Tendon injuries are all too common in the horse and are not just confined to the equine athlete. Any horse can succumb to a strained tendon, even on pasture, with a wrong step or muddy footing. Despite the injuries being common, the recovery process can be quite extensive for many, resulting on a significant time lost, and money spent. In many of those cases, despite following recommended therapies, the outcome is less than expected and many horses fail to return to full soundness. Why are tendon and ligament injuries so difficult to recover from? Is there something you are missing to aid with a better recovery for your horse?
A tendon or ligament injury is one of the most concerning of injuries for most horse owners, mainly because of the expected long recovery time and often, a poor prognosis for return to full soundness. While many do quite well, others do not fare out well and cannot return to their prior level of work. In most cases, the owners are left with constant stall confinement often for 6 or more months, which can be aggravating and create its own set of problems.
In most cases of tendon injuries, horse owners are dealing with damage to the superficial or deep flexor tendon, but many also contend with injuries of the suspensory ligament or apparatus. The degree of lameness is often reflective of the severity of the injury, with some being more mild in lameness than others. Some horses can be just slightly ‘off’ in their stride or movement, while in other cases the horse can demonstrate an obvious head bob even at a walk.
What causes a tendon to become injured in the horse?
A tendon is an elastic type of tissue that connects muscle to a bone. As the muscle contracts, the bone is then pulled in the direction intended, often to flex or extend a limb or joint. Tendons are present almost everywhere we see a muscle belly. Common examples in the horse are the superficial and deep flexor tendon, located on the back of the cannon bone region, and the common digital extensor tendon located on the front.
In comparison, a ligament is a semi-elastic structure that connects bone to bone, often bridging one or more joints to provide external stabilization to that region. Common examples include the suspensory ligament, but also lateral and medial collateral ligaments that aid to stabilize joints such as the fetlock, carpus, and stifle joints.
For a tendon or ligament to become injured, it first implies that they exceeded their elastic or tensile strength. This means that essentially, they were over exerted, which may be common with various events such as jumping or even during accidental slips as seen in mud. The longitudinal fibers present within the structure are stretched beyond their normal limit, resulting in micro-tears and injury.
The other thing to consider is that various factors play into that increased exertion, including poor foot balance from trimming or shoeing, conformation, and diet. A foot or hoof that is out of balance will create more stress upon a ligament or tendon, which would include an under-run heel as an example. Conformation plays a role as well, increasing stress upon structures including tendons and ligaments. A horse that is toed in, as an example, may then put more strain upon lateral ligaments of the fetlock and the lateral branch of the suspensory ligament.
Diet also plays a vital role in tendon health and predisposition to injury. The tendon is composed of living cells that require nutrients, including protein, macro- and micro-nutrients. Not much different than other cells in the body. When they are not being fed properly, their overall health will decline, and the structure can become weaker overall. This is not uncommon to see in many horses and most often noted with other problems such as poor hoof condition, poor hair coat, stamina, recovery, or otherwise.
In my experience, a single incident of a tendon injury is not uncommon due to improper footing or landing during an event. However, these injuries often heal and recover quickly and uneventfully. When we have recurrent tendon injuries in a horse, or failure to mend in a reasonable period, then often there are other connectors in the problem.
Diagnosing the Damaged Tendon or Ligament in the Horse
In most cases of a tendon or ligament injury in the horse, the lameness associated can be generally mild and often only noticeable during a higher gait or work. In other cases, the lameness is more severe, resulting in a visible lameness at a walk with an obvious head bob when putting weight on the affected limb. Most tendon and ligament injuries are commonly found in the forelimbs, while a smaller percentage are present in the rear.
Making the diagnosis can be as complex or simplistic as you wish to make it. In most cases, a tendon or ligament injury can be highly suspected based on the nature of the trauma and palpation of the affected structure, noting heat and sensitivity to palpation or deep pressure. In almost all these cases, the horse is capable of bearing weight on the affected limb and will often yield the opposite limb when asked which can help us to rule out a major bone fracture or sometimes a joint injury.
In most cases, a joint or bone injury can be ruled out just by an examination, while in others it may be more confusing and thus, radiographs may be taken of the area to make sure there is no damage. After ruling out a bone or joint and having a suspicion of a soft tissue structure injury, an ultrasound is often the next step. The ultrasound examination allows the veterinarian to visualize the soft tissue regions that do not show up readily on radiographs. Your veterinarian can see the ligaments or tendons, assess for damage including core defects, but also evaluate for fluid accumulation around the structure.
