Equine Health Library

Performance Horse

Health Conditions

Musculoskeletal | Endocrine | Other Concerns


Prevention is key. Maintenance and early detection through an ongoing partnership with a licensed veterinarian will lead to optimal outcomes. Small problems that go undiagnosed or untreated may result in larger issues that could limit a horse’s performance career.

When a performance or training issue arises, start looking for a physical reason before a behavioral one. You’ll want to work with an experienced veterinarian who is familiar with your discipline and its common physical conditions. Many veterinarians who specialize in performance horse practice are familiar with multiple disciplines and skilled in treating horses that perform at the highest levels of competition.

Diagnostic tools

The diagnostic and treatment options available to manage musculoskeletal conditions have expanded significantly in recent years, which means a definitive diagnosis is available now more than ever before.

Digital Radiography

Digital radiography has evolved over the past 10 to 15 years to become a very useful tool in diagnosing musculoskeletal abnormalities and bony lesions. This technology involves projecting a digital radiographic image onto a computer screen. While X-rays have been used for years in veterinary medicine, digital radiography brings many benefits to the veterinarian and, ultimately, the equine patient. Ease of use, instantaneous results, and more sophisticated images that are more detailed with better clarity are just some of the added benefits.

Ultrasound Technology

Ultrasound technology started in equine veterinary medicine as a diagnostic technique for evaluating the reproductive tract (uterus, ovaries) and is now best used for soft tissue abnormalities such as tendon and ligament lesions on the lower legs. Ultrasound has been used to diagnose many conditions involving the heart, lungs, intestinal tract and musculoskeletal disorders.

This technology uses sound waves that are transferred via a handheld probe over a specific body region. Different body tissues reflect the sound waves at specific frequencies, thus producing a digital image. In general, bone will reflect as white, liquid will reflect as black and other soft tissue structures like tendons and ligaments will be somewhere in between. High-resolution ultrasound probes can now produce very detailed images. Ultrasound is also used to perform certain procedures where anatomical placement is essential, such as ultrasound-guided needle aspiration or injection. The ease of this technology also lends itself to routine follow-ups and monitoring healing.

Magnetic Resonance Imaging (MRI)

MRI is the latest and one of the most sophisticated diagnostic tools to advance equine veterinary medicine. Magnetic fields are utilized to generate a three-dimensional cross-sectional view of a specific anatomical area. This technology is superior to both ultrasound and X-rays in that it gives exceptional detail of both soft tissue and bony lesions in one image.

Two types of MRI exist in veterinary medicine today: Standing units and high-power recumbent units. The standing units have the benefit that they can be used on a standing, sedated horse so the horse does not have to be put under general anesthesia. However, the disadvantage is that only the distal limb (hoof, pastern and fetlock) can be imaged. With the horse under general anesthesia, the high-powered units can image fetlocks, carpi, hocks, skull and even stifles (in young horses).

MRI can oftentimes diagnose conditions that are not found by routine X-ray or ultrasound and can even diagnose pathology sooner due to the quality of the image. This early lesion detection can be very beneficial in a performance horse where treatment can be instituted earlier, therefore leading to a better prognosis and outcome of resolution.

Bone Scan

Nuclear Scintigraphy, or bone scan, has been available for approximately 20 years and has been helpful in identifying areas of active inflammation and bone remodeling. This technology utilizes radioisotopes that are injected into a horse via the bloodstream. The isotopes go to areas of active inflammation or bone remodeling. A gamma camera is then used to scan the entire horse’s body to image the areas where the isotopes have been taken up. Multiple images can be generated at one time.

Bone scans are particularly helpful in diagnosing axial skeleton lesions such as vertebral or pelvic fracture. They are also good for difficult lamenesses or suspected fractures that cannot be imaged by X-rays. The disadvantages of this technology are that it requires time and usually an overnight stay at a referral hospital since the horse will be excreting radioactive material for up to 24 hours after injection.

Recurrent Exertional Rhabdomyolysis (RER)

Tying up, is also referred to as recurrent exertional rhabdomyolysis (RER) and describes severe cramping of large muscle groups associated with exercise. While RER isn’t completely understood, it may be caused by a defect in calcium regulation.

