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Understanding Tendon Injuries

Posted in Horse Racing News

Your horse has injured one of the major tendons in his leg and your veterinarian says he’ll be laid up for nine to twelve months.

Bringing a horse back from a tendon injury is a long and also can be a frustrating process. There is no guarantee of success.  Injuries like these can end a horse’s career… but how you manage your horse’s injury can make all the difference in the outcome.

We will walk you through the steps to recovery and show you when and how you can help make a difference between success and failure.   We will also point out some of the problems and pitfalls you may encounter.

Injuries are common in the key tendons that run down the back of the lower leg.  The superficial and deep digital flexor tendons. The tendons extend from muscles high in the leg to the foot; when the muscles contract, they flex the horse’s leg. They also help to support the leg and they come under tremendous stress when a horse gallops, jumps or does any type of athletic maneuver.

Although we are discussing tendons, the steps we will cover also apply to injuries in the ligaments. Tendons and ligaments have different functions.  Tendons transfer the action of muscles to the skeleton, while ligaments connect bone to bone to keep joints from wobbling. Tendons and ligaments are formed of similar tissue and are injured by similar stress and they basically heal in the same way.

Tendons and ligaments go through the same phases of healing as skin or other body tissues, but the process is much, much slower because of the way they are built. Both structures are made up largely of an organized network of dense, elastic connective tissue, rich in a very tough protein called collagen. Living cells called fibroblasts maintain the network.

Fibers of collagen run lengthwise throughout the tendons. They stretch to take the load when your horse puts his weight on the leg and spring back like a group of rubber bands when the weight comes off.  If the horse overloads the leg (perhaps by just landing wrong on uneven ground), the fibers can tear. Tremendous damage can be instant or it can build up over time as repetitive loads outstrip the ability of the fibroblasts to keep up with repairs. There are relatively few of these cells compared to the amount of collagen in a tendon or ligament, and that’s one reason why these injuries heal very slowly. In addition to this, tendons and ligaments have poor blood supplies.

A severe tear will take longer to heal than a mild one, and a twelve-year-old horse may heal more slowly than a three-year-old. Typically ligaments heal a bit faster than tendons, but you still may be looking at nine to twelve months for all but the mildest of these injuries.  Sometimes these injuries heal poorly.  Instead of long, strong collagen fibers, you may get a disorganized tangle of scar tissue that’s much less elastic and more prone to reinjury.

To get the best outcome, you’ll need to follow a management and rehabilitation program that is carefully matched to the progress of healing.  Your veterinarian will help you set up a program that designed to fit your horse’s injury.  Diagnostic ultrasound scans, which many vets can do, will take much of the guesswork out of managing recovery and improve your odds of success.

Initially, ultrasound will show the extent of the injury.  The machine sends ultrasonic waves into the leg and captures their echoes as they bounce off tissues. A tear in a tendon may show up as a dark gap (or hole) in what should be a uniform pattern or as an area where echoes are less intense.  Repeat exams can show how healing is progressing, which will allow you to adjust your horse’s program. Your vet may want to do the exams at 30, 60 or 90 day intervals, depending on the severity of the injury, the stage of rehabilitation and the total rest time that is needed for healing.

The First Step: Cool Down The Injury
When a tendon tears, blood, and lymph fluid leak into the injured area.  Enzymes and other body chemicals rush to the site.  Inflammation builds, producing heat, swelling and pain.  While it’s part of the healing response, it can have harmful effects because it can worsen tissue damage in the injury.  Therefore, your first steps, while the injury is fresh, is aimed at cooling down the injured leg and reducing inflammation.

  • Cool Out: Cold-water hosing is the simplest way to draw heat out of the injury. Ice water is great… if your horse will stand in it, as are devices whirlpool boots that keep cold circulating around the leg.

Ice sessions should last 20 to 30 minutes and cold hosing it will take a little longer.  When you can feel that the injured area is cool, you’re ready for the next step. Repeat the treatment twice a day. You can cool more often if the injury is severe, but allow at least 30 minutes between sessions.

