Shivers in Horses: Signs, Diagnosis and Management

Shivers is not cold trembling or bad behaviour. It is a progressive neurologic movement disorder that most often shows up when a horse backs up or has a hind foot lifted.

By Dr Duncan Houston

A horse with shivers can look completely normal walking, trotting, cantering, and working forward. Then the farrier picks up a hind leg, or the handler asks the horse to back up, and suddenly the limb trembles, lifts too high, swings away from the body, locks behind the horse, or slams back to the ground.

That is why shivers is so often mistaken for resistance, anxiety, training problems, pain during farrier work, or “being difficult.”

The reality is more complicated. Shivers is a neurologic movement disorder involving abnormal hindlimb control. There is no simple blood test, no quick cure, and no single supplement that fixes it. But many horses, especially mildly affected horses, can still live comfortable and useful lives with the right diagnosis, handling, farrier planning, exercise routine, and trigger management.

The key is recognising the pattern early and ruling out other conditions that can look similar.

Quick Answer

Shivers in horses is a progressive neurologic movement disorder classically recognised by abnormal hindlimb movement when backing up or when a hind foot is lifted. Affected horses may hyperflex the hind limb, hold it away from the body, tremble, hyperextend the limb behind them, or struggle with farrier work. There is no specific diagnostic test or cure, so diagnosis is based on clinical signs, especially signs while backing, and ruling out problems such as stringhalt, PSSM, HYPP, EPM, lameness, pain, and other neurologic disorders. Mild horses may continue work for years, while severe cases can become unsafe or difficult to manage. (Center for Equine Health)

What Is Shivers in Horses?

Shivers is a chronic, progressive neurologic movement disorder most commonly affecting the hind limbs. It is best recognised when the horse is asked to back up or when a hind limb is lifted for picking out the foot, trimming, or shoeing. (Center for Equine Health)

The classic signs include:

• Hindlimb trembling

• Sudden lifting of the hind leg

• Hindlimb hyperflexion

• Hindlimb hyperextension

• Abduction, where the limb moves away from the body

• Difficulty holding the hind foot up

• Trouble backing

• Tail elevation or trembling during an episode

• Farrier difficulty, especially with hind feet

At first, many horses move normally going forward. UC Davis notes that clinical signs are often absent at the trot and may only appear in the first few steps forward in more severe cases, especially after the horse has been standing or when turning sharply. (Center for Equine Health)

That forward-normal, backward-abnormal pattern is one of the biggest clues.

What Happens During a Shivers Episode?

During a shivers episode, the horse loses smooth control of one or both hind limbs during certain movements.

You may see:

• The hind leg suddenly snatched upward

• The limb held flexed and away from the body

• Muscle trembling through the thigh or hindquarter

• The tail lifting or trembling

• The foot held in the air longer than expected

• The leg placed down abruptly

• The horse struggling to back up

• The horse becoming anxious because the movement feels difficult

• The horse refusing to hold the hind foot for the farrier

Some horses show hyperflexion, where the hind limb lifts excessively. Others show hyperextension, where the hind limb is placed too far behind the body. Most affected horses have both hind limbs involved to some degree, although one side may look worse. UC Davis notes that forelimb signs are rare, but facial and neck muscle spasms may occur in some cases. (Center for Equine Health)

The horse is not choosing to be awkward. The movement pattern is abnormal because the nervous system is not coordinating the limb normally.

What Causes Shivers?

The exact cause is still not fully understood, but current research supports shivers as a neurologic disorder involving the cerebellum, the part of the brain important for coordination and movement control.

UC Davis describes shivers as being caused by damage to Purkinje cells in a specific area of the cerebellum, although the underlying mechanism remains unknown. (Center for Equine Health)

A 2015 study led by Valberg and colleagues found that horses with shivers had selective degeneration of Purkinje cell axons in the deep cerebellar nuclei. The authors concluded that shivers is characterised by end-terminal neuroaxonal degeneration that results in context-specific hypermetria and myoclonus. In plain English, the damage affects movement coordination during specific tasks, especially backing and hindlimb lifting. (PubMed)

That is a major reason shivers is now considered a neurologic movement disorder, not simply a muscle cramp or farrier behaviour issue.

Is Shivers the Same as PSSM?

