Physitis in Foals: Signs, Causes and What To Do

By Dr Duncan Houston

Physitis is one of those foal problems that can look mild at first, then become a much bigger concern if it is ignored.

A young horse may develop firm swelling above the fetlocks, knees, or hocks. The limbs may look “boxy” around the growth plates. Some foals stay bright and only mildly stiff. Others become lame, painful, or develop limb deviations if the growth plate is overloaded or damaged.

The difficult part is that physitis is often blamed on “growing pains,” but that phrase can make owners too relaxed. Physitis is common in fast-growing foals, but it is not something to dismiss. It means the growth plate is inflamed and the foal’s nutrition, exercise, body condition, conformation, and environment need to be reassessed.

The goal is not to stop growth. The goal is to make growth steadier, safer, and better supported.

Quick Answer

Physitis is inflammation of a growth plate in a young horse. It usually causes firm swelling, heat, pain, and sometimes lameness around areas such as the fetlocks, knees, hocks, or long pastern region. It is commonly linked with rapid growth, excess body weight, hard ground, excessive exercise, conformational loading, and nutritional imbalance. Most uncomplicated cases improve with controlled exercise, a balanced diet, careful weight and growth management, good hoof care, and veterinary monitoring, but severe pain, fever, marked lameness, limb deformity, or suspected infection needs urgent veterinary care. (Merck Veterinary Manual)

What Is Physitis?

Physitis means inflammation of the physis, which is the growth plate near the end of a developing bone.

Growth plates are areas where cartilage is gradually transformed into bone as the foal grows. These regions are active, delicate, and sensitive to overload. If the growth plate is stressed by too much body weight, rapid growth, hard ground, poor conformation, excessive exercise, or nutritional imbalance, it can become inflamed and swollen. (Merck Veterinary Manual)

Physitis is also sometimes called:

• Epiphysitis

• Physeal dysplasia

• Dysplasia of the growth plate

• Growth plate inflammation

“Epiphysitis” is still commonly used by horse people, but “physitis” is more anatomically accurate because the physis is the growth plate.

Where Does Physitis Usually Occur?

Physitis most commonly affects the growth plates near the lower ends of long bones.

Common sites include:

Location	What owners may notice
Above the fetlock	Firm swelling just above the joint, often in front limbs
Above the knee	Boxy swelling around the distal radius region
Above the hock	Swelling around the distal tibia region
Long pastern region	Swelling near the proximal first phalanx

Merck Veterinary Manual lists common sites as the distal radius, distal tibia, distal third metacarpal or metatarsal bone, and the proximal aspect of the first phalanx. (Merck Veterinary Manual)

In practice, owners most often notice the fetlock region first because it is easy to see and compare between limbs.

What Does Physitis Look Like?

Physitis can be mild or obvious.

Common signs include:

• Firm swelling around the growth plate

• Heat over the swollen area

• Pain when the area is pressed

• A “boxy” or enlarged appearance around the joint

• Mild stiffness

• Short, careful steps

• Lameness, especially in more painful cases

• Bilateral or symmetrical swelling

• Limb deviation if one side of the growth plate is affected more than the other

Merck describes physitis as heat, pain, and swelling around growth plates, sometimes with mild lameness and visible flaring that creates a typical boxy appearance. (Merck Veterinary Manual)

A key point: the swelling may look worse than the lameness. Some foals have obvious growth plate enlargement but only mild discomfort. Others are genuinely painful.

What Causes Physitis?

Physitis is usually multifactorial. That means it is rarely one simple cause.

Common contributors include:

• Rapid growth

• Excess body condition

• Heavy muscling in young stock

• High-energy diets

• Too much concentrate or sweet feed

• Mineral imbalance

• Calcium and phosphorus imbalance

• Excessive exercise

• Hard, dry ground

• Conformational defects

• Uneven loading of the limb

• Trauma

• Toxicosis in some cases

Merck lists possible causes as malnutrition, conformational defects, excessive exercise, obesity, and toxicosis, and notes that physitis probably results from overload of the growth plate area due to excessive loading, weakened bone or cartilage, or both. (Merck Veterinary Manual)

That is the practical veterinary message: physitis often happens when the growth plate is asked to carry more load than it is ready for.

