Muscle soreness in horses

Is your horse suffering from primary or secondary muscle soreness? Learn the difference between the two, know what signs to look for, and what the treatment options are.

Many of us consider muscle pain to be normal after a long ride — but what about our horses? Do they feel the same muscle soreness we do? How do they display this discomfort, and how can it be treated?

Symptoms and causes of equine muscle pain

A variety of problems can contribute to muscle pain in horses.

• Primary muscle soreness will usually present itself quite dramatically. Symptoms can include muscle stiffness, sweating, reluctance to move, violent tremors, tucked-up abdomen, or even collapse. Primary muscle problems are often due to an improper function of muscle metabolism, sometimes linked to a genetic component.

• Secondary muscle pain can stem from improperly-fitting equipment, foot soreness or arthritis. Symptoms can be seen in behavioral changes such as a reluctance to go forward, bucking, tail swishing, and changes in overall demeanor. As a start, observe and differentiate between primary and secondary muscle problems.

What causes primary muscle soreness?

Primary muscle soreness can be due to a muscle condition such as Polysaccharide Storage Myopathy (PSSM) Type 1 or 2, or Equine Hyperkalemic Periodic Paralysis (HYPP).


PSSM has been documented in over 20 breeds in the last couple of years. It occurs when there is an improper buildup of excess glycogen (the stored version of sugar) in the muscles. Signs of PSSM Type 1 or 2 include muscle stiffness, sweating, reluctance to move, tremors, and a tucked-up abdomen. These symptoms usually occur ten to 20 minutes into a ride. A blood test by your veterinarian will usually reveal an elevated CK level, and a muscle biopsy will show excess glycogen storage. A genetic test is also available using hair roots and blood. PSSM2 affects horses in the same manner, but these horses will not test positive for the gene found in PSSM1. Muscle biopsy is still the most effective way to diagnose both PSSM1 and 2.


HYPP is caused by a genetic defect seen in relatives of Impressive, the quarter horse sire. Excessive potassium levels or stress can cause a dysfunction within sodium channels in the muscle, causing dramatic tremors, weakness or even collapse. Unlike PSSM, these symptoms do not come after exercise but can manifest while the horse is at rest, during transport or a stressful event. Genetic testing is available and treatment includes dietary reduction of potassium, routine turnout, and possible drugs to stabilize potassium and glucose levels.

Secondary muscle pain can stem from several issues

While secondary muscle pain is more common than primary, it can be frustrating to diagnose its exact cause (see below). The multitude of contributing factors include, but are not limited to: poor fitness, dietary deficiencies, improper saddle fit, shoeing problems, or altered movement due to joint pain. This type of pain usually presents as a mild reluctance to go forward; behavioral changes under saddle, such as bucking, spooking or excessive tail swishing; or behavioral changes while being groomed or shod. Keeping this in mind, you can often address and correct some of these problems prior to a veterinarian visit.

3 reasons for secondary muscle pain

1. Saddle fit

Improper saddle fit can be a major contributing factor to muscle pain along the back, withers and shoulders. Has your horse recently lost or gained weight and muscle, or had a change in fitness level? This alters how your saddle fits and can cause pinching under the seat, at the withers, and along the stirrup bars. Symmetry over the shoulders and back can be altered due to poor saddle fit and pinching.

Frequently, clients will say, “It’s the same saddle I have always ridden in!” As riders, we have to understand that horses will continually change their shape and muscle tone, making saddle fit an ongoing battle. Compounding this task is the variation between saddle styles. In both English and Western saddles, you can have endless options of tree sizes, shapes, flocking type and seat styles.

When purchasing a saddle, you should look for one that can be altered if your horse changes shape. This may include a yearly visit from the saddle fitter to ensure no changes need to be made. Creating a custom saddle that fits your horse — and fits with your horse — is a preventative step against muscle pain.

2. Dietary deficiencies

Dietary deficiencies in horses are more common than you would think. Our four-legged athletes need a balanced vitamin and mineral diet to recover and heal properly. A poorly-balanced diet is always contrary to horse health and can be a contributor to post-ride muscle soreness. You may think that because your horse’s weight is perfect, his diet is surely correct. Not in every case.

Feedbags containing complete feed will have a reference chart with the amount necessary to get a balanced diet, including proper vitamins and minerals. Using a weight tape, measure and calculate how much feed your horse will need to achieve a balanced diet with your particular grain. A luggage scale or home food scale is a great way to weigh out the appropriate amount of feed.

If your horse is getting less than the recommended amount of feed, and maintains an ideal weight, you should look into adding a daily ration balancer or vitamin-mineral supplement to his diet. Many feed companies will be happy to guide you through their recommendations for your own horse’s needs.

3. Compensatory movement

Pain related to compensation for a musculoskeletal issue lower in the leg is, by far, one of the main causes of secondary muscle pain. A compensatory movement will alter your horse’s gait, causing muscle soreness in areas of the lower back, deltoids, pectorals and gluteal region. Muscles in this region will either be enlarged from overuse during compensation, or reduced due to muscle wastage from disuse, due to pain lower in the leg.

One of the main complaints from clients is that the saddle slips when they ride. This can be a sign that the horse is having a musculoskeletal issue lower in his leg, causing him to throw his weight to one side when you ride. Stand back, square your horse up and look for symmetry in these areas.

If any of these things sound familiar, you should have a soundness examination done by your veterinarian.

Treating muscle soreness

Treatment for PSSM is mainly environment-based, involving strict dietary changes, including high fat-low starch feeds; exercise routines; turnout; and ration balancer supplements containing high levels of vitamin E. With proper management, a return to work is seen in over 75% of horses diagnosed with PSSM1 or 2.

Treating secondary muscle pain includes finding the source of the problem and alleviating it. This can be followed by spinal manipulation/chiropractic, acupuncture, massage or muscle relaxants. Once the problem has been identified, treatment is critical to reduce pain and prevent its return. Non-invasive options like spinal manipulation/chiropractic and acupuncture will allow your horse to move through his normal range of motion again, and open pathways that allow for healing. Muscle relaxants can be used in combination with these therapies to break the pain cycle in the horse. Remember, these treatments are used to heal and maintain a healthy horse, but will not fix the problem if there is still an underlying issue that needs to be addressed.

Whether he’s suffering from primary or secondary muscle soreness, every horse has a different pain tolerance and can display discomfort in a variety of ways. Listen to what your horse is telling you. Notice his behavioral changes and get to the root of the problem.