Tying Up in Horses: PSSM, RER and What To Do

By Dr Duncan Houston

“Tying up” is one of those horse terms that sounds simple until you realise it can mean several different muscle disorders. One horse may tie up after being pushed too hard while unfit. Another may have a recurrent genetic or inherited muscle condition. Another may look stiff and sore after only light work because the muscles store or use energy abnormally.

That difference matters because the treatment is not the same for every horse.

A Quarter Horse with PSSM does not need the same long-term plan as a nervous Thoroughbred with recurrent exertional rhabdomyolysis. A one-off tying-up episode after heat, dehydration and overwork is different again.

This article explains what tying up is, when it is an emergency, how vets diagnose PSSM and other forms of exertional rhabdomyolysis, and how diet, exercise and testing can help prevent future episodes.

Quick Answer

Tying up is a painful muscle disorder in horses, usually involving cramping, stiffness and muscle damage during or after exercise. Vets often call it exertional rhabdomyolysis. It may be a one-off sporadic episode caused by overwork, heat, dehydration or electrolyte problems, or it may be recurrent because of conditions such as PSSM, recurrent exertional rhabdomyolysis, malignant hyperthermia or other muscle diseases. If your horse becomes very stiff, sweats heavily, refuses to move, has dark urine or seems distressed, stop exercise and call your vet urgently. Merck Veterinary Manual advises stopping exercise immediately when signs of exertional rhabdomyolysis appear and moving the horse to a well-bedded stall with access to fresh water. (Merck Veterinary Manual)

What Does “Tying Up” Mean?

Tying up is the common name for painful muscle cramping and muscle fibre damage associated with exercise. The veterinary term is usually exertional rhabdomyolysis.

During an episode, muscle cells are damaged and leak enzymes such as creatine kinase, or CK, and aspartate aminotransferase, or AST, into the blood. In more severe cases, muscle pigment called myoglobin can enter the urine, making it look dark red, brown, tea-coloured or coffee-coloured. That is serious because myoglobin, dehydration and some medications can all increase the risk of kidney damage. Merck notes that severe rhabdomyolysis can compromise the kidneys because of myoglobinuria, dehydration and NSAID use, especially if fluid balance is not restored. (Merck Veterinary Manual)

In simple terms: the muscles are not just “a bit sore.” They can be actively breaking down.

What Are the Signs of Tying Up?

Signs can range from mild stiffness to a horse that refuses to move.

Common signs include:

• Stiffness during or after exercise

• Short, tight hind limb steps

• Firm, painful muscles over the back, loin, croup or hindquarters

• Sweating more than expected

• Muscle trembling or twitching

• Reluctance to move forward

• Pawing, anxiety or colic-like behaviour

• Increased heart rate or breathing rate

• Dark urine in severe cases

• Weakness or recumbency in severe cases

PSSM1 horses may show a tucked-up abdomen, camped-out stance, sweating, muscle fasciculations, hind limb stiffness, gait asymmetry and reluctance to move, and some may even paw or roll like a colic case. (Merck Veterinary Manual)

That is why a tying-up episode can be confusing. It may look like colic, lameness, heat stress, back pain or a horse simply refusing to work. The pattern and bloodwork matter.

The Three Main Owner-Friendly Categories

There are several causes of exertional muscle disease in horses, but for owners, tying up is easiest to understand in three broad groups.

Type	Common pattern	Breeds often involved	Main management focus
Sporadic tying up	One-off episode after overwork, heat, dehydration or illness	Any breed	Rest, fluids, correct trigger, gradual return to work
Recurrent exertional rhabdomyolysis	Repeated episodes, often in fit, nervous horses	Thoroughbreds, Standardbreds, Arabians	Routine, stress control, regular exercise, lower starch
PSSM	Muscle energy storage disorder, often recurrent or triggered by rest and light exercise	Quarter Horse-related breeds, drafts, Morgans, some Warmbloods	Low-NSC diet, daily exercise, turnout, genetic testing for PSSM1

Vets may also rule out malignant hyperthermia, myofibrillar myopathy, MYH1 myopathy, glycogen branching enzyme deficiency, vitamin E or selenium issues, and other neuromuscular diseases. UC Davis specifically notes that other causes of tying up besides PSSM include malignant hyperthermia, glycogen branching enzyme deficiency and myosin heavy chain myopathy, which need to be ruled out so the horse is treated correctly. (Centre for Equine Health)

Type 1: Sporadic Exertional Rhabdomyolysis

Sporadic tying up is usually a one-off or occasional event caused by a temporary trigger.

