Red Light Therapy for Sidebone in Horses: A Supportive Care Guide to Ossified Collateral Cartilages
Share
This guide explains why sidebone in horses is usually an incidental finding rather than a diagnosis — around 80% of horses show it on radiographs and most stay sound for their entire careers — and why that single fact should shape every decision you make about it, including whether red light therapy has any role at all. Sidebone sits alongside the other conditions covered in our guide to horse hoof problems, but it behaves very differently from most of them.
Here is the core position we will defend throughout, stated plainly because it matters more than any product: red light therapy cannot treat sidebone. Ossified cartilage does not turn back into cartilage, and the collateral cartilages sit inside the hoof capsule where light physically cannot reach — a limit explained in detail in our red light therapy penetration depth guide. Neither of those is the biggest concern, though.
The biggest concern is this: because sidebone is so often incidental, a lame horse with sidebone on X-ray usually has a different, real problem elsewhere in the foot. Reaching for any therapy aimed at "the sidebone" risks treating a decoy while the actual cause of lameness continues unaddressed. So this guide covers what sidebone genuinely is, when it truly matters, what to do about a prepurchase finding, and the narrow, honest place supportive therapy occupies — after a diagnosis, never instead of one.
The Short Answer
Red light therapy does not treat sidebone. The condition is cartilage turning into bone, and there is no known treatment that resolves or reverses it — veterinary or otherwise. Light does not reverse ossification, and it does not penetrate the hoof capsule to reach the collateral cartilages in the first place.
More importantly: in most horses, sidebone doesn't need treating at all. Veterinary guidance is explicit that there is no need to treat subclinical ossification. And if your horse is lame, the correct sequence is a full veterinary workup that excludes all other causes before blaming the sidebone — because statistically, something else is usually to blame.
What Sidebone Actually Is
The anatomy: flexible plates that turn to bone
Sidebone is the ossification — hardening into bone — of the collateral cartilages of the hoof. Those cartilages, also called the ungual cartilages, are paired flexible sheets that project from the back of the wings of the coffin bone, inside the heel of the foot.
In a healthy horse, they are firm, rubbery, flexible ridges that you can feel just above the coronet. They do two jobs: hold the shape of the heel bulbs, and help the foot absorb concussion. In sidebone, those springy plates gradually calcify into rigid bone.
How the ossification progresses
Ossification usually starts at the base of the cartilage and extends upward, though it can also begin from a separate centre of ossification. It is commonly more extensive in the lateral (outside) cartilage than the medial (inside) one — which is why the outside of the front foot is where it is most often described.
Which horses get it
| Factor | What's known |
|---|---|
| Which feet | Front feet almost exclusively — it rarely occurs in the hind feet |
| Breed & type | Far more common in heavier horses: drafts, draft crosses, warmbloods, cob types |
| Age | More common in older horses — mild ossification is considered part of normal ageing |
| Conformation | Pigeon-toed conformation is commonly implicated, probably through unequal loading of the foot |
| Concussion | Believed to result from concussive forces travelling through the foot during weight-bearing; working surfaces matter |
| Foot balance | Long-term foot imbalance plays a role, as does poor limb conformation |
| Exact cause | Unknown — trauma, weight, breed and possible genetic factors all thought to contribute |
The Fact That Changes Everything: 80% Have It, Most Stay Sound
Sidebone is usually a finding, not a problem
Around 80% of horses show radiographic sidebone, and most remain sound throughout their careers.
Veterinary sources are consistent and blunt about what follows from that: sidebone is rarely the primary source of lameness in horses. The ossification is usually an incidental finding on physical examination or radiographic evaluation of the foot.
Which leads to the instruction that should govern every lame horse with this finding: in horses with lameness, all other causes should be excluded before the lameness is attributed to sidebone.
And for the horses that aren't lame at all: there is no need to treat subclinical ossification of the collateral cartilages. Nothing. No device, no supplement, no protocol.