No. Shivers and PSSM are different conditions, although they can occasionally occur in the same horse.

PSSM, or polysaccharide storage myopathy, is a muscle metabolism disorder. Shivers is a neurologic movement disorder. A study in Belgian Draft Horses found that PSSM and shivers were common but largely unrelated disorders, with only a small overlap between horses affected by both. (Experts@Minnesota)

This distinction matters because management advice can get muddled.

A low-starch, higher-fat diet is often discussed for PSSM and other muscle metabolism disorders. It may be useful if a horse truly has concurrent PSSM. But it should not be presented as a proven cure for shivers itself.

If a horse has signs of shivers and also has tying-up episodes, muscle pain, high CK, exercise intolerance, or breed risk for PSSM, your vet may investigate both.

Which Horses Are Most at Risk?

Shivers has been reported in multiple breeds, including draft horses, Warmbloods, Quarter Horses, and Thoroughbreds. UC Davis notes that geldings appear more likely to be diagnosed than mares and that taller horses, especially those over 16.3 hands, are at higher risk. (Center for Equine Health)

A later review reported that most horses with shivers show signs before 10 years of age, that geldings were diagnosed more often than mares, that ponies are rarely affected, and that tall horses are more susceptible. (The Horse)

Higher-risk groups include:

• Draft horses

• Warmbloods

• Tall geldings

• Quarter Horses

• Thoroughbreds

• Large sport horses

• Horses with early farrier difficulty involving the hind limbs

This does not mean every tall Warmblood with hind foot issues has shivers. It means the condition should be considered when the movement pattern fits.

Signs of Shivers in Horses

Early shivers can be subtle. Many horses are first noticed during farrier work rather than under saddle.

Common signs include:

• Trouble backing up

• Hindlimb trembling when backing

• Hindlimb hyperflexion

• Hindlimb hyperextension

• Snatching the hind foot away when lifted

• Difficulty holding a hind limb for trimming or shoeing

• Sudden stamping or slamming the hind foot down

• Tail elevation or trembling during an episode

• Stress-related worsening

• Signs triggered by excitement, backing, or lifting the foot

• Normal forward walk, trot, or canter in early stages

• Hindquarter weakness or muscle loss as the disease progresses

UC Davis notes that stress and excitement can trigger episodes and that muscle atrophy, especially of the thigh muscles, may occur as the disease progresses. (Center for Equine Health)

The most important diagnostic clue is this:

A true shivers horse usually shows signs when backing up.

UC Davis specifically warns that some horses hyperflex a hind limb when the foot is lifted but back up normally. Those horses do not meet the classic definition of shivers and may instead have an orthopaedic or pain-related issue. (Center for Equine Health)

Is Shivers Painful?

Shivers is primarily a movement control disorder, not a classic pain condition. However, affected horses may become stressed, fatigued, sore, or unsafe because they cannot control the hind limbs normally during certain tasks.

Pain may also exist alongside shivers.

A horse may have shivers and also have:

• Hock pain

• Stifle pain

• Suspensory pain

• Hoof pain

• Back pain

• Sacroiliac pain

• PSSM or another muscle disorder

• Farrier-related anxiety from repeated difficult experiences

That is why the diagnosis should not stop at “it looks like shivers.” A horse can have a neurologic movement disorder and still need a lameness or pain workup.

How Worried Should You Be?

Low Concern

This is more likely when:

• Signs are mild

• The horse backs with only slight hesitation

• The horse can still hold the hind feet briefly

• The horse is sound going forward

• There is no weakness, falling, or dangerous behaviour

• The farrier can work safely with small adjustments

• The signs are stable over time

Action: book a veterinary assessment, document videos, adjust farrier handling, keep the horse in consistent work, and monitor progression.

Moderate Concern

This is more likely when:

• The horse regularly struggles to back up

• The hind limb snatches or trembles when lifted

• Farrier work is becoming difficult

• One hind limb is much worse than the other

• Stress or excitement clearly worsens episodes

• The horse is developing thigh muscle loss or hindquarter weakness

• The horse is becoming anxious during handling

Action: arrange a veterinary neurologic and lameness exam. Build a farrier safety plan and review management, turnout, exercise, and triggers.