Common triggers include:

• Exercise beyond the horse’s fitness level

• Sudden hard work after time off

• Heat stress

• Dehydration

• Electrolyte imbalance

• Respiratory disease or recent viral illness

• Poor conditioning

• Diet imbalance

• Vitamin E, selenium or sodium deficiency in some cases

Merck states that all breeds can develop sporadic exertional rhabdomyolysis, and the most common cause is exercise that exceeds the horse’s state of training. It also notes that respiratory disease outbreaks and dietary deficiencies of sodium, vitamin E, selenium or calcium-phosphorus balance may contribute. (Merck Veterinary Manual)

The practical version: the horse’s muscles were asked to do more than they were prepared to do.

Most sporadic cases do not become a lifelong problem if the trigger is corrected. But severe episodes still need veterinary care because muscle breakdown can be dangerous.

Type 2: Recurrent Exertional Rhabdomyolysis

Recurrent exertional rhabdomyolysis, or RER, is a recurring tying-up disorder most often associated with Thoroughbreds, Standardbreds and Arabians.

RER is different from PSSM. It is not caused by the PSSM1 GYS1 mutation. It is thought to involve abnormal regulation of calcium inside muscle cells, with episodes often triggered by stress, excitement, fitness, high-starch diets and inconsistent routines. Merck describes RER as frequent in Thoroughbreds, Standardbreds and Arabian horses in high-stress environments, and notes that fit, nervous horses fed high nonstructural carbohydrate diets are particularly susceptible. (Merck Veterinary Manual)

Signs often appear during or shortly after exercise and may be more likely when the horse is tense, held back, stressed or coming off a rest day.

Management usually focuses on:

• Consistent daily routine

• Reducing stress and excitement

• Regular controlled exercise

• Avoiding prolonged stall rest

• Reducing starch and sugar

• Using fat as a safer calorie source when needed

• Managing turnout and training schedule carefully

The mistake is treating these horses as if they simply need more rest. Chronic tying-up horses often do worse with long breaks and then sudden reintroduction to work.

Type 3: PSSM

PSSM stands for polysaccharide storage myopathy. It is a muscle disorder involving abnormal glycogen storage in muscle cells. Glycogen is the stored form of sugar used by muscle for energy.

University of Minnesota describes PSSM as a disorder that causes horses to store too much or abnormal glycogen in muscle, leading to painful cramping or tying up. It notes that Quarter Horses and related breeds often show tying up, draft horses may show muscle breakdown and progressive weakness, and Warmbloods may show muscle soreness and gait abnormalities. (University of Minnesota Extension)

PSSM is not one simple condition. The two main categories are PSSM1 and PSSM2.

PSSM1: The Genetic Form Most Owners Know

PSSM1 is caused by a mutation in the GYS1 gene, which affects glycogen synthesis. It is autosomal dominant, meaning one copy of the mutation can be enough for a horse to be affected. UC Davis notes that PSSM1 can be diagnosed using a genetic test on hair or blood samples, and that it is a glycogen storage disease causing abnormal accumulation of complex sugars in muscle cells. (Veterinary Genetics Laboratory)

PSSM1 is commonly seen in:

• Quarter Horses

• Paints

• Appaloosas

• Draft breeds

• Morgans

• Some Warmbloods

• Several other breeds

UC Davis lists Quarter Horses and related breeds, draft breeds and multiple other breeds as appropriate for PSSM1 testing. (Veterinary Genetics Laboratory)

A classic PSSM1 pattern is a heavily muscled horse that becomes stiff, sore or tied up after light work, especially after a few days of rest.

That last part is important. Many PSSM horses do worse after days off. The owner thinks they are being kind by resting the horse. The horse’s muscles quietly disagree.

PSSM2: Be Careful With the Label

PSSM2 is more complicated.

Historically, PSSM2 has referred to horses with PSSM-like signs and abnormal glycogen storage on muscle biopsy, but without the PSSM1 GYS1 mutation. UC Davis states that PSSM2 may be genetic, but the exact cause is unknown, and there are currently no scientifically verified DNA tests for PSSM2. It also notes that muscle biopsy can be used to evaluate muscle damage and glycogen storage. (Centre for Equine Health)

This is where the article needs to be very clear.

