Red Light Therapy for a Horse Check Ligament Injury: A Supportive Care Guide to ALDDFT Desmitis
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This guide explains why a check ligament injury is diagnosed by ultrasound rather than by looking at the leg — the swelling it produces in the upper cannon is routinely mistaken for a bowed tendon or a suspensory problem, and those three injuries carry different timelines and different prognoses. If your horse has a swollen leg and you are trying to work out what you are dealing with, our guide to whether red light therapy helps horse tendon injuries covers the wider soft tissue picture this sits inside.
The second core point overturns a common assumption: this is often an older horse's injury rather than a young athlete's. The check ligament degenerates with age — losing collagen quality and mechanical strength — which is why it turns up in cobs, natives and general-purpose horses in their teens as readily as in performance animals. It is also why a leg swelling on an older horse deserves the same scan a competition horse would get, not a wait-and-see. The confusion with a bowed tendon is so common that check ligament injuries in the upper cannon even have a nickname: "high bow."
The third point is the one that determines long-term outcome: adhesions. The check ligament is physically bound to the superficial flexor tendon by fibrous bundles, and when adhesions form between them the ligament loses its ability to glide — which predisposes the horse to injuring it again. So this guide covers the anatomy, why age matters, the sharp split between forelimb and hindlimb prognosis, what the ultrasound is really looking for, and the narrow, honest place supportive care occupies alongside months of controlled work.
The Short Answer
Red light therapy may have a modest supportive role in check ligament rehabilitation, but two things matter far more.
1. Ultrasound, not assumption. The check ligament sits deep between the suspensory ligament and the deep digital flexor tendon. A swelling in the upper cannon could be the check ligament, the superficial flexor tendon, or the suspensory — and they are managed differently.
2. Rest and controlled exercise do the healing. Veterinary sources describe the prognosis as guarded, particularly in chronic cases or where adhesions and flexural deformities are present, and note that recurrence is possible. No device changes the months this injury takes.
What the Check Ligament Actually Is
A safety strap for a tendon
Check ligaments — properly called accessory ligaments — are short bands of fibrous tissue that connect a flexor tendon to bone, limiting how far the tendon can stretch and providing passive support. Horses have two:
| Inferior (distal) check ligament | Superior check ligament | |
|---|---|---|
| Proper name | ALDDFT — accessory ligament of the deep digital flexor tendon | ALSDFT — accessory ligament of the superficial digital flexor tendon |
| Supports | Deep digital flexor tendon | Superficial digital flexor tendon |
| Frequency of injury | By far the more common | Less commonly reported |
Where the inferior check ligament runs
The ALDDFT arises from the palmar carpal ligament at the back of the knee, courses down the leg between the suspensory ligament and the deep digital flexor tendon, and inserts onto the dorsal surface of the deep digital flexor tendon in the mid-cannon region.
Its job is mechanical and specific: during exercise it shares the tensile load with the deep digital flexor tendon, passively carrying part of that load during maximal extension of the coffin and fetlock joints — preventing the tendon from being overstretched.
Why that job explains the injury
It is, in effect, a safety strap for a tendon. It fails when the tendon is asked for more than it can give — which is why previous or concurrent superficial digital flexor tendon injury may increase the stress on the check ligament. A horse with a tendon history carries additional risk here, and that connection is worth mentioning to your vet.
The Assumption Worth Overturning: This Is Often an Older Horse's Injury
The ligament weakens with age — measurably
Most soft tissue injury articles are written about performance horses. This one deserves a different framing, because the mechanism is partly degenerative.
Degenerative changes in the check ligament related to increasing age lead to a decreasing amount of fibrillar collagen and fewer large collagen fibres, which decreases the mechanical properties of the ligament and predisposes it to injury.
And once the ligament is compromised, it takes less to break it: repetitive microtrauma to these compromised ligaments may also lead to clinical desmitis. The injury does not require a dramatic moment — an ordinary workload on an ageing ligament will do.
What the case series show
A retrospective study of hindlimb check ligament cases makes the demographic strikingly clear. Of 23 horses: twenty were used for general purposes rather than competition, the group comprised ten cobs, five British native-breed ponies and eight horses of various larger breeds, and the mean age was 12 years.