Is Physitis Just From Overfeeding?

Not always, but overfeeding energy is one of the big risk factors.

Many foals with physitis are being pushed for fast growth, especially in sale or show preparation. Too many calories, especially from high-starch or high-sugar concentrates, can drive rapid or uneven growth. Rutgers Equine Science Center describes developmental orthopaedic disease as multifactorial, with genetics, nutrition, and exercise all playing a role, and notes that erratic growth rate may be more important than rapid growth alone. (esc.rutgers.edu)

This matters because the answer is not simply “feed less.”

The answer is:

• Reduce excessive calories

• Avoid rapid weight gain

• Balance minerals properly

• Support steady growth

• Avoid starving protein, vitamins, or trace minerals

• Monitor growth and body condition over time

A foal with physitis does not need to be put on a crash diet. It needs a corrected diet.

Protein: Should You Cut It?

This is where advice often gets messy.

Older-style advice often blamed high protein for growth problems. The evidence is more nuanced. Rutgers notes that excessive protein was historically suspected as a cause of developmental orthopaedic disease, but later studies did not show a direct relationship, and protein restriction in growing horses may reduce growth rate and impair bone mineralisation. (esc.rutgers.edu)

Merck’s professional guidance for physitis recommends decreasing food intake to reduce body weight or growth rate, correcting the diet, adjusting the calcium-to-phosphorus ratio, and limiting protein content in that context. (Merck Veterinary Manual)

So the safest clinical interpretation is:

Do not starve the foal of protein. Do not overfeed rich energy-dense diets either.

Work with your vet or equine nutritionist to reduce unnecessary calories while maintaining high-quality protein, calcium, phosphorus, copper, zinc, and other nutrients needed for normal bone development.

Calcium, Phosphorus and Trace Minerals Matter

Growth plates need proper mineral support.

Important nutrients include:

• Calcium

• Phosphorus

• Copper

• Zinc

• Balanced energy

• Adequate high-quality protein

• Vitamin and mineral balance

Rutgers notes that mineral imbalances are well documented contributors to developmental orthopaedic disease, including deficiencies of calcium, phosphorus, and copper. It also lists recommended mineral concentrations for rations fed to rapidly growing young horses. (esc.rutgers.edu)

Merck specifically advises correcting the calcium-to-phosphorus ratio in physitis cases. (Merck Veterinary Manual)

This is why guessing with supplements can backfire. Adding one mineral without checking the whole diet can create a different imbalance.

Is Alfalfa Bad for Physitis?

Not automatically.

The draft says to avoid rich alfalfa, but that is too simplistic. Alfalfa is higher in calcium and protein than many grass hays, and it can be useful in some young horse diets when used correctly. The issue is not alfalfa by itself. The issue is the total ration: calories, calcium, phosphorus, protein, trace minerals, forage quality, concentrates, pasture, growth rate, and body condition.

A foal on too much rich forage and concentrate may need calories reduced.

A foal on poor grass hay with mineral deficiencies may need a better-balanced ration, not less nutrition.

In practice, do not remove or add alfalfa blindly. Test the forage, calculate the ration, and adjust with your vet or nutritionist.

Exercise: Is Turnout Good or Bad?

Both over-exercise and over-restriction can be problems.

Foals need movement for healthy bone development, but a foal with active painful physitis may need exercise restricted temporarily. Merck recommends restricting exercise to a yard or large, well-ventilated loose box with a soft surface during treatment. (Merck Veterinary Manual)

Rutgers notes that forced exercise and excessive concussion can contribute to developmental orthopaedic disease, but also warns that overly restricting exercise can negatively affect bone growth and development. Turnout is generally beneficial for growing foals when they are sound and managed appropriately, while strenuous forced exercise, especially lunging in circles, should be avoided. (esc.rutgers.edu)

The practical rule:

Rest the painful growth plate, but do not raise young horses in a way that prevents normal controlled movement for months without a reason.