This is why a sidebone diagnosis frightens owners far more than it should. The word sounds structural and permanent — and it is permanent — but permanence is not the same as significance. An unchangeable finding that most horses carry without consequence is not the same as a disease.
The Decoy Problem: Why Treating Sidebone Can Be Actively Harmful
If sidebone is usually incidental, then a lame horse with sidebone on X-ray has an obvious trap waiting: the visible finding is not the cause, and looking at it stops you looking further.
Sidebone is frequently mistaken for the real problem
Veterinary literature is direct about this: sidebones may accompany other lameness conditions of the palmar heel region — for example navicular syndrome — and may be mistaken for the cause.
That heel region is crowded. Advanced imaging is sometimes needed precisely because MRI may be required to identify the specific soft tissue injuries in the hoof that are the real cause of the lameness.
So the honest risk of "treating the sidebone" isn't that a device wastes money. It's that time spent treating a decoy is time the genuine problem keeps progressing.
Why nerve blocks alone don't settle it
Even the diagnostic tools have limits worth understanding. A nerve block of the heel region will numb pain from the collateral cartilage — but it also desensitises numerous other structures, including the seat of corn, frog, digital cushion, navicular bone, navicular bursa and part of the coffin joint. It can confirm the region causing lameness, but it won't identify which structure. That's why your vet may need radiographs, ultrasound, or advanced imaging on top.
If the lameness is localised to the foot, our guide to red light therapy for navicular syndrome covers the condition most often sitting behind a heel-region lameness that gets blamed on sidebone.
When Sidebone Genuinely Does Matter
None of the above means sidebone is always harmless. There are specific, recognised situations where it becomes clinically real — and every one is a veterinary diagnosis, not a home judgement.
- Fracture of an ossified cartilage. A fractured sidebone can cause sudden and obvious lameness, with local heat, swelling and pain on palpation. Your vet must distinguish a true fracture from a separate ossification centre on radiographs — they can look similar.
- Loss of shock absorption. Horses with extensive ossification may lose much of the foot's normal shock-absorbing function, which can limit performance and potentially cause lameness.
- Associated injuries. Substantially ossified cartilages are associated with injury to the collateral ligament of the coffin joint or to the coffin bone itself, and large sidebones have been linked to certain coffin bone fractures.
- Quittor — infection of the cartilages. A significant cause of lameness that needs prompt diagnosis and treatment to prevent further tissue damage. This is an infection, and infections are never a job for light therapy.
- Palmar hyperostosis. An uncommon finding where only the back part of the cartilage mineralises, associated with lameness.
What these have in common: not one of them can be identified by an owner feeling the heel or reading an X-ray report. They require a lameness examination, imaging and veterinary interpretation. If your horse is lame, that is the pathway — regardless of what the word "sidebone" appears to explain.
Signs You Might Notice
- A firm, inflexible feel above the coronet. In extensively ossified cases, the lack of flexibility can be palpated immediately above the coronet at the back of the hoof, where normal cartilage feels rubbery and springy.
- Visible widening of the pastern region. If ossification is extensive, sidebones may appear as an enlargement of the pastern's side-to-side dimensions.
- Usually no pain on pressure. Notably, pain is rarely elicited by digital pressure on a sidebone — which is itself a clue that it isn't the source of trouble.
- Sudden lameness with heat and swelling — the picture that suggests a fracture, and warrants a same-day vet call.
- Often nothing at all. The most common presentation is a horse that is completely sound, with sidebone discovered incidentally.
Sidebone at a Prepurchase Exam
This is where the anxiety concentrates, so it deserves a direct answer.
Veterinary sources are candid that the biggest difficulty with sidebone is deciding on its significance in a given case of lameness, and predicting whether a horse with the finding will go lame in future. That uncertainty is genuine, and no article — including this one — can remove it.
How to think about it sensibly
Given that around 80% of horses carry radiographic sidebone and most stay sound, treating the finding as automatically disqualifying would rule out a very large share of perfectly good horses. What matters is context: Is the horse sound now? Is the ossification mild or extensive? Is it symmetric or heavily one-sided? Is the foot balanced? What job will the horse do? Are there other findings alongside it?