The forelimb presentation is different
In the forelimb the classic story is acute. In a series of 27 horses, twenty became lame suddenly during a work period, and most developed swelling within 24 hours of exercise. In four horses the first sign noticed was localised swelling in the upper cannon rather than lameness. So the picture ranges from "he came up lame in the school" to "I found a lump this morning."
The practical consequence: a swollen upper cannon on a fifteen-year-old cob in light work is not automatically a knock or a filled leg. Given what age does to this ligament, it deserves the same ultrasound a competition horse would get. Assuming an older horse's leg swelling is "just wear and tear" is how a treatable acute injury becomes a chronic one.
Why Ultrasound Is Not Optional
Three structures occupy the upper cannon region, and a swelling there can come from any of them.
| Structure | What it is | Why it gets confused |
|---|---|---|
| Check ligament (ALDDFT) | Accessory ligament supporting the DDFT | Swelling sits high on the cannon — nicknamed "high bow" |
| Superficial digital flexor tendon | The classic bowed tendon | Similar external appearance, different structure and timeline |
| Suspensory ligament | Runs alongside the check ligament | Adjacent anatomy; different prognosis and rehabilitation |
Three injuries, one lump
The check ligament runs between the suspensory ligament and the deep digital flexor tendon — it is sandwiched between the two structures it is most often mistaken for. From the outside you are looking at swelling; from the inside these are different injuries with different rehabilitation timelines and different prognoses.
The injury is confirmed by ultrasonographic examination. Not by palpation, not by location, and not by how much it looks like a bow.
Depth is part of why this matters for anyone considering supportive therapy too. The check ligament is not a superficial structure — it lies deep in the limb between other soft tissues, which is a different proposition from the tissue directly under the skin. Our guide to how deep red light penetrates a horse's leg sets out what that means in practice.
The Factor That Drives Recurrence: Adhesions
The check ligament is physically bound to the tendon beside it
This is the feature that makes check ligament injury behave differently from other ligament injuries, and it is anatomical.
The check ligament and the superficial digital flexor tendon are bound together by fibrous bundles. It is this connection which predisposes the development of adhesions between both structures in cases of severe lesions and inflammation.
Why that matters: true adhesion formation may affect the normal gliding function of the check ligament, thus predisposing these horses to further injury. A ligament that cannot glide is a ligament being loaded wrongly with every stride.
The follow-up data supports the concern — in one large case study, one third of horses with adhesion formation had recurrence of the injury during the follow-up period.
What this means for how you manage the rehab
It reframes what the controlled exercise programme is for. It is not only about loading the healing tissue appropriately — it is also about maintaining the ligament's ability to move relative to the structures around it. That is a strong argument for following your vet's programme precisely rather than resting longer "to be safe," and it is a question worth asking directly: does the follow-up ultrasound show adhesions?
Prognosis: Better Than Feared, Worse Than Advertised
The honest picture requires separating simple acute injuries from chronic and complicated ones — because the difference between them is large.
Uncomplicated forelimb cases: genuinely encouraging
In a series of horses with straightforward check ligament desmitis, ten of thirteen resumed full work within three to nine months of the onset of clinical signs — and without recurrence of clinical signs during a follow-up period of nine months to four years. That is a good outcome by any soft tissue standard.
The overall veterinary view: guarded
Against that optimism, the broader assessment is more cautious. Veterinary sources describe the prognosis as guarded, especially in chronic cases or where adhesions and flexural deformities are present, and state plainly that recurrence is possible. Both statements are true at once — which is why the specifics of your horse's ultrasound matter more than any general figure.
Hindlimb: the split is dramatic
A study of 23 hindlimb cases found two distinct clinical patterns with very different outcomes:
| Presentation | Outcome |
|---|---|
| Traumatic, acute-onset lameness | 73% returned to full function — favourable prognosis, most returned to previous work |
| Insidious or sudden postural abnormality | 90% remained lame |
Two horses, the same ligament, opposite futures — separated by how the problem presented. That is the single strongest argument for a proper veterinary assessment rather than a general prognosis from an article.
Treatment: What the Evidence Actually Shows
A retrospective study of 91 horses with forelimb check ligament desmitis gives a useful picture of how these cases are managed in practice:
- Rest and controlled exercise — the foundation, and the treatment the majority receive.
- Intra-lesional injection (18%) — platelet-rich plasma, mesenchymal stem cells or corticosteroids, in combination with rest.
- Extracorporeal shockwave or therapeutic ultrasound (7%) — combined with rest and controlled exercise.
