Tying-Up in Horses: When Muscle Pain Requires Veterinary Attention

What Is Tying-Up in Horses?

Every horse owner has heard at least once of tying-up, azoturia, or Monday morning disease. The term holiday disease also became common because tying-up in horses often occurred after rest days followed by heavy work. In the past, working horses were especially affected when they had to return to labor on Monday after the weekend, which is also where the English term Monday Morning Disease comes from.

Tying-up is an acute muscle disorder affecting the horse’s back and hindquarter muscles and outwardly resembles a severe case of muscle soreness. In an acute episode, the horse experiences intense pain and muscle cramping, the muscles in the back and loin area become rock hard, and the horse is often unwilling to move.

➡️ Video Tip: First Aid I: Emergency Tips for Injuries and Lameness
First aid for tying-up in horses. From minute 7:30, you will learn how to react correctly in the event of tying-up and how to support your horse in the best possible way — essential emergency advice for horse owners.

Tying-up in horses is classified as one of the exertional myopathies, meaning muscle disorders that develop in connection with physical exercise. However, there is more behind a case of equine tying-up than simple muscle strain, as we will see below. It can also be divided into two main forms: sporadic tying-up and the chronic, genetic form known as PSSM type 1 and type 2.

Symptoms – How do I recognize tying-up in a horse?

While tying-up used to affect mostly working horses such as carriage horses or pit ponies, today it is seen especially in well-trained sport horses. In the case of acute tying-up, the episode usually starts suddenly at the beginning of exercise after a longer period of rest.

The key sign of tying-up in horses is a horse that is unwilling to move, or physically unable to move because of severe muscle cramping. The horse often stands in a sawhorse stance.

When the symptoms appear and how severe they are depends on the seriousness of the episode. Signs differ between mild, moderate, and severe cases:

Mild tying-up:‍

• Symptoms appear less than 10 minutes after the start of exercise.
• Restlessness.
• A stiff, short-striding gait.
• Especially the hindquarters appear stiff and lame.
• The urine remains straw yellow.

Moderate tying-up:‍

• Symptoms appear 15 to 30 minutes after the start of exercise.
• The horse stops and becomes reluctant to move.
• The horse begins to sweat.
• The muscles of the back and loin area start to cramp.
• Some horses buckle in the hindquarters.
• The urine turns orange to light brown.

Severe tying-up:‍

• Symptoms appear 30 to 60 minutes after the start of exercise.
• The horse is unable to move.
• The horse drops its back and braces its legs forward and backward in a sawhorse stance.
• The hindquarters move only uncontrollably.
• If the horse lies down, it may become unable to get up.
• Heavy sweating, fever, and a racing heart.
• Because of the severe fluid loss, muscle cramps may occur together with colic-like signs.
• The back muscles become rock hard.
• The urine turns brown or even black.

In the worst case, the horse goes down and cannot rise again because of the severe muscle spasms. Without treatment, tying-up can be fatal. The horse may also die from kidney failure if the kidneys become blocked.

Causes of Tying-Up – What causes tying-up in horses?

Although tying-up in horses belongs to the group of exertional myopathies, unlike some other muscle disorders, its cause is rooted in metabolism. It is therefore more accurately described as a metabolic disorder. If the horse is fed too many carbohydrates, which are broken down into glycogen but cannot then be used efficiently, they accumulate excessively in the muscles. Too much glycogen in the muscle tissue interferes with oxygen transport and therefore also with the removal of waste products and toxins. This increasingly acidic environment raises the lactate concentration inside the muscle cells. The result is severe muscle soreness that can progress to the rupture of muscle cells.

As the damaged muscle cells break down, myoglobin is released. This muscle pigment passes into the bloodstream and urine, causing the urine to become discolored. The more muscle cells die, and therefore the more severe the episode, the darker the urine becomes.

So how does the horse end up with too much glycogen in the muscle cells? If the feed ration is not reduced on rest days, for example over the weekend, the energy is not needed. Instead of being useful, it becomes harmful. The cause of an acute tying-up episode therefore usually lies in poor exercise management, stable management, and feeding management.

The Difference Between Tying-Up and Other Equine Myopathies

Acute sporadic exertional rhabdomyolysis (SER) develops as a result of an extreme imbalance between feeding and exercise and occurs especially in horses with well-developed musculature.

There is also recurrent exertional rhabdomyolysis (RER) and the genetic glycogen storage disorder / polysaccharide storage myopathy (PSSM):

If episodes of tying-up occur repeatedly, it may be recurrent exertional rhabdomyolysis (RER). This form is seen more often in mares and Thoroughbreds, especially racehorses. Due to excessive stress, for example strong external stimuli or horse racing, the calcium released during muscle activity can no longer be transported away properly. The horse then shows symptoms similar to those seen in sporadic tying-up.

PSSM is a metabolic muscle disorder that mainly affects heavily muscled American horse breeds such as the Quarter Horse. PSSM type 1 is genetic and can be identified through a hair test. Horses with PSSM store energy in the form of complex polysaccharides that are larger than normal glycogen, and they cannot process them correctly. As with tying-up, affected horses suffer from muscle pain during exercise and often move stiffly, especially at the beginning of work. Horses with PSSM therefore require a particularly long warm-up phase before their muscles begin to relax.

PSSM type 2, now more commonly referred to as MIM (muscle integrity myopathy), is not a single clearly defined disease, but rather a collective term for exertional myopathies that cannot be classified more precisely.

First Aid for Acute Tying-Up

➡️ Video Tip: First Aid I: Emergency Tips for Injuries and Lameness
First aid for tying-up in horses. Dr. Matilda Holmer-Rattenhuber explains which immediate steps you should take in the event of tying-up to help your horse quickly and effectively — essential knowledge for every horse owner.