  • Wrap the injured leg: Dry the leg after cold therapy and apply a standing wrap (a leg quilt secured with a track bandage) to support the leg and help keep swelling down. You can use a mild poultice with the bandage to help draw out heat, but avoid any agent that could irritate the skin or increase inflammation. Bandage the opposing leg, as well, for support. Reset bandages at least once a day.
  • Medicate: Your veterinarian may prescribe medication, usually phenylbutazone (bute), flunixin meglumine (Banamine) or a similar nonsteroidal anti-inflammatory (NSAID) drug during this period. Besides reducing inflammation, these drugs help make your horse more comfortable.
  • Confine: In most cases, strict stall rest is best at first. Your horse will come out of his stall for cold-therapy sessions and, if your vet says its OK, you might take him out to hand-graze for short periods. If his injury is mild and he’s not lame, you may start hand-walking sessions. Otherwise, your horse should not be exercised or turned out. Adjust his feed accordingly. Plenty of grass hay will help keep him occupied, but he won’t need high-energy concentrates.  If he stall walks or gets anxious, an acrylic mirror may calm him down believing he has a partner next to him.

Cooldown takes anywhere from a couple of days for a mild injury to two weeks or more for a more severe tear. You will find that the leg is no longer hot or painful to finger pressure and your horse is sound at the walk. He’s moving into the next phase of healing.

Early Recovery
As the injury cools down, fibroblasts get busy producing new collagen to repair the damage. This healing should show up on ultrasound as thin fibrils of collagen begin to fill in the injury.

This is the point where many alternative treatments are applied.  These treatments tend to be most effective when given after cool-down but early in the healing process.

Whether you decide to use one of these treatments or not, good management is crucial in early recovery.

  • Heat – There are many different ways to go here.  You can use a light blister like DMSO with Ball Solution to a heavy blister, where your horse will need a cradle.  The choice is between you and your vet.  One recommended route is using green Palmolive dish soap as a blister.  It is an extremely humane blister and blows the legs up well.  As stated earlier, tendons have a weak blood supply.  By administering a blister, you are bringing more blood to the area, which will aid in healing.  With the Palmolive blister, you apply one day one, hand walk on day two and on days three, four and five, hose for 30 minutes, then hand walk for 30 minutes twice a day.  You can even begin swimming on day three.  On day six, you can begin washing with Castille soap, then wrap the leg in a Furacin sweat to remove the scurf.  If you the time and you feel it is needed, the entire process can be done again in seven to fourteen days, depending on the skin.  In the meantime, swim, hand walk or both.
  • Begin controlled exercise: Lightly movement on the injured tendon stimulates collagen formation plus it encourages the collagen fibers to align in a way that maximizes strength… BUT doing too much too soon risks re-injury.  With your veterinarian’s approval, begin short periods of controlled exercise.  Hand walking for perhaps 10 minutes twice a day at first. Do this on a level, smooth surface that’s not too deep. If all goes well for two weeks, you can begin to gradually increase the time.  You might add five minutes a day… in another week, five minutes more.
  • Medicate as needed: Reinjury is also a risk if your horse is playful when you walk him. If behavior’s a problem, talk to your vet about sedative medications to control him.  Generall,y horses should be off anti-inflammatory meds after cool-down. NSAIDs can have long-term side effects, and there’s some evidence that they slow healing.
  • Repeat the ultrasound: After a month to six weeks, your vet will probably want to repeat the ultrasound exam. The new scan should show more of the injury filling in with collagen plus the fibers, which were a disorganized tangled mess at first, should be starting to align in ways that will help the tendon withstand stress.

Getting Stronger
As healing progresses, collagen continues to be produced. It also remodels and it becomes denser and better organized in response to the mild stress of carefully controlled exercise. Remodeling makes the tendon stronger and able to carry greater loads, and increasing the loads in step with healing keeps the remodeling process going in the right direction.