High Concern

This is more likely when:

• The horse cannot safely hold a hind limb

• The horse slams the limb down unpredictably

• Farrier work is unsafe

• Signs occur during forward movement

• The horse is becoming weak behind

• The horse stumbles, struggles to turn, or has worsening hindquarter control

• The horse’s work or quality of life is declining

Action: stop risky handling and ridden work until your vet has reassessed the horse. Sedation, stocks, modified farrier technique, diagnostic testing, or retirement from certain activities may be needed.

Critical

Treat the situation as urgent if:

• The horse falls

• The horse becomes recumbent

• The horse cannot rise

• The horse is weak, ataxic, or unsafe to move

• Breathing is abnormal

• The horse has sudden severe lameness

• There are signs of colic, collapse, seizure, or systemic illness

• The horse has a new acute neurologic change

Action: call your vet immediately. This is no longer a routine shivers management issue.

When Is Shivers an Emergency?

Shivers itself is usually a chronic management condition rather than a same-hour emergency. But signs that look like shivers can overlap with emergencies.

Call your vet urgently if your horse has:

• Sudden collapse

• Recumbency

• Inability to rise

• Severe weakness

• Ataxia or marked incoordination

• Sudden severe lameness

• Difficulty breathing

• Repeated falling

• Fever, depression, or severe systemic illness

• Acute trauma

• A limb that cannot bear weight

• Severe muscle pain or sweating suggestive of tying-up

• A suspected HYPP episode in a Quarter Horse related breed

HYPP is especially important because it can cause muscle tremors, weakness, paralysis, collapse, loud breathing, and sudden death during severe episodes. It can be confused with other conditions, and DNA testing is available. (Center for Equine Health)

If the horse is suddenly weak, collapsing, or breathing abnormally, do not assume it is “just shivers.”

How Do Vets Diagnose Shivers?

There is no single blood test, scan, or genetic test that confirms shivers in a living horse.

Diagnosis is based on:

• Clinical signs

• Observation while backing

• Observation while lifting hind limbs

• Neurologic examination

• Lameness examination

• Farrier history

• Video review

• Ruling out similar disorders

• Additional testing when needed

UC Davis states that there is no specific diagnostic test for shivers and that diagnosis is based on clinical signs and ruling out other potential causes such as stringhalt, EPM, and other disorders through lameness and neurologic examinations with additional diagnostic testing where needed. (Center for Equine Health)

A useful veterinary exam may include:

• Watching the horse walk forward

• Watching the horse back up

• Picking up each hind foot

• Assessing tail carriage and muscle tremors

• Neurologic tests such as backing, tight circles, tail pull, and limb placement

• Lameness exam

• Hoof, hock, stifle, suspensory, back, and pelvis assessment

• Bloodwork if muscle disease is suspected

• PSSM1 genetic testing where relevant

• HYPP testing in at-risk breeds

• Vitamin E and selenium assessment in selected cases

• Imaging if pain or lameness is suspected

Videos are extremely helpful because shivers signs can be intermittent. Record the horse backing, lifting each hind foot, and being handled for farrier-type positions if safe.

What Else Can Look Like Shivers?

This is where good veterinary reasoning matters.

A horse that trembles, snatches a hind leg, resists backing, or struggles with farrier work does not automatically have shivers.

Important rule-outs include:

Stringhalt

Stringhalt causes exaggerated flexion of one or both hind limbs, often while moving forward. It can be confused with shivers, especially when the hind limb lifts sharply.

The difference is that shivers is classically triggered by backing or lifting the hind limb, while stringhalt is often more visible during forward movement.

PSSM

PSSM is a muscle metabolism disorder. It can cause stiffness, tying-up, poor performance, muscle pain, and exercise intolerance. It is not the same as shivers, although both can occur in draft and Warmblood-type horses.

HYPP

HYPP can cause episodic muscle twitching, trembling, weakness, collapse, and loud breathing in Quarter Horses and related breeds. It is caused by a genetic sodium channel mutation, and only one copy of the mutation is needed for a horse to be affected. (University of Minnesota Extension)

Tying-Up or Rhabdomyolysis

Tying-up usually causes painful, firm muscles, sweating, reluctance to move, and elevated muscle enzymes. HYPP horses often appear normal after an episode, while tying-up horses usually remain painful for longer. (Center for Equine Health)

EPM

Equine protozoal myeloencephalitis can cause weakness, ataxia, muscle atrophy, asymmetric neurologic signs, and poor coordination. It needs a different diagnostic and treatment approach.