How Worried Should You Be?

Low Risk

This is more likely when:

• Swelling is mild

• The foal is not lame

• The foal is bright, eating, and moving comfortably

• The swelling is symmetrical

• There is no fever

• There is no limb deviation

• The foal is not rapidly gaining excess weight

Action: book a routine veterinary check, review diet and growth rate, monitor limb shape, and reduce unnecessary high-energy feed if advised.

Moderate Risk

This is more likely when:

• Growth plate swelling is obvious

• The area is warm or painful

• The foal is mildly lame

• The foal is heavy, fast-growing, or heavily muscled

• The foal is on high-concentrate feed

• The ground is hard and dry

• Swelling is worsening over days

Action: call your vet. The foal may need radiographs, diet correction, controlled exercise, pain relief, hoof trimming review, and follow-up.

High Risk

This is more likely when:

• Lameness is moderate or severe

• The foal is reluctant to move

• One limb is much worse than the others

• The limb is becoming crooked

• The foal has fever or depression

• There is marked pain

• Infection, trauma, fracture, or osteomyelitis is possible

• The foal is very young, weak, or systemically unwell

Action: this needs prompt veterinary assessment. Do not assume it is simple growth pain.

Critical

Treat this as urgent if:

• The foal is severely lame

• The foal will not bear weight normally

• The foal has fever

• The foal is dull, not nursing, or not eating

• There is rapid swelling

• A joint is swollen, hot, or painful

• There is a wound near a joint or growth plate

• The foal is under 2 months old and has limb swelling or lameness

• Septic physitis, septic arthritis, or fracture is possible

Action: call your vet immediately. Septic physitis and joint infection can permanently damage a foal’s limb if treatment is delayed.

When Is Physitis an Emergency?

Physitis becomes an emergency when the signs suggest infection, fracture, severe pain, or joint involvement.

Call your vet urgently if your foal has:

• Severe lameness

• Fever

• Depression

• Reduced nursing or appetite

• A hot swollen joint

• Rapidly worsening swelling

• A wound near the growth plate

• A limb that is becoming crooked

• Pain that is much worse on one side

• Signs in a very young foal

• Any suspicion of septic arthritis or septic physitis

Septic physitis is infection of the growth plate and is different from uncomplicated nutritional or mechanical physitis. Radiographic studies of septic physitis in foals describe focal bone destruction centred on the physis, and septic physitis may occur with septic arthritis or osteomyelitis. (ResearchGate)

The practical warning is simple: fever plus growth plate swelling is not normal physitis until proven otherwise.

What Else Can Look Like Physitis?

Growth plate swelling in a foal is not always simple physitis.

Important rule-outs include:

Septic Physitis

This is infection in the growth plate. It is much more serious than routine physitis and may need aggressive antibiotics, local treatment, surgery, or referral care. Septic physitis may be associated with bacteremia, failure of passive transfer, septic joints, or umbilical infection in young foals. (imaging.vetmed.ufl.edu)

Septic Arthritis

A hot, swollen, painful joint in a foal is an emergency. A foal with septic arthritis may deteriorate quickly and can suffer permanent joint damage.

Osteomyelitis

Bone infection can occur near the growth plate or joint. It may mimic physitis but requires a much more aggressive treatment plan.

Growth Plate Fracture

Trauma can injure the physis. Radiographs are needed when the foal is very lame, one limb is worse, or trauma is suspected.

Angular Limb Deformity

Physitis can occur alongside limb deviation, but angular limb deformity can also develop for other reasons and may need time-sensitive management.

