By, Annette McCoy, DVM,
Courtesy of University of Minnesota
“Bowed tendon” is the common name for superficial or deep digital flexor tendonitis. The superficial digital flexor tendon (SDFT) runs down the back of the leg and attaches to the long and short pastern bones. The deep digital flexor tendon (DDFT) runs to the SDFT and attaches to the coffin bone. Together, these tendons aid in flexion of the lower limb.
When either of these tendons becomes inflamed, it swells, causing it to look “bowed.” The bow can appear anywhere from the carpus/tarsus (knee/hock) to the pastern region. The SDFT is much more commonly affected than the DDFT.
Bowed tendons can occur as a result of chronic stresses on the flexor tendons or as a result of a single traumatic incident. Racehorses, polo ponies, and jumpers are at higher risk than other equine athletes for developing this condition. Placing bandages on the lower leg that put uneven pressure on the tendons can also lead to inflammation.
Bowed tendons can vary in severity, but because of the type of tissue involved in the injury, complete healing takes a long time. Clinical signs may resolve within days if the horse is rested and given anti-inflammatory drugs (i.e. Bute), but generally return when the horse is returned to work. It can take 8 to 11 months for the tendon to repair itself completely.
Treatment primarily consists of complete rest followed by a controlled, gradual return to exercise, anti-inflammatory drugs, and occasionally, surgery. Prognosis for return to athletic work depends on the severity of the original injury, and the condition can recur, particularly if stresses are added to the leg prematurely. Repeat ultrasound examinations are used to monitor healing and allow return to exercise as fast as possible without re-injury.
There are many new treatment options for bowed tendons on the market, including injecting the tendon with cells taken from fat or specially treated blood, and shockwave therapy. These, and a variety of other treatments, have become popular over the past decade but unfortunately, most are eventually shown to be useless or even damaging.
For example, a product taken from bladder mucosa was popular last year; it is now avoided. Fat cell injections are currently popular, but scientific research has been done on only four horses. Shockwave therapy has been shown to assist with arthritis pain and newer treatments are still being tested. Currently, research is being conducted on stem cells, special antibodies, and platelet rich plasma along with specialized rehabilitation programs.
If you decide to pursue a treatment, take time to become informed on the pros and cons and count on a prolonged rehabilitation period.