Cervical Vertebral Compressive Myelopathy

Also called wobblers, this can cause ataxia, weakness, toe dragging, stumbling, and poor proprioception. A wobbly horse should not be treated as a simple shivers case.

Hindlimb Pain

Hock arthritis, stifle pain, suspensory injury, hoof pain, sacroiliac pain, and back pain can all make a horse resist lifting a hind leg. UC Davis notes that horses that only hyperflex when the hind foot is picked up but back up normally likely have an underlying orthopaedic issue rather than shivers. (Center for Equine Health)

Farrier Fear or Learned Behaviour

A horse that has repeatedly lost balance, felt pain, or been punished during hind foot handling may become anxious or resistant. That can coexist with shivers or mimic it.

The key diagnostic question is:

Does the horse show the characteristic abnormal movement when backing up?

If yes, shivers becomes more likely. If no, keep looking.

Is There a Cure for Shivers?

No. There is currently no known cure or specific treatment that reverses shivers.

UC Davis states that there is currently no treatment for shivers, but consistent fitness, turnout, less time stalled, trigger reduction, and stress reduction may reduce episodes. (Center for Equine Health)

This can be frustrating for owners, but it also helps clarify the goal.

The goal is not cure.

The goal is safe management, slower functional decline where possible, better farrier handling, reduced stress, and good quality of life.

Management of Shivers in Horses

Management should be practical and individual.

Keep the Horse in Consistent Work

Regular, appropriate movement appears to help many horses. UC Davis recommends a consistent fitness program, access to turnout, and limited time in a stall, because movement has been reported to minimise clinical signs. (Center for Equine Health)

This does not mean hard work fixes shivers. It means prolonged inactivity can make some horses stiffer, weaker, and more difficult to handle.

Good options may include:

• Regular turnout

• Daily walking

• Light hacking

• Consistent flatwork if safe

• Avoiding long stall confinement

• Maintaining hindquarter strength

• Avoiding sudden workload changes

Reduce Stress and Excitement

Stress and excitement can trigger or worsen episodes. UC Davis specifically notes that stress and excitement can cause shivers episodes, and reducing those triggers is part of management. (Center for Equine Health)

Practical steps include:

• Calm handling

• Predictable routines

• Avoiding rushed farrier appointments

• Avoiding crowded or chaotic environments

• Allowing extra time for travel and competition

• Avoiding punishment when the horse struggles

A shivers horse that panics during handling will usually become harder to manage, not better.

Identify Individual Triggers

Common triggers include:

• Backing

• Hind foot lifting

• Shoeing

• Stress

• Excitement

• Cold weather in some horses

• Fatigue

• Prolonged standing

• Transport

• Sudden routine changes

Write down when episodes occur. Trigger logs can help you adjust handling and reduce risk.

Optimise Nutrition

There is no proven shivers diet that cures the disease.

However, nutrition still matters. UC Davis notes that your veterinarian may recommend vitamin E and selenium supplementation. It also notes that research suggests vitamin E, which supports nerve and muscle tissue, may be important in at-risk horses. (Center for Equine Health)

Practical nutrition steps:

• Feed a balanced diet

• Test vitamin E in horses with limited pasture access or neurologic signs

• Avoid random high-dose selenium unless deficiency is confirmed or likely

• Investigate PSSM separately if signs suggest muscle disease

• Use low-NSC, higher-fat feeding only when there is a clear reason, such as concurrent PSSM or metabolic need

Vitamin E can be helpful when deficient. It should not be sold as a guaranteed shivers treatment.

Farrier Care for Horses With Shivers

Farrier care is often the biggest management challenge.

