The Conservative Approach for Healing Horses
- Aug 1, 2012
Photo: Megan Arszman
Despite the numerous newfangled tricks and treatments available, time and R&R remain essential for helping a horse recover from tendon or ligament injury. That can be good or bad news, depending on owner expectations for the horse's performance.
Both tendons and ligaments are soft tissues. They sustain injury via similar forces, respond to damage in a similar fashion, and heal at almost the same rates. That typically amounts to eight months.
But why so long? The body's healing system is complex, explains Duncan F. Peters, DVM, MS, director of the Sport Horse Division at Hagyard Equine Medical Institute, in Lexington, Ky. While newer treatments might provide functional improvement in the healing process, they do not speed up the process itself, he notes. "The time factor is still necessary, and R&R is part of the process."
Tendon and ligament injuries arise from a variety of sources, such as conformational faults, fatigue, and lameness, that can lead to overload. Exercise-related tendon and ligament injuries might occur:
- When a rider works a horse lightly for most of the week, then works him strenuously on the weekend.
- When trainers work a group of horses on the same training schedule even though the animals vary in their responses and need individual programs based on physical condition, maturity, and temperament.
- When a horse guards a painful area, resulting in overuse of other parts of an affected limb or other limbs.
- When an awkward step or odd positional stress overloads tissue, undermining its strength and damaging fibers.
Because such injuries are an inherent risk of high-level performance, says ultrasound consultant Johanna Reimer, VMD, Dipl. ACVIM, of Georgetown, Ky.
Unfortunately, there are no accurate methods to assess musculoskeletal fatigue while it's occurring, says Carol Gillis, DVM, PhD, Dipl. ACVSMR, of Equine Ultrasound and Sports Medicine, in Aiken, S.C. As muscles tire, tendons, ligaments, and joints experience imprecise loading. As tendons and ligaments approach their breaking strength during activities, the imprecise loading can lead to fiber tearing.
For the rider or owner, decreased performance might be the first sign something is going wrong. The horse might exhibit an attitude change or a gait change while performing certain exercises, says Peters.
"Horses with tendon and ligament injuries spend little time being lame at a trot on the straight or the longe line and much time underperforming or reluctant to work," says Gillis, because tendon and ligament tissues contain relatively few pain receptors. The owner might initially interpret the action as a training or behavior issue and deal with it accordingly.
Generally, the injury becomes apparent only after tissue sustains significant damage--evidenced by heat, swelling and pain upon palpation--and is accompanied by an altered gait.
The veterinarian's expertise, experience with these injuries, and access to diagnostic tools can make a difference in the prognosis. Peters says it is important to understand that "tissue damage can look quite different 10-14 days later in the (healing) process, so it may be important to hold off with a prognosis till a bit down the road."
Injuries by Activity
Our sources agree that the tendons and ligaments horses most commonly injure are the superficial digital flexor tendon (the classic "bowed tendon") and the suspensory ligament apparatus. "These two structures are involved in support and flexion of the fetlock, which is the major load-bearing joint in the horse," says ¬Gillis.
Reimer says she most often finds bowed tendons and torn suspensories in racehorses; suspensory injuries in show hunters and jumpers; forelimb bowed tendons and fore and hind limb suspensory injuries in upper-level event horses; front suspensory injuries in reiners; front and hind suspensory injuries in upper-level dressage horses; and inferior check ligament (which connects the deep flexor tendon with the cannon bone just below the knee) injuries in horses at pasture or that have taken a "bad step."
But the damage might extend beyond these structures. Gillis says veterinarians are realizing more and more that "arthritic" conditions in the foot and in joints often begin as soft tissue injuries of the collateral ligaments or other structures involved in joint ¬stabilization. "We have traditionally believed that a joint showing inflammation which has clean or normal radiographs (X rays) does not have a serious problem," says Gillis. "However, damaged soft tissues in and around the joint will result in continued instability, inflammation, and eventually arthritic changes visible on radiographs if the joint is simply treated with injections to alleviate pain and inflammation temporarily without addressing the underlying cause."
Injury prompts a cascade of distinct processes. The first is inflammation, the body's protective response, lasting three to four weeks. Increased blood flow associated with inflammation prompts the body's first-aid team--cellular and biochemical processes that stimulate tissue regeneration.