Commercial “PSSM2 genetic panels” are widely discussed online, but they are controversial. A peer-reviewed Equine Veterinary Journal study found no significant association between several commercial PSSM2 or myofibrillar myopathy variants and histopathological diagnosis, and the authors concluded they could not recommend those variant genotypes for diagnosis, prepurchase selection, breeding decisions or myopathy diagnosis. (PubMed)

So the safest advice is:

• PSSM1 genetic testing is valid and useful.

• PSSM2 is not currently diagnosed by a universally accepted, validated DNA test.

• A negative PSSM1 test does not mean the horse has no muscle disease.

• A commercial PSSM2 panel result should be interpreted cautiously with your vet.

• Muscle biopsy and specialist input may be needed in difficult cases.

This is one of those areas where internet groups can become very confident very quickly. Confidence is lovely. Validation is better.

How Worried Should You Be?

Mild

Mild tying up may look like stiffness, short steps, mild muscle soreness or reluctance to go forward, but the horse is bright, drinking, passing normal urine and not distressed.

What to do: stop exercise, keep the horse calm, offer water and call your vet for advice. Do not continue riding to “work it out.”

Moderate

Moderate tying up may involve obvious stiffness, sweating, painful muscles, trembling, increased breathing, reluctance to move or repeated episodes.

What to do: stop exercise and arrange a veterinary exam. Bloodwork for CK and AST is usually needed.

Severe

Severe tying up may involve refusal to move, dark urine, severe sweating, marked pain, weakness, depression or signs that look like colic.

What to do: call a vet urgently. Severe muscle breakdown can damage the kidneys, especially if the horse is dehydrated or given NSAIDs without fluid assessment. (Merck Veterinary Manual)

Recurrent or High Risk

Recurrent episodes, tying up after light exercise, episodes after rest days, repeated high CK values, or affected Quarter Horse-related breeds should raise concern for PSSM, RER or another muscle disorder.

What to do: do not just treat each episode as random soreness. This horse needs a diagnostic plan.

When Is This an Emergency?

Call your vet urgently if your horse has:

• Dark red, brown, tea-coloured or coffee-coloured urine

• Refusal to move

• Severe muscle pain

• Heavy sweating at rest

• Rapid breathing or high heart rate

• Weakness or collapse

• Recumbency

• Signs of dehydration

• Signs of colic

• Fever or heat stress

• Stiffness that worsens over minutes to hours

• A first-ever severe tying-up episode

• A known PSSM or RER horse having a major episode

Do not force the horse to keep walking if they are severely stiff or painful. Movement can worsen muscle damage during an active episode.

Merck advises stopping exercise immediately, moving the horse to a well-bedded stall with water, relieving pain and anxiety, and correcting fluid and acid-base deficits. NSAIDs may be used in a well-hydrated horse, but severe cases with myoglobinuria need fluid support and kidney monitoring. (Merck Veterinary Manual)

In plain English: do not bute-and-boot the horse down the road. This is not a “walk it off” problem.

What Else Can Look Like Tying Up?

Not every stiff or reluctant horse is tying up.

Important rule-outs include:

• Colic

• Laminitis

• Heat stress or exhaustion

• Dehydration

• Electrolyte imbalance

• Back pain

• Sacroiliac pain

• Hock or stifle lameness

• Neurological disease

• Stringhalt

• Shivers

• HYPP

• Malignant hyperthermia

• MYH1 myopathy

• Myofibrillar myopathy

• Tetanus

• Azoturia-like muscle disease from other causes

• Recent viral illness or systemic disease

This is why bloodwork matters. A horse that looks “tied up” may have high CK and AST, or they may have an entirely different problem.

How Vets Diagnose Tying Up

Diagnosis starts with the episode itself, then moves into why it happened.

Your vet may assess:

• History and exercise pattern

• Whether this is the first episode or recurrent

• Breed and family history

• Recent rest days

• Diet, grain, pasture and hay

• Fitness level

• Weather and hydration

• Stress or transport

• Muscle pain and firmness

• Urine colour

• Temperature, heart rate and respiratory rate

• Hydration status

Blood Tests

The most important early tests are usually CK and AST.

CK rises quickly after muscle damage and can help confirm an active episode. AST rises and falls more slowly, so it can help assess ongoing or more prolonged muscle injury.

