Tendon injuries are one of the most common injuries in the athletic horse. A summary of work presented at the IAVRPT symposium by Dr. Lesley Goff Tendon injuries.. Something we all dread but also something most of us have seen and most physical therapists have worked with.
They are one of the most common causes of lameness in the performance horse and there are various methods of treatment - however, in reality very little is known about tendon rehabilitation and it’s actually poorly researched.
So how do we know the best way to help a horse rehab after a tendon injury?
And furthermore.. Do we need to fix tendons..? Should our focus be on controlling pain and if a tendon does not have 100% function - does that matter?
Dr. Lesley Goff gave her expert knowledge at the International Association of Veterinary Rehabilitation and Physical Therapy symposium, helping us to figure out exactly what we should be doing to help our equine friends.
What are tendons - tendons are thick string-like tissue that connects muscles to bone.
Tendonopathy occurs when you injure or overuse a tendon - it’s a fairly broad term for any tendon condition that causes swelling and/or pain. It can be the degeneration of the tendon fibers.
Exercise in a correct and healthy way can promote tendon remodeling - this is the tendon improving itself and taking the strain of what it’s being asked to do.
This leads to long-term structural and functional improvements.
Tendon Injury in Equine Athletes
The equine Superficial Digital Flexor Tendon (SDFT) injury is one of the most common causes of lameness in the performance horse (O’brien et al 2021).
Tendons take a long time to heal, and that’s if they ever go back to ‘normal’ (which they probably won’t!).
Tendon injuries usually take a minimum of 3-4 months to recover.
It’s also highly dependent on the individual horse.
The question is - can we prevent tendon injury or tendinopathy from occurring?
Achilles tendon - Human
So far - much more research has been carried out on the human Achilles tendon than on the SDFT which comparitively is really useful to look at when we’re trying to come up with a horse tendon injury rehab plan.
In humans - Achilles tendinopathy isn’t that common with only 6% of people suffering from it in our general population. Although there is a higher instance of Achilles tendon injury in athletes.
Unfortunately, this means that research into tendon rehabilitation is fairly underfunded and therefore limited as it’s not considered to be serious enough or life-threatening in any way.
Achilles and SDFT
It’s great to compare the human Achilles tendon with the SDFT as both tendons are locomotor, energy-storing tendons.
They have similar physiology and similar pathology (typical presentation and behavior) for tendinopathy.
In both horses and humans, the pathology of tendinopathy starts with microdamage.
Tendons have low vascularisation (low blood flow) and microdamage doesn’t always manifest itself as pain - this means that the microdamage goes unnoticed until tendinopathy (or a worse injury) becomes apparent.
This is typical of the Equine SDFT injury that many of us have witnessed - the horse is seemingly fine one day and has a catastrophic tendon injury the next - a bowed tendon.
This isn’t the product of a one-day injury - it’s microdamage that has built up over time from repetitive action and overuse.
Factors that contribute to tendon injury are common to humans and horses.
These factors are:
- Adverse mechanical load - putting too much strain on a tendon
- Insufficient recovery time - working a tendon when it’s still remodeling from the last phase of work
- Age - older horses are more likely to sustain a tendon injury due to less elastin that allows the tendon to stretch and less fibromodulin - an important protein that participates in the alignment of collagen fibers. This all means that an older horse has less ability to recover from overload, will suffer from increased stiffness and has less ability to recover from fatigue.
- Dysfunction that may have been occurring prior to the injury - such as conformational abnormality or poor shoeing.
There are different stages of recovery when we’re looking at equine tendon injury rehabilitation.
Unfortunately, there is no clear single approach - no one size fits all. And most of all, no one is really sure how to heal tendons and ligaments faster.
Although rest may be vital when the pain of a tendon injury is acute - it can then be contraindicated as a treatment method.
Rest does result in an immediate decrease in pain, BUT, return to movement will increase pain and it will also affect muscle power, causing muscle to decrease in addition to ultimately weakening the tendon.