The next stage, beginning about a week after the injury, overlapping the inflammatory stage and lasting about three weeks, is marked by angiogenesis. In this process the body builds new capillaries to enable water and chemical exchange between blood and surrounding tissues. Tendons and ligaments typically have a relatively poor blood supply. However, Gillis says, with injury the number and size of vessels triples in tendons and ligaments. Scaffolding also forms for fibroblasts (cells that form connective tissues) to accumulate and build new tissue.
In the third stage, stretching from about Weeks 4 to 16, type III collagen--a type of structural protein--fibrils form as part of the healing response. Many fibrils then aggregate and link together to form collagen fibers, then fascicles. Several fascicles ultimately form new tendon or ligament.
In the final phase, 16 to 32 weeks into the healing process, type I collagen, the protein found in normal tendon and ligament tissue, replaces the weaker type III collagen and increases structural strength.
Coordinating with Nature
To synchronize with the body's own natural healing response, our sources advise first confining the injured horse to his stall and then gradually increasing duration and intensity of exercise. They agree that any overexercise would lead to a cycle of partial healing and reinjury. However, veterinarians' specific recommendations for return to exercise differ.
In general, cold therapy or cold hydrotherapy and systemic medications help control initial cellular mediators of inflammation that can damage tissue. Bandages hold topical anti-inflammatory medications on the area and reduce edema (fluid swelling) and other swelling, says Reimer.
For the first five weeks or so post-injury, Gillis advises hand walking the horse, walking him on a water treadmill, or walking him on a free exerciser. While owners should generally wait to ride, Reimer says she does allow walking under saddle with a light rider with or without a pony (for control and companionship), if necessary, because some horses might be difficult to control in hand.
From Weeks 4 to 16, Gillis suggests the owner or caretaker walk the horse under tack, increase his time walking on a free exerciser, or pony him from another horse at a walk.
In her experience, Reimer says many caretakers rehabilitate Thoroughbred racehorses with bowed tendons successfully with one month of stall rest and hand walking followed by three months of turnout in a small paddock. However, Gillis says she has performed ultrasound on horses after this small paddock rest regimen and found that tendons/ligaments are not healed completely to full strength.
During the first part of the last phase, Weeks 16 to 24, Gillis recommends the owner walk or trot the horse under tack (mounted or unmounted) or in a free exerciser. Reimer allows cantering as well as small paddock turnout at this time, provided the horse is sound and ultrasound findings show improvement.
From Weeks 24 to 32, Gillis advises increasing canter work. After one week of canter under saddle the owner can turn the horse out to canter freely for the first time in rehabilitation, as he should now be conditioned to that level, says Gillis.
Sport-specific training now predominates: speed work for racehorses, cavaletti for jumpers, increased lateral work and collection for dressage horses.
Other useful therapies our experts consider during rehabilitation include ice water, whirlpool boots, therapeutic laser, therapeutic ultrasound, electromagnetic therapy, heat, massage, chiropractic adjustment, acupuncture for pain, and muscle relaxants for spasms associated with back or neck injuries.
Chances of Recurrence
For horses sent back to work before injuries heal completely or with underlying issues that have not been identified and treated appropriately, the recurrence rate is high. Injury recurrence can also happen because the tissue is not as resilient and elastic as the original and might not respond to loads as well as the parent tissue, says Peters.
"The published success rate (i.e., the horse goes back to the same level of work or better without reinjury) for any soft tissue injury, no matter what the medical or surgical treatment, is 50 to 60%," says Gillis. "For a whole horse approach that identifies and treats all problems simultaneously and uses diagnostic ultrasound effectively to guide the rehabilitation process, my success rate since 1999 is 80 to 90%."
In a survey she conducted of 145 horses discharged from the Equine Ultrasound Unit at the University of California, Davis, Gillis determined horses that completed a rehabilitation program successfully and were judged to be 95% healed on the last ultrasound were able to return to work at their previous level of performance with no greater risk of reinjury than a previously uninjured horse.
"This is the reason to follow a controlled exercise program based on regular clinical and ultrasonographic exams until the injured tendon or ligament is completely healed based on strict imaging criteria," she says. "Unfortunately, however, some injuries are career-ending or are of a degree that the horse will be unable to return to the previous level of performance regardless of the time and treatments given."
An experienced veterinarian can design an individualized rehabilitation program suitable for your horse's injury, his temperament, and your resources.
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