Merck notes that sporadic exertional rhabdomyolysis is diagnosed using clinical signs of muscle cramping and stiffness after exercise with moderate to marked increases in CK and AST. It also notes that chronic tying-up diagnosis may include CBC, serum biochemistry, vitamin E and selenium levels, dietary analysis, exercise testing, genetic testing and muscle biopsy. (Merck Veterinary Manual)

Urine Testing

If the urine is dark, your vet may check for myoglobin and kidney risk. Severe rhabdomyolysis can cause myoglobinuria, and kidney monitoring may be needed in serious cases. (Merck Veterinary Manual)

Genetic Testing

PSSM1 can be diagnosed using a hair or blood test for the GYS1 mutation. UC Davis notes that hair root samples are suitable for their PSSM1 genetic test. (Veterinary Genetics Laboratory)

Depending on breed and signs, your vet may also discuss testing for other genetic diseases such as malignant hyperthermia or MYH1 myopathy.

Muscle Biopsy

Muscle biopsy may be used when genetic testing does not explain the horse’s signs or when PSSM2, myofibrillar myopathy, RER or other muscle disease is being investigated.

Merck states that PSSM2 diagnosis is based on absence of the GYS1 mutation plus abnormal glycogen patterns in muscle biopsy, while myofibrillar myopathy is diagnosed by identifying desmin aggregates in muscle biopsy samples. (Merck Veterinary Manual)

Exercise Challenge Testing

In selected cases, vets may measure CK before and after controlled light exercise. Merck notes that exercise challenge testing can detect subclinical cases by measuring CK before and 4 hours after light exercise. (Merck Veterinary Manual)

This should only be done under veterinary direction. Do not “test” a tying-up horse at home by working them hard to see what happens. That is how muscles file a formal complaint.

What To Do During an Acute Episode

If your horse starts tying up:

1. Stop exercise immediately.

2. Keep the horse calm.

3. Do not force continued walking if the horse is very stiff or painful.

4. Move the horse only as much as is safely necessary.

5. Put the horse in a well-bedded stall or quiet safe area.

6. Offer fresh water.

7. Do not give grain or sweet feed.

8. Do not give NSAIDs unless your vet advises it, especially if the horse may be dehydrated.

9. Check urine colour if the horse urinates.

10. Call your vet, especially if signs are severe, recurrent or not improving.

Most mild to moderate horses become more comfortable within 18 to 24 hours once managed properly, but severe cases need more intensive treatment, fluids and monitoring. (Merck Veterinary Manual)

Long-Term Management for PSSM

PSSM management is built around diet and daily movement.

Diet

The aim is to reduce sugar and starch intake, avoid large insulin spikes and provide energy from safer sources.

Common principles include:

• Forage-first feeding

• Low-NSC hay

• Avoiding grain and sweet feed

• Using a ration balancer for vitamins and minerals

• Adding fat only if extra calories are needed

• Monitoring body condition carefully

• Avoiding obesity

• Testing hay where possible

University of Minnesota recommends hay with less than 10% nonstructural carbohydrates and avoiding grains, sweet feeds and other high-sugar feedstuffs in PSSM horses. (University of Minnesota Extension)

UC Davis recommends limiting dietary nonstructural carbohydrates to less than 12% of the diet, using low-NSC grass hay and a quality ration balancer for many easy keepers, with low-NSC or high-fat feed added only if extra calories are needed. (Centre for Equine Health)

The important point is not “add fat to every PSSM horse.” Many PSSM horses are easy keepers. Calories still count. A low-starch fat supplement can help some horses, but it can also make others obese if used carelessly.

Exercise

Daily exercise and turnout are just as important as diet.

University of Minnesota states that regular exercise without long periods of inactivity is key, and that mild to moderate PSSM horses can return to normal performance with proper management. (University of Minnesota Extension)

UC Davis notes that PSSM horses must exercise daily to maximise the muscles’ ability to burn glycogen, and that 90% of PSSM1 horses whose owners adhere to diet and exercise management have few to no tying-up episodes. Signs are likely to return if the management program is disrupted. (Centre for Equine Health)

That is the big owner message: PSSM management works best when it is boring, daily and consistent.

PSSM horses do not love random days off followed by “let’s see how fresh he feels today.” Spoiler: the muscles will have opinions.

Long-Term Management for RER

RER management is different from PSSM, although there can be overlap in diet.