Episodes of RER often occur after a fit horse is returned to work or heavy exercise after a period of stall confinement or rest. Tying up can also occur when unfit horses are suddenly asked to over-exert themselves.

Risk Factors

  • High-grain diet
  • Stress
  • High-strung or excitable/nervous temperament

Clinical Signs

  • Reluctance to move
  • A stiff or stilted gait
  • Firm and painful muscles
  • Elevated heart rate, breathing rate and temperature
  • Passage of red-brown discolored urine

Severe episodes require immediate veterinary care. Therapy includes intravenous fluid therapy, administration of analgesics, anti-inflammatory drugs, tranquilizers or sedatives, and muscle relaxants in addition to rest. If you feel your horse is tying up, do not force the horse to move. Call your veterinarian immediately.


Some of the more common hormonal disorders in adult horses affect the adrenal glands, thyroid gland and the pancreas. Addison’s Disease is caused by a deficiency of adrenal gland hormones and is seen only occasionally in horses. Diabetes can also be found in horses, though rare. Similar to the disease in humans, it is a chronic disorder caused by either a deficiency or resistance to insulin. Goiter is another potential endocrine issue in horses. It is a noncancerous enlargement of the thyroid gland that most often develops when there is not enough iodine in the horse’s diet.

Equine Metabolic Syndrome (EMS)

EMS typically affects those breeds considered to be “easy keepers” and includes horses, and more commonly ponies, between the ages of five and 15 years. The syndrome is characterized by obesity, insulin resistance (similar to type-II diabetes in humans) and propensity for recurrent bouts of laminitis that often occur following ingestion of forages and feeds containing high amounts of non-structural carbohydrates (NSC).

Signs Horse is Predisposed to EMS

  • Easy keeper.
  • Unusual fat deposits in the neck (i.e., cresty neck), behind the shoulders, over the eyes and around the tail head. This unique distribution of fat deposits is referred to as “regional adiposity.”
  • Commonly affected breeds: Ponies, Arabians, American Saddlebreds, Morgans, Paso Finos, Spanish Mustangs and Warmbloods.
  • Genetics and environment are contributing factors.

Equine Polysaccharide Storage Myopathy (EPSSM)

Equine Polysaccharide Storage Myopathy is a metabolic disease that results in large amounts of glycogen and abnormal polysaccharide (a class of carbohydrates such as starch) accumulating within skeletal muscle fibers. Thought to be inherited, this disorder is more common in Quarter Horses and Quarter Horse crosses, Paints, Warmbloods and related breeds, draft horses and draft crosses.

Affected horses have unusually large amounts of glycogen stored within their muscles in addition to a large depot of an abnormal polysaccharide. An enzyme deficiency contributes to the deposition of an abnormal polysaccharide that cannot be broken down and used for energy by the muscle fibers during exercise.


Early diagnosis optimizes a successful outcome. Draft breeds that have progressed to recumbency have the poorest chance for recovery. A diagnosis of EPSSM is confirmed through evaluation of appropriate muscle biopsies. Affected horses also have unusually elevated concentrated blood levels of muscle enzymes following even light exercise.

Clinical signs of EPSSM

  • Pain
  • Weakness
  • Muscle spasm
  • Stiffness
  • Loss of muscle mass (atrophy)
  • Severe muscle weakness can result in an inability to rise

Even light exercise can result in exertional rhabdomyolysis (tying up) in horses affected with EPSSM.

Signs of Tying Up

  • Severe muscle pain
  • Stiff gait
  • Reluctance to move
  • Firm, swollen muscles
  • The muscles of the rump, thigh and back are most commonly affected

If your horse ties up, the best thing to do is to keep your horse quiet and call your veterinarian immediately. These tying-up episodes can be sporadic or can occur every time the horse is ridden. Draft breeds often experience more severe episodes leading to recumbency with inability to rise. Chronic cases tend to show generalized muscle wasting over the rump and hind limbs.

