, and fetlock joint.

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Equine anatomy refers to the gross and microscopic anatomy of horses, ponies and other equids, including donkeys, mules and zebras. While all anatomical features of equids are described in the same terms as for other animals by the International Committee on Veterinary Gross Anatomical Nomenclature in the book Nomina Anatomica Veterinaria, there are many horse-specific colloquial terms used by equestrians.

Pastern

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Osselet is arthritis in the fetlock joint of a horse, caused by trauma. Osselets usually occur in the front legs of the horse, because there is more strain and concussion on the fetlock there than in the hind legs. The arthritis will occur at the joint between the cannon bone and large pastern bone, at the front of the fetlock.

Skeletal system of the horse

The skeletal system of the horse has three major functions in the body. It protects vital organs, provides framework, and supports soft parts of the body. Horses typically have 205 bones. The pelvic limb typically contains 19 bones, while the thoracic limb contains 20 bones.

Lameness is an abnormal gait or stance of an animal that is the result of dysfunction of the locomotor system. In the horse, it is most commonly caused by pain, but can be due to neurologic or mechanical dysfunction. Lameness is a common veterinary problem in racehorses, sport horses, and pleasure horses. It is one of the most costly health problems for the equine industry, both monetarily for the cost of diagnosis and treatment, and for the cost of time off resulting in loss-of-use.

Curb is defined in older literature as enlargement secondary to inflammation and thickening of the long plantar ligament in horses. However, with the widespread use of diagnostic ultrasonography in equine medicine, curb has been redefined as a collection of soft tissue injuries of the distal plantar hock region. Curb is a useful descriptive term when describing swelling in this area.

Racehorse injuries and fatalities are a side effect of training and competition. The problem with equine injuries is that they so often result in death. A 2005 study by the United States Department of Agriculture found that injuries are the second leading cause of death in horses, second only to old age. Nureyev's recovery from a broken leg while retired at stud in 1987 typifies the struggle horses have after being injured.

Limbs of the horse Structures made of bones, joints, muscles, tendons, and ligaments

The limbs of the horse are structures made of dozens of bones, joints, muscles, tendons, and ligaments that support the weight of the equine body. They include two apparatuses: the suspensory apparatus, which carries much of the weight, prevents overextension of the joint and absorbs shock, and the stay apparatus, which locks major joints in the limbs, allowing horses to remain standing while relaxed or asleep. The limbs play a major part in the movement of the horse, with the legs performing the functions of absorbing impact, bearing weight, and providing thrust. In general, the majority of the weight is borne by the front legs, while the rear legs provide propulsion. The hooves are also important structures, providing support, traction and shock absorption, and containing structures that provide blood flow through the lower leg. As the horse developed as a cursorial animal, with a primary defense mechanism of running over hard ground, its legs evolved to the long, sturdy, light-weight, one-toed form seen today.

Milomir Kovac Servian-German veterinary surgeon (born 1962)

Milomir Kovac is a Serbian-German veterinary surgeon, equine specialist, columnist, and author of university textbooks.

The treatment of equine lameness is a complex subject. Lameness in horses has a variety of causes, and treatment must be tailored to the type and degree of injury, as well as the financial capabilities of the owner. Treatment may be applied locally, systemically, or intralesionally, and the strategy for treatment may change as healing progresses. The end goal is to reduce the pain and inflammation associated with injury, to encourage the injured tissue to heal with normal structure and function, and to ultimately return the horse to the highest level of performance possible following recovery.

References

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