The focus is usually:

• Reduce stress

• Keep a predictable routine

• Avoid high-starch feeds

• Provide regular daily exercise

• Avoid long periods of stall rest

• Avoid excitement before work

• Keep training consistent

• Manage turnout carefully

• Use fat calories if extra energy is needed

• Discuss medication only for difficult cases

Merck describes RER as triggered by stress in susceptible horses, with fit, nervous horses on high nonstructural carbohydrate diets being most at risk. (Merck Veterinary Manual)

For RER, the horse’s brain and routine matter as much as the feed bin. Some of these horses do not just need a diet sheet. They need a lifestyle sheet.

What About Vitamin E, Selenium and Electrolytes?

These can matter, but they should not be guessed.

Vitamin E and selenium deficiencies may contribute to muscle disease in some horses, and electrolyte problems can contribute to sporadic tying up, especially during hot weather or endurance work. Merck lists vitamin E, selenium, sodium and calcium-phosphorus imbalance as possible contributors in sporadic exertional rhabdomyolysis. (Merck Veterinary Manual)

But selenium can be toxic if over-supplemented.

The safest plan is:

• Test vitamin E if deficiency is suspected.

• Assess selenium based on region, diet and bloodwork where appropriate.

• Use electrolytes strategically in sweating horses.

• Make sure salt and water intake are adequate.

• Do not dump multiple supplements in at once and hope.

Supplements should fill a measured gap, not become nutritional confetti.

What Should You Feed a Horse With PSSM?

A practical PSSM feeding framework:

1. Base the diet on low-NSC forage.

2. Test hay if possible.

3. Avoid oats, corn, sweet feed and high-starch concentrates.

4. Use a ration balancer to meet protein, vitamin and mineral needs.

5. Add fat only if extra calories are needed.

6. Keep body condition controlled.

7. Restrict pasture if it triggers signs or weight gain.

8. Provide salt and clean water.

9. Make changes gradually.

10. Work with your vet or equine nutritionist.

For PSSM1, Merck describes an ideal diet as forage at 1.5% to 2% of body weight, more than 15% of digestible energy as fat and starch limited to less than 10% of daily digestible energy, while also warning that calorie needs must be assessed first to avoid obesity. (Merck Veterinary Manual)

So yes, low-starch matters. But no, the answer is not making every PSSM horse fat on oil and rice bran.

What Should You Do After the First Episode?

After the horse is comfortable and your vet has assessed the episode:

1. Check CK and AST.

2. Recheck enzymes until they are trending down or normal.

3. Review the horse’s training schedule.

4. Review recent rest days and workload changes.

5. Review diet, grain, pasture and forage.

6. Check hydration and electrolyte strategy.

7. Consider vitamin E and selenium testing if relevant.

8. Consider PSSM1 testing in at-risk breeds.

9. If recurrent, discuss RER, PSSM2, MFM, MH and other muscle disease testing.

10. Return to work gradually under veterinary guidance.

Merck notes that sporadic cases usually respond to rest, gradual increase in training and dietary adjustment once the temporary trigger has been addressed. (Merck Veterinary Manual)

Do not just wait until the horse looks better and then return to the same management. That is how episode two gets booked.

Common Mistakes Owners Make

Walking the Horse Too Much During an Active Episode

A mildly stiff horse may need careful handling, but a severely painful horse should not be forced to keep walking. Stop exercise and call your vet.

Giving NSAIDs Without Thinking About Hydration

NSAIDs can be appropriate in a well-hydrated horse under veterinary direction, but severe rhabdomyolysis with dehydration and myoglobinuria increases kidney risk. (Merck Veterinary Manual)

Treating Every Case the Same

Sporadic tying up, RER and PSSM are different problems. The long-term plan should match the diagnosis.

Resting PSSM Horses for Long Periods

Many PSSM horses need daily turnout and regular exercise. Long rest periods can trigger signs when work restarts.

Ignoring Forage Sugar

Owners often remove grain but forget that high-NSC hay or pasture can still trigger problems in PSSM horses.

Trusting Unvalidated PSSM2 Panels Too Strongly

PSSM1 testing is solid. PSSM2 commercial genetic testing is much more controversial, and current evidence does not support using some commercial variants as a stand-alone diagnosis. (PubMed)

Not Testing After a First Episode in an At-Risk Breed

A Quarter Horse, Paint, Appaloosa, draft horse or Morgan with tying-up signs should raise PSSM1 on the list.

Breeding Without Knowing PSSM1 Status

PSSM1 is autosomal dominant, so affected horses can pass the mutation to offspring. UC Davis notes that horses with one copy may transmit the variant to 50% of offspring, while horses with two copies transmit it to all offspring. (Veterinary Genetics Laboratory)

Can Tying Up Be Prevented?