Treatment of EPSSM

After a veterinary evaluation and diagnosis, treatment of an EPSSM horse focuses on managing the diet and a controlled exercise program.

  • Affected horses benefit from diets that minimize carbohydrates and maximize fat
  • With these guidelines in mind, you should remove grain, sweet feeds and molasses from your horse’s diet
  • Fat supplements and high-quality forages (alfalfa and alfalfa/grass mix) are essential dietary components
  • Prolonged periods of stall rest should be avoided and replaced with daily turn out
  • When exercising, it helps to warm up and cool down at a walk for 15 minutes each


Our horses may not be able to verbally tell us they are in pain, but most horse owners know when something is not right because they are familiar with their horse’s normal behaviors. In some cases, it is easy to observe that a horse is experiencing pain. However, in other cases, it may not be as obvious. Horses differ in their tolerance of pain and in their outward signs of pain.

Identifying Pain in Your Horse

Individual pain tolerance and how a horse shows us pain may also vary based on such factors as the horse’s age, previous experiences and environment. Some non-painful stimuli, such as anxiety and fear, may also cause similar signs as pain, making recognition of pain in horses a challenge.

Here are some classic signs to look for:

  • Elevated heart rate
  • Elevated respiratory rate
  • Sweating unexpectedly
  • Dilated pupils
  • Behavioral changes – a docile horse may become agitated
  • Ear position – ears partially or fully back (not necessarily pinned) may be an indication of discomfort 
  • Lameness, changes in movement
  • Visceral signs (colic) – pacing, rolling, pawing, or kicking at their sides

Types of Pain

Pain can be classified by whether it involves certain tissues, like superficial structures (e.g., skin), the musculoskeletal system (e.g., muscle, tendon, bone) or visceral tissues (e.g., intestines). Some examples of conditions that may cause pain are of the musculoskeletal system include osteoarthritis, laminitis, navicular disease and a bowed tendon. Colic is the most common clinical sign of pain that originates in the intestines or abdomen.

Pain is also classified as to its duration, normally either acute or chronic. Successful management of acute pain can help reduce the intensity and duration of chronic pain.

Pain Management

One of the most common origins of pain is the normal body response of inflammation. The hallmarks of inflammation are pain, heat, swelling and redness. Inflammation can result in pain in several ways, including the release and presence of chemical mediators (like prostaglandins), which is normal after tissue is damaged. Blocking or inhibiting the production of these chemicals by using non-steroidal anti-inflammatory drugs (NSAIDs) is one strategy used to moderate inflammation and manage acute or chronically active pain.

Management of pain generally includes a variety of strategies and therapies and is dependent on many factors, including whether the pain is acute or chronic.

Acute Pain

Acute pain is of short duration and is generally due to a sudden illness or injury. Examples could include a tendon injury, being kicked by another horse or the abdominal pain of a sudden colic episode. It also includes pain associated with surgical procedures. The treatment goal is to keep the horse comfortable while it recovers and minimize the risk of additional health problems caused by any acute pain.

Early, effective treatment and control of acute pain can reduce the likelihood of transitioning into a state of chronic pain. Successful treatment of acute pain stimuli can also help avoid what is known as the “wind-up effect.” This wind-up phenomenon can occur with continuous, ineffectively treated pain such that the presence of pain becomes more and more difficult to manage. Increased and additional medications may be needed, yet become unsuccessful, when confronting these situations.

First aid for an acute injury may include ice, rest, medications and bandages. As part of the first-aid plan, and afterward, pharmaceutical management is probably the best-known strategy to manage acute pain and inflammation. The goal of medical management is to provide pain relief but maintain the horse’s protective behaviors. For example, it’s important not to mask pain that has a protective mechanism (e.g., limb fracture). Medical care should not make the situation more dangerous for the horse or the owner.

There are several drug classes that are often considered depending upon the type and severity of pain. Acute pain associated with colic, for example, often responds well to the NSAID flunixin meglumine (Banamine® (flunixin meglumine paste)), the synthetic opioid butorphanol (Dolorex® (butorphanol tartrate injection)) and systemic alpha-2 agonists like xylazine or detomidine, both of which have profound sedative and pain-relieving effects in horses.