A horse with shivers may:

• Snatch the hind limb up

• Tremble while the foot is held

• Struggle to hold the limb flexed

• Slam the foot down

• Become anxious as the session continues

• Be worse on one side

• Be worse when shoes are nailed or hammered

• Fatigue quickly

UC Davis notes that farrier work can become increasingly challenging and that sedation with xylazine or detomidine may provide some relief during shoeing. (Center for Equine Health)

Practical farrier strategies include:

• Use an experienced, patient farrier

• Schedule extra time

• Work in a quiet area

• Keep the horse on non-slip footing

• Avoid holding the hind limb high or far back

• Keep the limb low and close to the horse

• Use frequent breaks

• Trim in shorter stages if needed

• Use a helper to keep the horse relaxed

• Consider stocks for safety if available

• Discuss sedation with your vet before unsafe appointments

• Avoid punishment when the horse loses control of the limb

Safety matters for everyone. A shivers horse can slam a hind foot down without warning. That is dangerous for the farrier, the handler, and the horse.

Should Sedation Be Used for Farrier Work?

Sometimes, yes.

Sedation may help when the horse cannot safely hold the hind feet or when the farrier is at risk. UC Davis specifically mentions xylazine or detomidine as options that can provide some relief during shoeing. (Center for Equine Health)

Sedation should be planned with your vet because:

• The drug choice matters

• The dose matters

• The horse’s safety matters

• Sedation can alter balance

• A sedated horse may still react

• Stocks or a safe trimming area may still be needed

• Some horses need a medical review before sedation

Do not sedate without veterinary guidance. A wobbly, sedated, anxious horse with a hind limb in the air is not a brilliant life choice.

Can Horses With Shivers Still Be Ridden?

Many mildly affected horses can continue to work, sometimes at a high level.

UC Davis notes that many horses, especially mildly affected horses, can train and perform at high levels. Horses that are severely affected or that show signs early may experience declining performance over time. (Center for Equine Health)

Riding may be reasonable when:

• The horse is safe

• Forward movement is normal

• There is no significant weakness

• There is no ataxia

• The horse is not falling or stumbling

• The horse is comfortable

• Farrier care remains manageable

• Work does not trigger severe episodes

Reduce or stop ridden work if:

• Signs occur during forward movement

• The horse becomes weak behind

• The horse stumbles or falls

• The horse struggles with turns

• The horse becomes unsafe

• The horse is losing hindquarter muscle

• The horse becomes stressed or distressed by work

The horse’s job may need to change over time. A horse that can hack comfortably may not be suitable for high-level collection, jumping, reining, or any discipline requiring intense hindlimb precision.

What Should You Do Right Now?

If you suspect shivers:

1. Record Video

Video the horse:

• Walking forward

• Trotting forward if safe

• Backing up

• Picking up each hind foot

• Turning sharply

• During a farrier-type hind limb hold, only if safe

Do not force a horse through a dangerous episode just to get footage.

2. Book a Veterinary Assessment

Ask your vet for a neurologic and lameness evaluation. The aim is to confirm whether the pattern fits shivers and rule out pain, stringhalt, PSSM, HYPP, EPM, wobblers, and other conditions.

3. Tell Your Farrier Early

Do not surprise the farrier with a horse that cannot safely hold a hind leg. Build a plan before the next appointment.

4. Avoid Punishment

The horse is not choosing the abnormal movement. Punishment usually increases stress, which may worsen episodes.

5. Keep the Horse Moving

Unless your vet says otherwise, avoid prolonged stall rest. Aim for consistent turnout and regular light work if the horse is safe.

6. Review Diet and Supplements

Make sure the diet is balanced. Ask your vet whether vitamin E testing or supplementation is appropriate. Investigate PSSM only if the signs fit.

7. Track Progression

Keep notes on:

• Backing ability

• Farrier difficulty

• Hindlimb episodes

• Triggers

• Exercise tolerance

• Weakness

• Muscle loss

• Safety under saddle

Shivers progression can be slow, so written notes and videos are more useful than memory.

What Not To Do

Avoid these common mistakes:

• Do not assume the horse is being naughty.

• Do not force the hind leg higher or farther back.

• Do not punish the horse during an episode.

• Do not diagnose shivers without watching the horse back up.

• Do not ignore pain or lameness that could mimic shivers.

• Do not assume every trembling horse has shivers.

• Do not rely on one supplement as a cure.

• Do not keep the horse in prolonged stall rest unless medically necessary.

• Do not let farrier work become unsafe without discussing sedation, stocks, or modified handling.

• Do not breed affected horses without serious veterinary and genetic counselling, especially given the suspected genetic component.