Not every case can be prevented, but many episodes can be reduced.

Practical prevention includes:

• Build fitness gradually.

• Avoid sudden hard work after time off.

• Keep exercise consistent.

• Reduce grain on rest days if appropriate.

• Avoid high-starch feeds in susceptible horses.

• Use low-NSC forage for PSSM horses.

• Provide daily turnout.

• Keep RER horses on predictable routines.

• Manage stress and excitement.

• Ensure clean water and salt are always available.

• Use electrolytes appropriately in sweating horses.

• Avoid working sick horses.

• Avoid hard work in heat and humidity without conditioning.

• Test at-risk breeds for PSSM1.

• Investigate recurrent episodes properly.

For PSSM horses, prevention is usually daily management. For RER horses, prevention is routine and stress control. For sporadic tying up, prevention is conditioning, hydration and not asking the horse to go from couch potato to Olympic eventer by Thursday.

Will My Horse Be Okay?

Many horses recover well from tying up, especially if the episode is mild, treated early and the underlying cause is identified.

The outlook is better when:

• The horse is treated early.

• Urine remains normal colour.

• CK and AST fall appropriately.

• The horse stays hydrated.

• Kidney values remain normal.

• The episode was sporadic.

• Diet and exercise triggers are corrected.

• PSSM or RER is diagnosed and managed properly.

The outlook is more guarded when:

• The horse has dark urine.

• The horse is severely dehydrated.

• The horse refuses to move.

• CK is very high or stays high.

• Kidney values worsen.

• Episodes recur despite management.

• The horse has PSSM2, MFM, MH or another complex muscle disorder.

• The owner cannot maintain the required diet and exercise plan.

UC Davis notes there is no cure for PSSM, but most affected horses can be managed successfully, and many achieve acceptable performance levels. However, some cases are difficult to manage, and signs may return if the program is disrupted. (Centre for Equine Health)

That is the honest answer: tying up can be manageable, but it needs a diagnosis and consistency.

FAQs

Is tying up the same as PSSM?

No. PSSM is one cause of tying up, but tying up can also be sporadic, stress-related, diet-related, caused by RER, or linked to other muscle diseases. Diagnosis matters because the management is different.

How do I know if my Quarter Horse has PSSM?

PSSM1 can be diagnosed with a genetic test using hair or blood. Quarter Horses and related breeds are among the main breeds where PSSM1 testing is appropriate. (Veterinary Genetics Laboratory)

Should I walk a horse that is tying up?

Do not keep exercising the horse. If signs are mild, move the horse only as needed to a safe quiet area. If the horse is very stiff, painful or unwilling to move, do not force walking. Call your vet.

Can PSSM horses still work?

Yes, many can. With correct low-NSC diet, daily turnout and regular controlled exercise, many mild to moderate PSSM horses return to useful work. UC Davis reports that 90% of PSSM1 horses whose owners adhere to diet and exercise management have few to no episodes. (Centre for Equine Health)

Is there a genetic test for PSSM2?

There is no widely accepted, scientifically validated diagnostic DNA test for PSSM2 or MFM at this time. UC Davis states that PSSM2 diagnosis may involve muscle biopsy, and peer-reviewed research has found some commercial PSSM2 variants do not correspond to histopathological diagnosis. (Centre for Equine Health)

Final Thoughts

Tying up is not one disease. It is a syndrome with several possible causes, and the right plan depends on which type your horse has.

A one-off sporadic episode may be solved by rest, hydration, correcting diet and rebuilding fitness slowly. A recurrent Thoroughbred with stress-triggered episodes may need an RER plan built around routine and lower starch. A Quarter Horse, Paint, Appaloosa, draft or Morgan with stiffness after light work may need PSSM1 testing and a strict low-NSC, daily exercise program. A horse that tests negative for PSSM1 but keeps showing signs may need a deeper muscle disease work-up, not an internet diagnosis.

The main takeaway is simple: stop the horse during an episode, protect the kidneys, get the right tests, and build the prevention plan around the actual cause.

A horse that ties up is not being naughty. The muscles are telling you something. The trick is working out exactly what they are saying before the next ride.

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If your horse has tied up, has dark urine, keeps getting stiff after work, or you are unsure whether PSSM, RER or another muscle disease is involved, ASK A VET™ can help you understand what signs to monitor and what questions to ask your treating vet before the next step.