A mild, symmetric finding in a sound heavy-breed horse means something entirely different from extensive unilateral ossification in a horse with a history of foot lameness. Ask your vet to interpret the finding in context, rather than reacting to the word.
What Actually Helps
Because the ossification cannot be reversed, management is about comfort, balance and prevention of further insult — not about undoing what has formed.
| Approach | What it does |
|---|---|
| No treatment (most cases) | There is no need to treat subclinical ossification. A sound horse with incidental sidebone needs monitoring, not intervention. |
| Hoof balance | Central. Regular trimming and shoeing to prevent imbalance and uneven weight-bearing, since long-term imbalance contributes to the condition. |
| Rest | Where sidebone is genuinely causing lameness, an extended period of rest may be advised by your vet. |
| Anti-inflammatory medication | Non-steroidal anti-inflammatories, prescribed by your vet, where the condition is causing pain. |
| Surfaces & workload | The surfaces a horse works on can affect development; reducing concussion is sensible management. |
| Surgery | Rarely needed. Prognosis is good unless the lameness requires surgery, in which case it becomes guarded. |
So Where Does Red Light Therapy Honestly Fit?
Narrowly, and only after a diagnosis — and with sidebone specifically, the honest answer is narrower than for most conditions.
Three reasons it isn't a sidebone treatment
1. It doesn't reverse ossification. There is no known treatment that resolves or reverses ossified collateral cartilages. That's not a limitation of light therapy — it's the nature of the condition.
2. It can't physically reach the cartilages. The collateral cartilages sit at the back of the coffin bone, largely enclosed by the hoof capsule. Red and near-infrared light are absorbed and scattered within millimetres of soft tissue and do not pass through hoof horn — the practical limits are set out in our wavelength and penetration depth guide.
3. Most sidebone needs no treatment at all. Applying anything to a finding that veterinary guidance says requires no treatment is, at best, effort spent on nothing.
The line that matters most here
Never let a device delay the search for the real cause. With sidebone the risk is unusually specific: the finding is visible, permanent and easy to blame, while the actual source of lameness — a collateral ligament, the navicular region, a coffin bone injury — may be invisible without advanced imaging.
A horse treated for "sidebone" is a horse not being investigated for what's actually wrong. We would rather you spent your money on the diagnostic workup than on anything we sell.
The genuinely narrow role: if your vet has completed a workup, identified a specific soft-tissue problem in the pastern or heel region that they consider appropriate for supportive care, and is running a management plan, then red light therapy may offer modest comfort support to that accessible soft tissue — never to the ossified cartilage itself, and never as a substitute for the plan. If you're exploring supportive options for the foot within such a plan, our red light therapy hoof boots are built for that supportive role, with the same caveat that applies throughout this article: diagnosis first.
Conclusion: A Finding, Not a Verdict
Sidebone is the most reassuring diagnosis that frightens owners most. Around 80% of horses show it on radiographs and the majority stay sound for their whole careers; veterinary guidance is clear that it is rarely the primary source of lameness, that the ossification is usually incidental, and that subclinical ossification needs no treatment. The permanence of the change is not the same as its significance.
Where it genuinely matters — a fractured ossified cartilage, extensive loss of shock absorption, associated coffin joint or coffin bone injury, or quittor — those are veterinary diagnoses reached through examination and imaging, not conclusions to draw at home. And in a lame horse, the professional standard is unambiguous: exclude every other cause before blaming the sidebone.
Red light therapy doesn't reverse ossification, doesn't penetrate the hoof capsule, and has no role in treating this condition. Its only honest place is modest comfort support for accessible soft tissue inside a vet-directed plan — after the diagnosis, never in place of it. If your horse is lame, spend on the workup first. That is where the answer lives, and a finding on a film is not it.
Frequently Asked Questions
Can red light therapy treat sidebone in horses?