An ultrasound examination is routine in most cases of tendon or ligament injuries, helps to confirm the diagnosis, and evaluate for severity of the injury. In more involved cases, other diagnostics may be performed including an M.R.I. evaluation, which allows for deeper analysis of the tissue.
Healing and Recovering the Damaged Tendon or Ligament in the Horse
Now that a diagnosis has been made, what is the best way to heal that structure for the optimal outcome? The answer to that question is highly debatable and I’m not sure any one person has the answer. Some of the most highly experienced veterinarians may have one strategy that appears to work, while a seasoned horse owner may have an entirely different approach. Both may seem to work but have different approaches to the problem. Which one is right?
How long does it normally take a tendon or ligament to heal? That is a good question and there is likely no straight forward answer. Looking at the normal healing process of a laceration, the general length of time of 7-14 days is expected. Now, of course, a tendon or ligament is a different structure than skin, being under more daily exertion, so that 7-14-day window of recovery time may not be enough. In most acute cases that I have contended with in my practice, they are well on the road to recovery in 2 weeks with most showing dramatic improvement in the first week. I have consulted on cases that have been stall rested with no improvement for periods of time from 6 months to 2 years. This extended period of time for recovery should raise a question.
The general theory that is applied to most is stall rest often along with other medications to help ease pain and discomfort. Some may use topical sweats or even poultices to aid the healing. Overall, it is really a question of how acute that condition is in your horse.
In the acute stage, implying that the injury just happened over the past day or two, there is often moderate heat, pain, and swelling to the region. In those cases, the goal is to allow for rest and to counteract the inflammatory process to help control healing. The inflammatory process is required for healing, but when this process gets too active, more damage can be created in the form of scar tissue which can then impede tendon/ligament function in the long term.
In the acute phase, therapies intended to pull or reduce the heat are needed. These include application of cold-water therapy and poultices. Stall confinement is often recommended to reduce movement and pain medications are also administered.
In the chronic phase, the circumstances are different. A chronic tendon or ligament injury is, by definition, one that has been present for 30 days or more. In the chronic phase, most are not dealing with a tremendous amount of external heat and the lesion is often perceived as being cold. Here, you do not want to cool down the injury with cold water hosing or poultices, but more often, your goal is to warm it up a notch and improve circulation to the region. Instead of cold-water therapy, we may choose warm water soaks and instead of poultices, you may elect for a topical sweat consisting of Dimethylsulfoxide (DMSO) with or without a corticosteroid.
The response to traditional treatment methods outlined above can be highly variable. As mentioned, some horses respond very quickly while others do not. In more advanced or chronic, stubborn cases, more involved therapies may be utilized including tendon-splitting procedures, stem cell injections, platelet rich plasma or other ‘regenerative’ types of options. The longer a case persists, and the more involved options need to be explored, often the worse the outcome for the patient. The reason for this is the fact of chronicity, and that as more time goes by, with inflammation being inflammation, the more scar tissue and cellular changes are created. The more scar tissue and damaging effects of inflammation, the less likely to regain full soundness.
Applied Insights into Tendon and Ligament Healing in the Horse
As a practicing veterinarian, I have applied most traditional therapies to my equine patient affected by a tendon injury. In the early years, I too, struggled with many patients and could not appreciate the true recovery. I was applying all that I was taught and knew at the time, but many just did not do well. When I took a different look at the problem, I began to apply new therapy options, and soon the recoveries were not as difficult.
From my point of view, that damaged structure, whether if it is a tendon or ligament, wants to heal. In reality, it is no different than a laceration to the skin or some other wound. That tendon or ligament injury is a wound, but we can’t appreciate it so much because it is out of sight, covered by skin. If we looked more closely, we’d likely see that there are similarities in healing methodologies to a skin laceration. We know it can heal. It wants to heal, but we just need to address it properly.
In our rehabilitation practice, working with OTTB’s, one of the most common injuries we contend with are tendon problems. Some are acute in nature, but most are chronic and have undergone months of stall rest, pasture turnout, topical therapies, injections, and even some have experienced advanced regenerative techniques. All the horses in our program were deemed unsalvageable by most standards, with owners and trainers giving up after all other efforts were exhausted and finances drained. Despite the poor prognosis and history, over 90% of these horses return to almost full work in a short period of time. That time length can be 2 weeks, or it can be 2 months, but most do not require longer. They are not just back to walking without a lameness, but most are back in work and under saddle. How can this be, when their prior owners have struggled with them?