Rule number one in a tying-up episode: never make the horse keep moving. Any further movement and strain on the muscles can make the condition significantly worse. The horse should be led back to its stall at most. If you are out on a hack and the horse refuses to move, it should be transported back to the stable by trailer.

A veterinarian must be called immediately, because depending on the severity of the episode, every minute can matter. The vet can then administer anti-inflammatory, pain-relieving, and muscle-relaxing medication.

While waiting for the veterinarian, and provided the horse is not overheated, a warm sweat rug can help keep the back and croup area warm and thereby reduce muscle cramping. A gentle massage may also help relieve pain.

Diagnosis and Treatment by the Veterinarian

A veterinarian can diagnose tying-up in horses with a blood test. One of the key values checked is the enzyme creatine kinase (CK). This enzyme is released or activated when muscle tissue is damaged. The higher the value, the more serious the muscle damage. The normal value should generally be below 130 U/l.

If the horse is sweating heavily and urinating a lot, it loses fluid along with important electrolytes. To prevent dehydration and help the muscles relax, the veterinarian may administer an intravenous fluid infusion combined with electrolytes, muscle relaxants, anti-inflammatory medication, and circulation-supporting drugs. In some cases, calcium may also be necessary, as it plays an essential role in muscle contraction and nerve transmission.

Depending on the severity of the tying-up episode, the condition may resolve within a few hours, or the horse may need several weeks to recover. If the illness or recovery period continues for longer, another blood test is usually performed after around two weeks to recheck the values.

After that, and only according to the veterinarian’s instructions, the horse can gradually begin hand-walking at the walk. Standing still for too long is harmful for the horse and can even trigger another episode of tying-up once training is resumed.

The healing phase can be supported with warmth, warm wraps, and massage therapy. These measures provide relief, improve circulation, and promote the removal of metabolic waste products.

Prognosis – Does my horse have a good chance of recovery after tying-up?

If tying-up is recognized early and treated immediately, the chances are good that the horse will recover. The prognosis is less favorable, however, for horses that lie down because of severe cramping and then become down and unable to rise. In severe cases, a horse can die from prolonged recumbency or from kidney failure.

If tying-up occurs repeatedly, it can lead to a long-term metabolic disturbance.

That is why you should act immediately at the very first suspicion and call your veterinarian without delay.

Preventing Tying-Up with Feeding, Exercise, and a Training Plan

The best way to prevent sporadic acute tying-up is through correct management and training:

• Avoid abrupt transitions between rest and intense work.
• Make sure the horse is warmed up and cooled down properly.
• Maintain a consistent routine and avoid stress caused by constantly changing routines or environments.
• Avoid long periods of box rest.
• Adapt the feeding program to the horse’s actual energy requirements.
• Prevent chilling of the back muscles.

Creating a structured training plan for your horse is therefore highly recommended for the prevention of tying-up. It helps establish a balanced relationship between rest and work and makes training more regular and consistent. In addition, you should analyze your horse’s current housing conditions. Regular daily free movement, ideally in open-stable systems with pasture turnout, is crucial for the horse’s health.

Performance diagnostics also play a key role. To learn how fit your horse really is, take a look at the video on performance diagnostics in our ClipMyHorse.TV Academy.

Standing in an open stable, your horse may still benefit from a rug in cold, wet, and windy weather. Muscular tension caused by chilling can also trigger tying-up in horses. After training, make sure that a horse which continues to sweat is covered with a windproof and quick-drying sweat rug until it is completely dry.

Abrupt ration changes and excessive intake of energy, starch, and sugar are major contributing factors in tying-up. Especially on rest days, the feed ration should be reduced or replaced with a lower-energy ration containing less starch and sugar. Replacing part of the carbohydrate intake with fats and oils may also be helpful.

Supplementing with selenium and vitamin E can also be beneficial, as both help protect the muscles against oxidative stress. However, this should always be discussed with your veterinarian beforehand, because both nutrients can be overdosed.

Tying-Up in Horses: The Most Important Questions and Answers

Why does the urine turn brown in a tying-up episode?‍

Waste products and toxins are excreted through the kidneys in the urine. In moderate to severe cases of tying-up, muscle cells begin to die. The muscle pigment myoglobin is released, enters the bloodstream, reaches the kidneys, and is then excreted in the urine. The more muscle cells die, the more myoglobin is released and excreted, and the darker the urine becomes.

How long does a tying-up episode last?‍

How quickly tying-up resolves, and how long the horse should rest, depends on the severity of the condition. In mild cases, the horse may recover within a few hours. In other cases, it can take up to two months before the blood values return to normal.

How long should the horse rest after tying-up?‍

After a tying-up episode, you should rely on your veterinarian’s advice and follow it closely. To determine the severity of the episode, the veterinarian will perform a blood test to measure the level of creatine kinase (CK). The horse should only return to work once the blood values have normalized. The threshold value for creatine kinase is below 130 U/l.

Can tying-up be fatal for a horse?‍

Untreated tying-up can be fatal, for example if the horse goes down and cannot rise again because of severe muscle stiffness. Another possible cause of death is a blocked and exhausted kidney, which can lead to organ failure.

Does a horse with tying-up have to be euthanized?‍

Not every case of tying-up is so severe that the horse must be euthanized. With rapid treatment, the horse usually has a good chance of recovery. In severe cases, however, the veterinarian may decide that euthanasia is necessary.

The best way to prevent tying-up and therefore also the risk of an emergency euthanasia is through regular, balanced exercise and a feeding program that is properly adapted to the horse’s workload.