Chronic Pain

Chronic pain persists for extended periods of time and may not be directly associated with a single contributing event. Examples include osteoarthritis, chronic laminitis and navicular disease. Performance horses often experience chronic pain due to the wear and tear of training and competing at a high level.

NSAIDs are commonly and successfully used to manage chronic pain. Phenylbutazone “bute” is an NSAID often used for long-term pain management because it works well for musculoskeletal inflammation and pain and is cost effective. Properly managed dose and frequency of use can minimize concerns for any NSAID use. Guidance and regular consultation by your veterinarian is the best way to use this family of medications. Horses that eat and drink normally typically do well on bute. However, horses with known gastric ulcers may do better on an NSAID like firocoxib.

Most horses tolerate NSAIDs quite well; however, as with any drug, these products should be used and monitored appropriately. Horses with known sensitivities to NSAIDs may do well with alternate pain management protocols, which may involve nutritional and behavioral adjustments, as well as complementary and alternative therapies such as acupuncture, massage, chiropractic care or shock wave therapy.

There are also local and regional treatment options that your veterinarian may recommend for reducing inflammation and enhancing healing. If the exact location of the horse’s musculoskeletal pain is known, diclofenac (Surpass®) is an NSAID that can be applied topically. For joints and other synovial locations, inflammation and pain management may include hyaluronate (e.g., Legend®), polysulfated glycosaminoglycan (e.g., Adequan®), stem cell therapy and other biologic therapies (e.g., Interleukin Receptor Antagonist Protein (IRAP), Platelet Rich Plasma (PRP)), as well as steroid injections. Every horse is different and will require an individualized pain management approach designed by your veterinarian.

Important Safety Information

BANAMINE: For Oral Use in Horses Only. Not for use in horses intended for human consumption.  Do not use in horses showing hypersensitivity to flunixin meglumine. The effect of BANAMINE Paste on pregnancy has not been determined. Concomitant use of Banamine with other anti-inflammatory drugs such as NSAIDs and corticosteroids should be avoided or closely monitored.  For complete information on Banamine® Paste, see accompanying product package insert.

DOLOREX: FOR USE IN HORSES ONLY. DO NOT USE IN BREEDING HORSES, WEANLINGS, FOALS, AND IN HORSES INTENDED FOR HUMAN CONSUMPTION. DOLOREX is a potent analgesic that should be used with caution with other sedative or analgesic drugs as these are likely to produce additive effects. The most commonly observed side effect was slight ataxia lasting from 3 to 10 minutes. 1.5% of horses underwent marked ataxia and 9% had mild sedation with the use of this drug.  For complete safety information please read label.

Reproductive Health: Show Mares

If you’ve ever used the term “bad mare day,” you know the frustrations that can come with showing a mare in heat. Many trainers of performance mares opt to control the estrous cycle through the use of hormone therapy.

Signs of a Mare in Heat

  • Tail flagging
  • Urination
  • Vocalization
  • Winking
  • Pheromone communication

These behaviors are demonstrated by mares while in estrus for five to eight days during the 21-day cycle and are mediated by the hormone estrogen. If this period of time corresponds with performance or critical training activities, undesirable estrous behavior can be distracting. Elimination of this estrous behavior is naturally accomplished after a mare ovulates and estrogen is replaced with the hormone progesterone, which is produced by the mare’s ovaries during di-estrus.

Regu-Mate® (altrenogest)

This result can be duplicated with Regu-Mate® (altrenogest), a synthetic form of progesterone called progestin. Within three days of the start of treatment, Regu-Mate will effectively suppress estrus in 95 percent of mares. When use of Regu-Mate is discontinued, mares will return to estrus, or come into heat, within four to five days.

Regu-Mate is the only FDA-approved drug for suppression of estrous behavior in the mare.