Osteochondrosis

Physitis can occur with other developmental orthopaedic diseases such as osteochondrosis. Merck notes that physitis may occur along with osteochondrosis. (Merck Veterinary Manual)

Flexural Limb Deformity

Pain from physitis can make a foal unload a limb or alter posture, contributing to flexural problems. Merck notes acquired flexural deformities may develop in response to long-term pain, including pain from physitis. (Merck Veterinary Manual)

Trauma or Soft Tissue Injury

A kick, fall, or paddock accident can cause swelling near the joint or growth plate.

The key is this: do not diagnose physitis by appearance alone if the foal is lame, febrile, one-sided, or worsening.

How Do Vets Diagnose Physitis?

Your vet may diagnose uncomplicated physitis based on history, age, physical exam, swelling location, pain, body condition, growth rate, and diet history.

A veterinary workup may include:

• Full physical exam

• Temperature check

• Lameness assessment

• Palpation of growth plates

• Comparison between limbs

• Hoof and limb alignment assessment

• Body condition scoring

• Diet history

• Mare’s feed review if the foal is still nursing

• Forage and concentrate analysis

• Radiographs

• Bloodwork if infection is suspected

• Joint fluid testing if septic arthritis is possible

Radiographs are useful because they help confirm growth plate involvement and rule out fractures, infection, angular limb deformity, osteochondrosis, and other developmental orthopaedic problems. Merck states that radiography aids clinical assessment in physitis. (Merck Veterinary Manual)

Treatment for Physitis

Treatment depends on severity and cause.

The main goals are:

1. Reduce overload on the growth plate

2. Slow excessive or erratic growth safely

3. Correct diet imbalance

4. Control pain and inflammation

5. Protect limb alignment

6. Rule out infection or fracture

7. Monitor recovery

Merck summarises treatment as decreasing food intake to reduce body weight or growth rate, restricting exercise to a soft yard or loose box, ensuring frequent careful hoof trimming, and correcting diet imbalance. (Merck Veterinary Manual)

Diet Management

Diet changes should be targeted.

A good diet plan may include:

• Reducing high-energy concentrates

• Removing unnecessary sweet feed

• Avoiding sudden diet swings

• Using a properly formulated ration balancer where needed

• Maintaining adequate high-quality protein

• Correcting calcium and phosphorus balance

• Checking copper and zinc intake

• Testing forage

• Reviewing pasture quality

• Reviewing the mare’s diet if the foal is still nursing

• Monitoring body condition and growth rate

The aim is steady growth, not maximum growth.

A foal being prepared for sale or show does not benefit from being pushed until the growth plates complain. That is not premium development. That is biology sending an invoice.

Exercise and Rest

For active painful physitis, exercise should usually be restricted.

This may mean:

• Large, soft loose box

• Small yard turnout

• Short controlled movement

• Avoiding hard, dry ground

• Avoiding rough paddock play

• Avoiding forced exercise

• Avoiding lunging

• Separating from overly active companions if needed

Merck recommends restricting exercise to a yard or large, well-ventilated loose box with a soft surface such as peat moss, deep straw, shavings, or sand. (Merck Veterinary Manual)

Once pain and swelling settle, controlled turnout can usually be reintroduced gradually under veterinary guidance.

Pain Relief

Your vet may use NSAIDs in selected cases if the foal is painful.

Do not give medication without veterinary direction. Foals are not small adult horses, and dosing, hydration, age, kidney function, and concurrent disease matter.

Pain relief is useful when needed, but it should not be used to hide the problem while the foal continues to overload the growth plate.

Hoof Care

Hoof care matters more than many owners realise.

Poor foot balance can increase uneven loading across the limb and growth plate. Merck includes careful and frequent trimming as part of physitis treatment. (Merck Veterinary Manual)

Your vet and farrier may assess:

• Toe length

• Heel height

• Medial-to-lateral balance

• Limb alignment

• Uneven wear

• Whether the foal is loading one side more than the other

• Early angular limb deviation

This is especially important if one side of the growth plate is more affected and the limb is starting to deviate.

Should the Foal Be Weaned Early?

Sometimes, but not routinely.