No. Sidebone is the ossification of the collateral cartilages of the hoof — flexible cartilage turning into bone — and there is no known treatment that resolves or reverses that ossification, veterinary or otherwise. Light does not turn bone back into cartilage. There is also a physical barrier: the collateral cartilages sit at the back of the coffin bone within the heel of the foot, largely enclosed by the hoof capsule, and red and near-infrared light cannot penetrate hoof horn to reach them. But the most important reason to be cautious is different again. Sidebone is rarely the primary source of lameness and is usually an incidental radiographic finding, which means a lame horse with sidebone on X-ray very often has a different, real problem elsewhere in the foot. Using any device to treat the sidebone risks treating a decoy while the actual cause continues. If your horse is lame, the priority is a veterinary diagnosis, not a therapy.
What is sidebone in horses?
Sidebone is the hardening, or ossification, of the collateral cartilages of the hoof into bone. The collateral cartilages — also called the ungual cartilages — are paired flexible sheets that project from the back of the wings of the coffin bone inside the heel of the foot. In a normal horse they are firm, rubbery, flexible ridges you can feel above the coronet, and their job is to hold the shape of the heel bulbs and help absorb concussion. In sidebone, those springy plates gradually calcify into rigid bone. Ossification usually begins at the base of the cartilage and extends upward, and it is commonly more extensive in the lateral cartilage than the medial one. It affects the front feet almost exclusively and rarely occurs behind. It is far more common in heavier horses — draft breeds, draft crosses, warmbloods and cob types — and is more frequent in older horses, to the point that some degree of ossification is considered part of normal ageing.
Does sidebone cause lameness in horses?
Usually not. This is the single most important thing to understand about the condition. Around 80% of horses show radiographic sidebone and most remain sound throughout their careers, and veterinary sources are consistent that sidebone is rarely the primary source of lameness — the ossification is typically an incidental finding on physical or radiographic examination. Because of that, veterinary guidance is explicit that in a lame horse, all other causes should be excluded before the lameness is attributed to sidebone. There are genuine exceptions. A fracture of an already ossified cartilage can cause sudden, obvious lameness with local heat, swelling and pain on palpation. Very extensive ossification can reduce the foot's normal shock-absorbing function. Large sidebones have been associated with certain coffin bone fractures and with injury to the collateral ligaments of the coffin joint. And quittor — infection of the cartilages — is a significant cause of lameness needing prompt treatment. Those are vet-diagnosed situations, not assumptions to make at home.
Should I buy a horse with sidebone showing on prepurchase X-rays?
A sidebone finding alone is not a reason to walk away, but it is a reason to have a proper conversation with your vet about the whole horse. Given that around 80% of horses show radiographic sidebone and most stay sound for their whole careers, treating the finding as automatically disqualifying would rule out a great many perfectly good horses. Veterinary sources are candid that the hardest part of sidebone is judging its significance in an individual case and predicting whether a horse with the finding will go lame in future — that uncertainty is real and nobody can remove it. What matters is context: is the horse sound now, is the ossification mild or extensive, is the foot balanced, what is the horse's job going to be, and are there other findings alongside it? A mild, symmetric finding in a sound heavy-breed horse means something very different from extensive unilateral ossification in a horse with a history of foot lameness. Ask your vet to interpret it in that context rather than reacting to the word itself.
How is sidebone treated in horses?
In most cases it is not treated at all, because it does not need to be. Veterinary guidance states plainly that there is no need to treat subclinical ossification of the collateral cartilages, and there is no known treatment that resolves or reverses the ossification itself. Where sidebone genuinely is deemed the cause of lameness, management is conservative: rest, non-steroidal anti-inflammatory medication prescribed by your vet, and careful attention to hoof balance, since long-term foot imbalance and uneven loading are believed to contribute to the condition developing. Corrective trimming and shoeing to restore balance and reduce uneven weight-bearing are central, and an extended period of rest may be advised in an actively painful case. The overall prognosis for sidebone is good unless the nature of the lameness requires surgery, in which case it becomes more guarded. Every one of these decisions belongs with your vet and farrier working together on your individual horse.