- Desmotomy or desmectomy (4%) — surgical transection or removal, reserved for selected cases.
Note the proportions
The interventional treatments — injections, shockwave, surgery — account for a minority of cases. The bulk of check ligament management is rest and controlled exercise, and that remains true no matter what adjuncts are added around it. Notably, horses with ultrasonographic evidence of adhesions were more likely to receive the more aggressive interventions, reflecting clinical concern about that specific finding.
Desmotomy: two completely different operations under one name
Check ligament desmotomy — surgically cutting the ligament — is used for two entirely different purposes, and confusing them causes real misunderstanding:
| Purpose | Details |
|---|---|
| Correcting flexural deformity in young horses | Used to correct flexural deformity of the coffin and fetlock joints. Timing matters: surgery at a median age of 6 months produced more horses with normal foot conformation than surgery at a median of 12 months. |
| Treating chronic desmitis in mature horses | In mature horses, desmotomy resulted in successful return to intended use in most horses with check ligament desmitis (75%). Modern ultrasound-guided technique limits incision size and reduces scarring compared with open surgery. |
Both are veterinary decisions, and the second is generally reserved for chronic cases that have not responded to conservative management — particularly where adhesions are present. Complications of the open approach can include incisional swelling, dehiscence and postoperative scarring, which is why the ultrasound-guided technique has gained ground.
So Where Does Red Light Therapy Honestly Fit?
In a supporting role, in the right phase, alongside a programme that does the actual work.
What it cannot do
- It does not shorten ligament healing. Three to nine months for an uncomplicated case is the biology, not a target to beat.
- It does not prevent or resolve adhesions. Controlled movement under veterinary guidance is what maintains gliding function.
- It does not diagnose. Nothing about applying a device tells you whether you are dealing with the check ligament, the flexor tendon or the suspensory.
- It does not correct a flexural deformity, which is a surgical question.
The specific risk with this injury
Check ligament injury has a long, unglamorous rehabilitation measured in months of controlled exercise, and the temptation is to look for something that feels more active than waiting.
The danger is not that a supportive therapy fails — it is that it creates the sense that progress is being made and makes an early return to work easier to justify. With an injury where recurrence is possible and adhesions predispose to re-injury, that is exactly the wrong pressure to introduce.
We would rather you spent the money on the follow-up ultrasound that tells you whether the ligament is actually ready.
The legitimate role
If your vet has scanned the leg, established the diagnosis and grade, and set a rehabilitation programme, then supportive comfort care for the limb may have a modest place within it — if your vet agrees it helps your individual horse. For positioning over the cannon region, our red light therapy leg boots are designed to wrap that area. Bear in mind the depth point above: this ligament sits deep between other structures, so what light reaches most readily is the tissue nearer the surface.
The question to ask your vet is not "should I use red light therapy?" but "what does the follow-up scan show, and is the horse ready for the next stage of work?" The answer to that determines the outcome. Everything else is around the edges.
Conclusion: Scan It, Then Do the Months
A check ligament injury is defined by three things most owners are never told. It is diagnosed by ultrasound, not by appearance — the ligament runs between the suspensory and the deep flexor tendon, and the swelling it produces is routinely mistaken for a bowed tendon, which is why the nickname "high bow" exists. It is often an older horse's problem, because the ligament loses collagen quality and mechanical strength with age, and repetitive microtrauma then finishes the job. And it is shaped by adhesions: the ligament is bound to the superficial flexor tendon by fibrous bundles, and when adhesions form, gliding is lost and re-injury follows — one third of horses with adhesions had a recurrence.
The prognosis deserves the same honesty. Uncomplicated forelimb cases do well — ten of thirteen back in full work within three to nine months, with no recurrence over a follow-up of up to four years. But the broader veterinary view is guarded, particularly with chronic cases, adhesions or flexural deformity, and hindlimb outcomes split sharply: 73% recovered from traumatic acute cases, while 90% of postural-onset cases remained lame. Your horse's scan, not an average, tells you which story you are in.
Red light therapy does not shorten that timeline, resolve adhesions or replace the scan. Its honest place is modest comfort support inside a vet-led rehabilitation programme — and the thing that actually determines whether your horse comes back sound is the months of controlled exercise, done properly, checked by ultrasound. Get the scan. Do the months. Ask the vet before the horse asks for more work than the ligament can give.