  • Walk: With your vet’s approval, you may be able to replace one of your daily hand-walking sessions with walking under tack. Be sure your horse’s feet are properly trimmed and shod, and continue to work on a level, smooth footing, in straight lines and large circles.
  • Vet check: After about for to six weeks, have your vet check your horse’s progress.  If the ultrasound shows that healing continues to progress, it may be time to begin light work.
  • Trot: The first week, you might add just five minutes of trot to your exercise sessions. (Walk for a good 15 minutes first to be sure the tendon is warmed up.) After a week or two, if everything’s OK, add another five-minute interval, and then a third interval a week or two later. Keep the work easy.  Big circles are OK, but avoid sharp turns and lateral moves.  Don’t lunge  Repetitive circles can be hard on the healing tissues, and as a handler, you have little control over your horse’s behavior.
  • Repeat the ultrasound: If your horse continues to trot sound on circles and straight lines, and his leg shows no sign of heat or swelling, you may be able to gradually increase his work. Get new scans before any major increases in exercise.  The first canter, the first jump, the first gallop, the first jogging session.  Ultrasound should show fibers becoming denser and lining up parallel to each other, which will make the tendon stronger.
  • Turnout: When your horse is well along in his exercise program, your vet may tell you it’s OK to put him out in a small paddock. He should go out by himself, at a quiet time when other horses won’t be acting up. Any horse is likely to explode and run off when they first are turned out after months in a stall, so talk to your vet about a tranquilizer to keep him calm at least for a few days.  Don’t leave him out unwatched, and be ready to bring him in at the first sign that he’s acting up.

If your horse is sore after exercise or if you see a return of heat, swelling or pain at any point, back off the program and contact your veterinarian.  A return of soreness and heat isn’t always a big problem, but your vet may need to see your horse and perhaps do an ultrasound exam to find out what’s going on.

Here are two possibilities:

Adhesions: Adhesions are strands of fibrous scar tissue that form where they shouldn’t and restrict a tendon’s ability to stretch and glide. They develop mainly in injuries lower in the leg, the area just above, around and below the fetlock (ankle).  This is where the tendon passes over the joint.  It’s encased in a sheath that secretes lubricating synovial fluid.  Adhesions can form between the tendon and the sheath or between parts of the sheath.  An infection in the sheath can make this more likely.  Up higher in the leg, adhesions are rare… but in severe injuries (like a tendon laceration) they sometimes form between the superficial and deep flexor tendons.

Adhesions can make a horse very sore, but the fix is to go forward with your restricted exercise program. It is something that is expected and you are not re-injuring the primary issue.  It is something that will gradually stretch and remodel the adhesions, so they no longer trouble him.  Passive manipulation through the normal range of motion, ie: picking up the injured leg and gently flexing the foot, fetlock and knee (or hock if it is a hind leg tendon tear) can also help. You can do it while you’re grooming him or any time during the day.

Reinjury: Doing too much… too soon, is the most likely cause for a setback in healing.  When your horse is trotting sound after a few months into his rehab, it is easy to think that you’re past the danger point and it becomes very tempting to ask him for a little more. The fact is, his tendon is still healing. The site of his injury is still and it doesn’t take much to tear it again.

In this case, forging ahead with exercise will do more damage.  Depending on how much damage is done, reinjury can restart the clock on your rehab program, putting you back at the beginning. That’s why it is important to talk to your vet at any sign of soreness. Your vet can compare new and previous ultrasounds to see if there’s been a change in the tendon.

When can your horse return to competition? The answer depends on how severe his injury was to start with, how well it heals, and what your goal is with him.  After you’ve brought him through his nine to twelve-month recovery program, if he shows no lameness or heat, swelling or pain in the tendon, and his ultrasound looks good, he may be ready.  Unfortunately, reinjury is always a risk in tendons and ligaments because the new tissue that fills in the injury isn’t as strong or as elastic as the original.  It is basically scar tissue.  That weakness means that the old injury may give way under stress.

Researchers are always working on ways help tendons and ligaments heal “good as new.”  There are some injections available, including PRP (Plasma Rich Protein).  Speak to your vet about new options that become available, but the initial cooling out and rest will still be part of the program.

Many horses with these injuries do successfully return to their previous level of work and by giving continuing care to the injury, they may never have an issue again.

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