A tendon does best when it’s moving as this encourages the fibers to arrange themselves into alignment and also stimulates re-modeling, even after an injury, in order to cope with the movement it's being asked to do.
An exercise-based equine tendon injury rehabilitation is the most important intervention in the management of equine tendinopathy.
Exercise should form the core of the therapy, which should then be built upon using other methods that reduce pain during the healing process.
The best kind of exercise to rehabilitate tendons in humans has been found to be isometric muscle contractions - these are the muscle contractions for maintaining posture.
The question is - how do we achieve these in equine tendon injury rehabilitation? Horses are designed to sleep standing up and use very low muscle contractions to achieve this - comparatively to humans who actively use muscle to maintain posture.
It’s been suggested that we could experiment with strapping weights to horses' legs or perhaps just lifting a contralateral limb in order to activate the affected leg’s muscles.
It’s important to notice if pain or stiffness increases as this means that the exercise load in your rehabilitation is too much.
How do we assess pain in horses? - generally through lameness.
Stage one of recovery - How to start horse tendon injury rehab.
Aim - Reduce pain/no compression
Time 1-4 weeks
This is the acute phase where box rest may be temporarily crucial to control pain.
A vet will ultrasound the injury and decide if therapy such as laser treatment or PRP (plasma Rich Platelets) is appropriate.
Bute may be used but it’s not completely understood if this has an adverse effect on tendon healing.
Calling the farrier is very important - a shoe with a raised heel could help but this will be short-term (a very few days) and may not be appropriate at all.
Introduce hand walking on a level surface.
No compression!! Bandaging or compressing the tendon doesn’t help at this stage!
In fact, it probably just causes more discomfort initially and importantly we don’t want the tendon to heat up as this could cause more damage.
Ice is a really interesting one, it has a vasoconstriction effect for the first 5 minutes but after that causes vasodilation! So really we should remove ice after 5 minutes if we are aiming to constrict blood to an area
It’s not understood whether applying ice has a positive effect or not in the acute phase of tendon injury.
Definitely best to talk to a vet in detail about whether icing is the best course of action in acute tendon injury.
Stage 2 of recovery
Aim - Keep moving/no compression
Time - up to 12 weeks
It’s really important in equine tendon rehabilitation to get that injured tendon moving - but this has got to be controlled and allow time for the tendon to complete its remodeling phase in between bouts of movement.
This could include short walks in hand. Walking over different terrain, such as tarmac, grass and arena surface.
This exercise can be incrementally built up.
Stage 3 of recovery
Aim - Faster and more movement. Increase the range of movement and add compression.
Time - 12 weeks onwards up to when the individual horse is ready to move on!
So finally we’re allowed to add a compression bandage as this will now actually act as support to the tendon.
Now we can increase activity and introduce things into the horse tendon injury rehab plan that put more force on the tendon and stretch it to more of its potential.
For example, introducing long walks and eventually periods of trot and canter.
Remember that an increase in pain or stiffness means that the workload has been too much.
Stage 4 of recovery -
Aim - Sport-specific loading and adding compression
Time - up to 52 weeks!
We are still using a compression bandage to support the tendon and we’re starting to look at introducing ‘normal’ activity back into the horse's life - so basically returning to the job the horse once did.
At this stage therapy such as taping may help although this is again individual to each horse.
Remember - the horse may never return to its full potential after tendinopathy and a tendon may never go back to normal.
Key summary points
- Tendinopathy causes are not fully understood
- Treatment and management of tendinopathy are focused around an exercise-based rehabilitation program as well as interventions for pain
- Every horse tendon injury must be treated as an individual
- Therefore - every equine tendon rehab schedule needs to be tailored specifically to each horse and needs to be changed if lameness worsens
- It’s vital to assess any dysfunction that may have preceded the tendon injury such as conformation, shoeing or activities.
- DON’T rest the tendon
- DON’T expect the tendon to heal or ‘normalise’
- DO expect horse tendon injury rehab to take a long time.