Where do tendon injuries come from?
While tendon injuries often seem to come out of the blue, this is actually rarely the case. Most often, tendons get injured as a result of micro trauma accumulated over time.
When dealing with tendon injuries, we must not forget that the tendon is not an independent unit – it is a part of the muscle.
Just the idea of a tendon injury is enough to make a horse owner shudder. These issues are very common in horses and they can be very frustrating, as they usually need a very long time to heal properly. And even once they've healed, the new tissue is always going to be weaker than the original, which is obviously a very scary thought. So, as always, prevention is much, much better than cure. If we want to be proactive in reducing the chances of our horse getting a tendon injury, we have to understand why tendon injuries happen in the first place.
Very often, it will seem to come out of the blue. The horse is fine on day and the next he hobbles out of his stall. Because tendon injuries occur seemingly out of nowhere, it might look like there is no way of preventing or predicting them. But that is not the case. Most tendons get injured because of micro damage accumulating over a longer period of time. We tend to think of tendons as independent units, but in reality, they are far from independent. Tendons are what connects muscle to bone, so the long flexor tendons are actually just the continuation of the flexor muscles higher up the leg. We always talk about how tendons act as elastic springs that enable the horse to save energy during locomotion. But did you know that the majority of this elasticity actually comes from the muscle, not the tendon? So, it's actually the muscle that provides the energy-efficient movement, not so much the tendon itself.
We see now how the functionality of the tendon is actually tightly connected to the functionality of the muscle. If the muscle isn't working optimally, the tendon will have to work harder, which puts it at risk of injury. So now the question becomes, when are the flexor muscles not working optimally? Muscles depend on each other for healthy locomotion so dysfunction in one muscle group will always cause dysfunction in the neighbouring muscles in the long run. Very often the reason why the flexor muscles aren't working like they should is dysfunction in the thoracic sling – the muscles that attach the front limb to the body. These muscles act as nature's shock absorbers if they are well developed and the horse knows how to use them. Unfortunately, weak thoracic sling muscles are very common in ridden horses. A weak thoracic sling means less hock absorption, which means the flexor muscles will have to work harder. This in time will cause them and the fascia around them to tighten, limiting their elastic potential. This will in turn put more strain on the tendons, causing them to get closer and closer to breaking point. If at that point the horse takes a bad step or he is worked just a little too much past the point of fatigue, injury can occur. But the bad step was just the straw that broke the camel's back, not the actual cause of the problem. The problem started way earlier, when we failed to notice that the horse has a weak thoracic sling.
A weak thoracic sling will not be able to provide optimal shock absorption which will put too much strain on the tendons.
Of course, a weak thoracic sling isn't the only cause of tendon injuries. And of course, tendon injuries can occur in horses with well-developed thoracic sling as well. The likelihood of them occurring is just way smaller. Another big cause of tendon injuries lies on the other end of the leg – hoof balance can have a negative impact on tendons as well. More on that next week.