  • Start with an ultrasound examination of the reproductive tract by a licensed veterinarian familiar with the equine reproductive practice. This should ensure the proper scheduling and optimization of Regu-Mate.
  • During natural estrous cycles, mares return to estrus three to five days after progesterone declines. This same course of events is expected when using Regu-Mate. After discontinuing use of Regu-Mate for four to five days later, the mare will begin to show estrus as a normal, expected result.
  • You can synchronize estrus to plan an embryo transfer during the mare’s performance career or a naturally carried pregnancy at the end of her career. This planned breeding can allow for reproductive performance and maximizes scheduling efficiency while maintaining athletic performance.

Download the Better Mare Management Brochure

Important Safety Information

Regu-Mate® is contraindicated for use in mares having a previous or current history of uterine inflammation. Natural or synthetic gestagen therapy may exacerbate existing low-grade or “smoldering” uterine inflammation into a fulminating uterine infection in some instances. Do not use in horses intended for human consumption. Avoid skin contact. Regu-Mate® is absorbed through unbroken skin, and exposure may result in serious side effects to both women and men. Wear vinyl, neoprene, or nitrile gloves when handling or administering Regu-Mate®, or when touching contaminated surfaces or equipment. Latex gloves are not protective. PREGNANT WOMEN OR WOMEN WHO MAY BE PREGNANT SHOULD NOT HANDLE REGU-MATE®. WOMEN OF CHILDBEARING AGE SHOULD EXERCISE EXTREME CAUTION WHEN HANDLING THIS PRODUCT.  Regu-Mate® is readily absorbed through the skin and could lead to a disruption of the menstrual cycle or prolongation of pregnancy. Accidental spillage on the skin should be washed off immediately with soap and water. Keep out of the reach of children. For complete safety information, refer to the product label.


Before a horse enters strenuous training, ask your veterinarian for a cardiac exam. Careful auscultation of the heart is critical to ensure there are no signs of underlying heart disease (e.g., loud murmur or irregular heartbeats) that could be exacerbated by an intensified workload.

Heart Problems

  • Aortic rupture occurs unexpectedly and is usually a fatal event. The aorta is the large artery that carries blood away from the heart, specifically from the left ventricle of the heart. The risk factors for this condition are not completely understood, but older horses – particularly males – are predisposed. Strenuous exercise often precedes an aortic rupture. Older breeding stallions are at risk soon after breeding a mare. Initial signs may mimic colic since affected horses can appear distressed and uncomfortable prior to collapsing due to blood loss. Other signs include rapid breathing and heart rates. Suggested causes for aortic rupture include congenital aortic aneurysm (wall defect present at birth; considered most likely predisposing cause), vessel wall damage from migrating parasites and vessel wall weakening secondary to copper deficiencies
  • Atrial fibrillation is a type of cardiac arrhythmia that is characterized by an irregular heartbeat and decreased cardiac output. The atria comprise two of the four chambers of the heart, and when they contract, they send a signal to the other chambers (the ventricles) to contract next. During atrial fibrillation, the atria begin to contract rapidly, sending multiple signals to the ventricles to contract. This is a malfunction of the electrical system of the heart. Atrial fibrillation is the most common performance-limiting arrhythmia in the performance horse
  • Murmurs are heart sounds that are abnormal and can be detected during a routine physical exam. Murmurs are heard where periods of silence should be and functionally represent leaky valves within the heart. The clinical significance of murmurs can be determined by further diagnostic testing, including an electrocardiogram (ECG) and echocardiography. Not all murmurs are performance-limiting


Performance horses are more likely to receive a variety of antibiotics and/or pain medications during the course of their athletic career. Certain antibiotics and non-steroidal pain medications can cause kidney disease, especially if the horse receiving these drugs is dehydrated.

Clinical signs of kidney disease can be subtle or dramatic. With some forms of kidney disease, horses become depressed, lose their appetite and begin to lose weight. Depending on the cause and chronicity of the kidney disease, urine production may be increased or decreased.  Horses that are urinating larger volumes more frequently often begin to consume more water.

Blood work frequently reveals elevations in creatinine and BUN (blood urea nitrogen) together with derangements in electrolyte concentrations. 

Treatment for kidney disease depends on the cause and whether the condition is acute or chronic.