Frequently Asked Questions
Can red light therapy help a horse check ligament injury?
It may have a supportive role within a vet-directed rehabilitation plan, and the tissue is reachable, but two things matter far more than the device. First, the diagnosis has to come from ultrasound. The check ligament sits deep between the suspensory ligament and the deep digital flexor tendon, and the swelling it produces in the upper cannon region is easily mistaken for a bowed tendon or a suspensory problem — three injuries with different rehabilitation timelines and different prognoses. Second, the outcome depends overwhelmingly on rest and controlled exercise, not on any adjunct. Veterinary sources describe the prognosis as guarded, particularly in chronic cases or where adhesions and flexural deformities are present, and note that recurrence is possible. So the honest framing is this: get the ultrasound, follow the rehabilitation programme your vet sets, and ask whether supportive comfort care has a place alongside it. Light does not shorten ligament healing, and nothing about a device changes the months of controlled work this injury requires.
What is the check ligament in a horse?
Check ligaments, properly called accessory ligaments, are short bands of fibrous tissue that connect a flexor tendon to bone, limiting how far the tendon can stretch and providing passive support. Horses have two: the inferior or distal check ligament, which is the accessory ligament of the deep digital flexor tendon and is by far the more commonly injured, and the superior check ligament, which is the accessory ligament of the superficial digital flexor tendon. The inferior check ligament arises from the palmar carpal ligament at the back of the knee, runs down between the suspensory ligament and the deep digital flexor tendon, and inserts onto the deep digital flexor tendon in the mid-cannon region. Its job during exercise is to share the tensile load with the deep digital flexor tendon, passively carrying part of the load during maximal extension of the fetlock and coffin joints and preventing the tendon being overstretched. In effect it is a safety strap for a tendon — which is why it fails when that tendon is asked for more than it can give.
Is a check ligament injury the same as a bowed tendon?
No, though they are frequently confused, and the confusion has a name. Check ligament injuries occurring in the upper cannon region are sometimes called high-bow injuries, because the swelling appears higher up the leg than the classic bowed tendon and can look similar from the outside. But the structures are different: a bowed tendon is injury to the superficial digital flexor tendon itself, while a check ligament injury involves the accessory ligament that supports the deep digital flexor tendon. The distinction matters practically because the rehabilitation timelines, the risk of adhesions and the prognosis are not the same. There is also a real connection between them worth knowing: previous or concurrent superficial digital flexor tendon injury may increase the stress on the check ligament, so a horse with a history of tendon injury carries additional risk. Only ultrasound separates these reliably, which is why a swelling in the upper cannon should be scanned rather than assumed.
Which horses get check ligament injuries?
More often than people expect, older horses in ordinary work rather than young racehorses. There is a specific reason for this: degenerative changes in the check ligament related to increasing age lead to a decreasing amount of fibrillar collagen and fewer large collagen fibres, which reduces the mechanical properties of the ligament and predisposes it to injury. In other words the ligament weakens with age, and repetitive microtrauma to an already compromised ligament can then produce clinical desmitis. A retrospective study of hindlimb cases illustrates the pattern clearly: of 23 horses, most were used for general purposes rather than competition, the group included ten cobs and five British native-breed ponies, and the mean age was twelve years. The classic presentation in the forelimb is different again — a horse that goes suddenly lame during work, with swelling developing within 24 hours of exercise. So this is not exclusively an athlete's injury, and an older horse with a swollen upper cannon deserves the same investigation a performance horse would get.
What is the prognosis for a check ligament injury?
Considerably better for simple acute cases than for chronic ones, and the presence of adhesions is the factor that changes everything. For uncomplicated forelimb desmitis the outlook is genuinely encouraging: in one series, ten of thirteen horses with uncomplicated check ligament desmitis resumed full work within three to nine months of the onset of signs, without recurrence during a follow-up period of nine months to four years. Against that, veterinary sources describe the overall prognosis as guarded, especially in chronic cases or where adhesions and flexural deformities are present, and state plainly that recurrence is possible. Hindlimb cases split sharply by presentation: in one study of 23 horses, 73% of those with traumatically induced acute lameness returned to full function, while 90% of those presenting with postural abnormality remained lame. Adhesions matter because the check ligament is bound to the superficial flexor tendon by fibrous bundles, and adhesions between them disrupt normal gliding — one third of horses with adhesion formation experienced recurrence.