Early weaning may be considered when:

• The foal is over-conditioned

• The mare is producing very rich milk

• The foal is being pushed by both milk and high-energy feed

• Diet control is impossible while the foal remains with the mare

• The foal is old enough and otherwise suitable for weaning

• The vet believes it will reduce growth plate overload

But early weaning is not automatically the answer. It can create stress, reduce movement patterns, and complicate nutrition if not handled properly.

The better question is: what is driving this foal’s growth rate and body condition?

How Long Does Physitis Take To Improve?

Mild cases may improve within a few weeks once diet and exercise are corrected.

More significant cases may take several weeks to a few months.

Recovery depends on:

• Severity of swelling

• Degree of lameness

• Whether infection is present

• Whether limb deviation is developing

• How quickly diet is corrected

• Body condition

• Ground conditions

• Exercise control

• Hoof balance

• Foal age and growth stage

The swelling may take time to fully remodel even after pain improves. The key is that heat, pain, and lameness should settle, and limb alignment should not worsen.

What Should You Do Right Now?

If you think your foal has physitis:

1. Stop Pushing Growth

Do not increase grain, rich feed, or sale-prep rations.

2. Call Your Vet

A vet should check the foal, especially if there is lameness, heat, pain, or swelling around a growth plate.

3. Take Photos

Take front, side, and rear limb photos every few days from the same angle. This helps track swelling and limb alignment.

4. Check Temperature

Fever makes infection more concerning.

5. Reduce Exercise if Painful

Keep the foal on soft footing and restrict rough play until assessed.

6. Review the Entire Diet

Include:

• Mare’s feed

• Foal creep feed

• Pasture

• Hay

• Supplements

• Grain

• Treats

• Mineral balancer

7. Do Not Starve the Foal

Cutting nutrition too aggressively can create new problems. Correct the ration, do not crash the growth curve.

8. Ask About Radiographs

Radiographs are especially useful if lameness is more than mild, swelling is one-sided, limb deviation is present, trauma is possible, or infection must be ruled out.

Common Mistakes Owners Make

Calling It “Growing Pains” and Waiting

Mild physitis may settle, but worsening swelling, heat, pain, or lameness needs veterinary attention.

Cutting Feed Too Aggressively

Foals still need nutrients to grow bone. The goal is balanced growth, not starvation.

Blaming Protein Alone

High energy and mineral imbalance are usually more important than protein alone. Protein restriction can be harmful if it deprives the foal of essential amino acids. (esc.rutgers.edu)

Ignoring the Mare’s Diet

If the foal is nursing and sharing the mare’s feed, the mare’s ration may be part of the problem.

Continuing Hard Turnout on Hard Ground

A sore growth plate on hard, dry ground is not a good combination. Merck notes physitis is common in fast-growing foals during summer when ground is dry and hard. (Merck Veterinary Manual)

Skipping Radiographs

Radiographs help rule out fracture, infection, angular limb deformity, and other developmental orthopaedic disease.

Forgetting the Farrier

Uneven hoof balance can worsen uneven loading across the growth plate.

Can Physitis Be Prevented?

Not every case is preventable, because genetics and conformation matter. But risk can be reduced.

Practical prevention includes:

• Aim for steady, moderate growth

• Avoid pushing foals for rapid size or sale condition

• Monitor body condition regularly

• Use feeds formulated for growing horses

• Avoid excessive sweet feed and high-starch concentrates

• Balance calcium and phosphorus

• Ensure copper and zinc are adequate

• Test forage where possible

• Review the mare’s diet while the foal is nursing

• Avoid forced exercise and lunging in young foals

• Provide safe turnout on suitable footing

• Avoid prolonged hard-ground concussion

• Keep hooves trimmed and balanced

• Monitor limbs closely during rapid growth periods

• Act early if swelling appears

AAEP describes foal nutrition as a balancing act because the nutritional start a foal receives can affect health and soundness for life. (AAEP)

The best prevention is not making the biggest foal fastest. It is producing the soundest horse long-term.