The biggest mistake is treating a neurologic movement disorder like a behaviour problem. That usually makes the horse more anxious and everyone less safe.

Prevention: Can Shivers Be Prevented?

There is no proven way to prevent shivers.

A genetic predisposition has been suggested because of breed patterns, but no specific causative gene has been identified. UC Davis notes that no specific cause has been identified, although a genetic predisposition has been suggested. (Center for Equine Health)

Practical prevention is more about early recognition and safe management:

• Avoid breeding decisions that ignore suspected inherited risk

• Watch young tall horses for backing or hind foot handling problems

• Keep horses fit and moving

• Avoid long periods of stall confinement where possible

• Maintain good farrier handling from early training

• Manage stress carefully

• Investigate early farrier difficulty rather than labelling it behaviour

• Rule out treatable conditions that mimic shivers

You may not be able to prevent shivers, but you can often prevent unsafe handling, delayed diagnosis, and avoidable stress.

Myth vs Reality

Myth	Reality
Shivers means the horse is cold or scared.	True shivers is a neurologic movement disorder, not ordinary trembling.
A horse with shivers is just bad for the farrier.	Many affected horses physically cannot control the hind limb normally when it is lifted.
Shivers is the same as PSSM.	Shivers is neurologic. PSSM is a muscle metabolism disorder. They are different, although a horse can have both.
A supplement can cure shivers.	There is currently no cure. Nutrition may support the horse, especially if deficiencies are present, but it does not reverse the disorder.
If a horse hyperflexes when you pick up the foot, it has shivers.	Not necessarily. A true shivers diagnosis requires signs while backing up. Pain and orthopaedic issues can mimic hind foot lifting problems.
Shivers means immediate retirement.	Many mildly affected horses can continue work for years, but safety and progression must be monitored.

FAQs About Shivers in Horses

Is shivers in horses painful?

Shivers is primarily a neurologic movement disorder rather than a classic pain condition. However, affected horses can become stressed, fatigued, anxious, or sore, and they may also have separate pain conditions such as hock, stifle, back, hoof, or suspensory problems.

Can shivers be cured?

No. There is currently no specific treatment or cure for shivers. Management focuses on consistent exercise, turnout, stress reduction, trigger control, farrier safety, and ruling out other treatable conditions. (Center for Equine Health)

How do vets diagnose shivers?

Vets diagnose shivers by observing characteristic signs, especially abnormal hindlimb movement when backing up, and by ruling out similar conditions through neurologic and lameness examinations. There is no single definitive live-horse test. (Center for Equine Health)

Can a horse with shivers still be ridden?

Many mildly affected horses can continue useful work if they are safe, comfortable, and normal moving forward. Horses with worsening weakness, signs during forward movement, unsafe behaviour, or major farrier difficulty may need reduced work, discipline changes, or retirement.

What helps horses with shivers?

Consistent exercise, turnout, minimising stall time, reducing stress, identifying triggers, careful farrier handling, and veterinary-guided sedation for difficult shoeing may help manage affected horses. Vitamin E and selenium may be discussed with your vet, especially if deficiency is possible. (Center for Equine Health)

The Bottom Line

Shivers is a progressive neurologic movement disorder that most often shows itself when a horse backs up or has a hind foot lifted.

It is not ordinary shivering. It is not simply bad behaviour. It is not the same as PSSM. Current research points toward cerebellar Purkinje cell axon degeneration affecting movement coordination during specific tasks. (PubMed)

The most important practical signs are difficulty backing, hindlimb trembling, hyperflexion, hyperextension, and farrier difficulty involving the hind feet. The most important diagnostic step is ruling out other causes, especially pain, stringhalt, PSSM, HYPP, EPM, and cervical or neurologic disease.

There is no cure, but many horses can be managed well with consistent movement, turnout, calm handling, trigger reduction, thoughtful nutrition, and a safe farrier plan. Mild cases may continue to work for years. Severe cases require more caution because farrier work, handling, and riding can become unsafe.

The best thing you can do is recognise the pattern early, stop blaming the horse, and build a management plan around what the nervous system can and cannot do.

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If your horse struggles to back up, snatches a hind leg away, trembles during farrier work, or may have shivers, ASK A VET™ can help you organise videos, signs, trigger patterns, and questions to discuss with your treating veterinarian.