The first thing I do is look at the horse, seeing past the tendon injury. What else is going on in that animal? How is diet? Stress? Have they been on turnout or stalled? How are the feet and conformation? All too often I think we just focus on the tendon and forget about the whole patient. Once you realize that all things are interconnected, the healing comes at a much more rapid pace.
Diet and Recovering from Tendon and Ligament Injuries in the Horse
Diet is paramount as all cells require nutrition for function and the healing process. Tendons have a limited blood circulation and mainly acquire their nutrient provision via diffusion from the space around them, but in the end, nutrition is nutrition. In our program, we focus on high quality nutrition, relying on nutritious forage as our baseline in the program. This includes nutrient rich hay such as alfalfa or a mix, but also adequate pasture with plenty of greens for consumption. This is the base for our nutrition program, and then we assess whether if that patient requires more. This is not determined by blood tests of specific nutrients, but more so by observing them, how they are healing, how they are responding. Look at the hair coat, the hoof condition, the brightness of their eyes, and their body condition.
Many owners and veterinarians will simply supplement a horse with a synthetic based vitamin/mineral supplement, hoping to fill in gaps in the nutrition program. This works for some owners, but it is not a general concept that we adopt in our program. Using isolated nutrients is not natural and often creates absorption concerns. Secondly, by using isolated nutrients, you may be missing out on vital co-factors present in the food sources that can benefit health and healing. In our patients, we focus on whole food nutrition, using forage and pasture as the main source. If we feel the patient needs additional resources, then whole-foods are implemented. These whole foods come from many sources, including spirulina blue-green algae, alfalfa powder, red clover, beets, potatoes, carrots, peas, flax seed, whole grains, pea protein extracts, spinach, barley grass powder, and many other sources. When they are fed, they are fed in adequate volumes, using a certified powder form. They are fed in combinations, to achieve synergism, often in amounts of 30-100 grams per feeding.
In other cases, if the core nutrition program is adequate, we may just focus on protein and amino acid provision to impact the tendon or ligament healing process. All nutrients are required for tissue function and repair, but protein is often overlooked. Many horses are fed low quality hay sources and are limited to stall confinement, thus reducing pasture access. Given this, not only do we need a boost in nutrient levels, through whole foods, but protein may need to be increased additionally. One means of supplementing additional protein is via plant based concentrated extracts, which include hemp or pea protein. Both are vegan or plant based, but hemp generally provides 50% protein while pea protein provides 80%. Pea protein generally has a more balanced amino acid provision, a more complete protein source, as compared to hemp protein. Lysine is one amino acid that hemp protein generally is lower in, as compared to pea protein. In many of our patients, we will supplement anywhere between 20-100 grams of additional protein to their diet, along with essential amino acids.
Stress and Impact on Tendon and Ligament Injury Recovery
Along with diet comes stress. Some of these horses are stressed, physiologically, as a result of a poor nutrition program. Others are just highly stressed, due to long term stall confinement or having to contend with ongoing pain. Many owners can attest to this fact, as they have to contend with an unruly horse and attempt to hand walk them intermittently during recovery. This stress component is huge, and the stress response in the horse will impair tissue healing due to often increased circulating levels of cortisol. The stress response must be altered for healing to occur. Sometimes this is easily managed by simple turnout, even in a small arena. If the stress response is still present and a major player, then you can attempt to alter it via adaptogen herbs. You don’t want to use sedatives, as many do, as this is not a solution and those sedatives further alter other cellular patterns and even digestion. Your goal is to modulate that stress response and adaptogens allow us to do just that.
There are many adaptogen herbs, and they demonstrate the ability to impact the stress response and the hypothalamic-adrenal axis. Ashwaghanda root extract is one of my first choices and does benefit many horses, however, for some it can be somewhat drying and make matters worse. Other adaptogen herbs include Eleutherococcus, Schisandra, Hawthorne, Asparagus, Bacopa, and many mushrooms which act as secondary adaptogens. I tend to use these adaptogens in combination, for synergistic benefits. If one is too drying for some reason, it will often be off-set by another herb.
Foot Balance and Influence on Tendon Recovery in the Horse
Foot balance becomes the next area to address and in almost all these cases, especially the chronic ones, there is an existing foot imbalance present. That imbalance could be the primary problem, or it could be secondary due to compensation. Either way, the feet need to be assessed with shoes off, determining heel to toe ratio, center point of the foot, break-over, medial-lateral balance, and then corrected. In most of our suspensory cases, the horses have a medial-lateral imbalance present. In many cases of tendon injuries, there is an under-run heel and elongated toe. Once these are corrected or better managed, the stress placed upon the structure is relieved, and healing is now encouraged. Often, in many of our patients, just this simple foot correction, along with diet and stress management, are enough to turn them around in a matter of a couple of weeks.
