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Equine Health Resource

Flexor Tendon Injury, Tendinitis, Bowed Tendon

Synonyms: Superficial Digital Flexor Tendinitis, Deep Digital Flexor Tendinitis, Bandage Bow, Compression Bow

A tendon is the attachment of a muscle to bone. The equine flexor tendons are highly specialized and vitally important structures in the lower limb. The muscles that attach to these tendons are in the upper limb, but the tendons run down the rear of the lower limb, below the carpus of the front limb or the hock of the hind limb. Here they attach to the pastern bones or P3 (depending upon the tendon), below the level of the fetlock. The flexor tendons support the full weight of the horse in weight bearing and normally tolerate tremendous tension.

Tendons have very little blood supply and therefore heal very slowly. When examined under the microscope, ligaments and tendons are composed of highly organized dense connective tissue that is extremely strong. Generally, they heal through the formation of scar tissue, which is never as strong or as flexible as the original structure. Due to this, re-injury is common.

A strained tendon is one in which tendon fibers have been torn or damaged.

When strained, these tendons become enlarged and bulge out, and this appears as a long vertical swelling that gives the affected leg a distinctly “bowed” contour. New injuries are soft, warm and painful to the touch. Over time the injuries become firmer and cool, as they are mostly scar tissue. Initially, horses with strained flexor tendons are moderately to severely lame, depending upon the tendon involved and the severity and location of the tear.

Flexor tendon injuries are common in performance horses of various disciplines and breeds. Bowed tendons are also more commonly seen in horses with long weak pasterns, and as a result of improper shoeing. These can be severe injuries that take a long time to heal due to the mechanics of the flexor tendons. In addition, re-injury is common in performance horses.

Diagnosis requires a clinical lameness exam, and careful assessment of the affected area. Ultrasound is by far the most useful diagnostic for assessing these soft tissue injuries.

There are now many more treatments available, including the regenerative therapies, which are being claimed to be far more effective than prior treatments. Regardless of the injury, a critical part of effective treatment is a graded return to fitness and gradual strengthening and repair and remodeling of the injured tendon.

Prognosis & Relevant Factors

The prognosis is guarded to poor for return to pre-injury performance levels. The specific prognosis depends on the specific nature of the injury, i.e. what structures are involved and where. The cross sectional area of the tendon that is damaged is, as expected, also a factor in prognosis. Improved healing may result from some of the new therapies available.

The scar that develops in a tendon or ligament is never as strong as the original tendon tissue. So re-injury is always a concern. In some cases, horses may need to rest and rehabilitate for a year or longer after a tendon injury.

QUESTIONS TO ASK MY VET

  • What is the latest research suggesting that one or the other of the "regenerative therapies" is superior?
  • Can you direct me toward research supporting that?
  • PREVENTION

    Select horses of good conformation for your intended purpose or discipline.

    Conditioning: Tendons strengthen with conditioning and gradually increasing load. Always over-condition your horse for the work asked of him. Long, slow, distance work-such as a 30- to 45-minute walk/ trot -is ideal, as this strengthens tendons and ligaments without stressing them. Ensure overall fitness exceeds work level and expectations.

    Good footing. Uneven or deep footing causes tendon and ligament injury. Never ride a horse in bad footing (too deep or too thin or hard).

    Hoof care: Appropriate shoeing or trimming, and prevention of hoof overgrowth is critical for minimizing stress to tendons and ligaments. Keep your horse on a regular (6-8 week) shoeing or trimming interval.

    Warm-up: Plan to walk a horse under saddle a minimum of 10 to 15 minutes before you start to work.

    Recognize subtle signs of lameness before they become severe. Notice swelling, heat or digital pulse in your horse's limbs by learning what constitutes normal (WHE). Observe your horse's limbs before you ride and take note of any changes you notice.

    Helpful Terms & Topics in HSVGWritten, Reviewed or Shared by Experts in Equine Health

    Author: Doug Thal DVM Dipl. ABVP

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