Case Example: Fast-Growing Foal With Fetlock Physitis

A 5-month-old warmblood colt develops firm swelling above both front fetlocks. He is bright and eating but takes short steps on hard ground. He is nursing well, eating the mare’s concentrate, and receiving extra creep feed because he is being prepared for inspection.

On exam, both distal cannon growth plates are enlarged, warm, and mildly painful. Radiographs support uncomplicated physitis and show no fracture or infection.

The plan includes:

• Reducing high-energy concentrate

• Moving to a balanced youngstock ration plan

• Reviewing the mare’s feed access

• Maintaining mineral balance

• Restricting turnout to a small soft paddock temporarily

• NSAIDs for comfort under veterinary direction

• Farrier review for hoof balance

• Recheck in 2 to 3 weeks

The important part is not simply “less feed.” The important part is controlled growth, balanced minerals, softer footing, and monitoring alignment.

Myth vs Reality

Myth	Reality
Physitis is just harmless growing pains.	It is growth plate inflammation and can affect comfort, alignment, and long-term soundness if ignored.
Only overfed foals get physitis.	Overfeeding is common, but conformation, hard ground, exercise, genetics, mineral imbalance, trauma, and infection can also contribute.
Cutting protein fixes it.	Protein alone is not the simple villain. Foals need adequate quality protein and balanced minerals for normal bone growth.
Alfalfa must always be removed.	Not always. The whole ration matters more than blaming one forage.
A symmetrical swelling is never serious.	Symmetry is often less alarming than one-sided severe swelling, but pain, heat, lameness, and progression still matter.
Radiographs are only needed for severe cases.	Radiographs are useful whenever lameness, deformity, infection, fracture, or uncertainty is present.

FAQs About Physitis in Foals

Is physitis painful?

It can be. Mild cases may cause swelling with little lameness, but active physitis can be warm, painful, and associated with stiffness or lameness. Severe pain should prompt urgent veterinary assessment. (Merck Veterinary Manual)

Can physitis go away on its own?

Mild cases may improve with growth and better management, but you should still review the foal’s diet, exercise, hoof balance, and body condition. Waiting while swelling worsens can risk limb deviation or delayed diagnosis of infection.

Should I reduce my foal’s feed?

Often the energy intake needs to be reduced, but the diet must stay balanced. Do not starve the foal or remove key nutrients. Work with your vet or nutritionist to reduce excessive calories while maintaining protein, calcium, phosphorus, copper, zinc, and vitamins.

When should I get radiographs?

Radiographs are recommended if the foal is lame, painful, one-sided, worsening, developing limb deviation, has a fever, had trauma, or if your vet needs to rule out fracture, infection, osteomyelitis, angular limb deformity, or other developmental orthopaedic disease.

Can physitis affect future soundness?

Most uncomplicated cases do well when caught early and managed properly. The risk increases when physitis is severe, ignored, associated with limb deviation, complicated by infection, or when rapid growth and overload continue.

The Bottom Line

Physitis is common in growing foals, but it should not be brushed off as simple growing pains.

It means the growth plate is inflamed. The foal may be growing too fast, carrying too much weight, working too hard on immature bone, standing on hard ground, loading the limb unevenly, or eating a ration that is not properly balanced.

The safest approach is:

• Recognise swelling early

• Call your vet if there is heat, pain, or lameness

• Use radiographs when the case is painful, one-sided, severe, or uncertain

• Reduce excessive calories without starving the foal

• Balance minerals properly

• Restrict exercise temporarily on soft footing

• Keep hoof care frequent and careful

• Monitor limb alignment closely

A foal does not need to win the growth race. The goal is a sound adult horse, not the biggest youngster in the paddock by six months old.

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If your foal has swollen growth plates, stiffness, rapid growth, limb deviation, or you are unsure whether the diet is supporting safe development, ASK A VET™ can help you organise photos, diet history, growth patterns, and the right questions to discuss with your veterinarian or equine nutritionist.