Inflammation and Recovery from Tendon and Ligament Injury
The other main area to focus on is the process of inflammation. Most of these patients have been on anti-inflammatories, mainly NSAIDs, for months if not years. Those medications are good for some cases, but long term they pose many problems regarding side effects. That class of medications does impact the inflammatory process, but in a restricted and isolated way, mainly by inhibiting COX production and prostaglandin production. This is good on some levels, but the inflammatory process is much more complex than this, having many more arms in the game than just COX and prostaglandins.
Inflammation is a complex cellular process, and to encourage proper healing, it needs to be controlled, not completely inhibited, which many of these medications do. We ideally want to modify the entire set of pathways, not just one or two isolated events. Currently, we do not have medications at our disposal to accomplish such a feat, and thus, we rely on nutrition and herbs. Whole foods, due to existing co-factors and phytochemical present, not only provide nutrient provision, but can also impact that inflammatory process. You don’t get that benefit by feeding a low-quality hay and then using a synthetic vitamin-mineral supplement.
Herbs are potent modulators of the inflammatory process, with many having hundreds of research papers to support their usage. Most of these herbs impact the inflammatory process at the root, which then modulates down ward pathways and cytokine production. Essentially, this allows us to manage that inflammatory process on a much higher level than traditional medications. Some of my favorite herbs include Turmeric (Curcumin), Boswellia, and Resveratrol. There are countless others, but these are the ones I focus on personally. The one thing that I can say regarding these herbs is that dosage and form can vary significantly from one patient to the other. Some patients require very high doses (5 grams or higher), while others require less. In all cases, they are used in combination with one another to gain synergism and dosage reduction. In my experience, one major reason why most owners fail to achieve benefit from herbs is improper dosage.
Exercise and Tendon or Ligament Recovery
The last area of discussion for most owners and veterinarians is exercise. In the acute patient, meaning the injury just happened, I am more inclined to reduce activity for a week to 10 days. This is dependent upon that patient. If they stall rest comfortably and maintain peace, then we go with that. If they get hyper-excited, pace and weave, then we go with a small paddock turnout. That excited patient will likely do more damage to the tendon or ligament under stall arrest than they will if turned out. Again, you must keep in mind the stress factor. Are you encouraging it or reducing it?
In the chronic cases, they are placed on turnout. It makes no sense in my mind to confine a horse that has likely been on confinement for 6 months or more. That injury is not acute but is chronic. The more confinement, the more scar tissue and the more inhibition of movement. I want to see them moving, even if it is a small paddock. More movement, more circulation, more stretching, and the more diffusion of nutrients.
This regimen of turnout, diet, stress management, and herbal supplementation is continued for 2-3 weeks with the horse being monitored almost daily. The feet are addressed and maintained about every 2 weeks. As the lameness improves and the horse regains comfort, then more exercise is put into place. Most will quickly move to light ground work, trotting on a lunge line or free lunge in a small arena. Again, they are monitored. How are they responding? Is the lameness made worse by the exercise? If so, we back off slightly but continue to move forward as well. You have to remember that in most cases of chronic injury, there is scar tissue that has been established. This tissue is inhibiting movement and stretching of that structure. In most, with exercise, there will be tearing of the tissue as it stretches. This is desired, however, as the tearing occurs, it will elicit and inflammatory reaction in the body. More pain and potentially more swelling. This is where our management program comes into play, attempting to manage that inflammatory response for a better recovery. In some, we will ice post exercise, others we may cold hose, some we will apply a poultice if needed. In most however, it is simple management through diet and supplementation.
As we progress with their exercise regimen, the horse quickly adapts if all factors are put into place. The tendon remodels, stretches, and heals. Soundness is then often achieved in a matter of a month or more. A high percentage of the horses maintain a swollen tendon cosmetically, but internally, the structure is sound, and solid. Most of these horses regain full soundness and are training at the same level as pre-injury. I also believe that most could go to higher levels with no fear of re-injury, if all factors are kept into play. Really, the lack of those factors is likely what opened the door for the injury.
A tendon or ligament injury is to be expected if you are managing horses, but with the right approach, the recovery process should be smooth and complete. They can regain normal function in the long term, and the recovery should not be frustrating or time consuming. Just try to remember not to focus just on the tendon or ligament injury. Keep in mind that there are often other players in that lameness condition, and when you address the whole horse, the body can heal.
Author: Tom Schell, D.V.M., CVCH, CHN