Horse Side Vet Guide ®

Equine Health Resource

Localized Muscle Loss in an Area

Code Yellow - Contact Your Vet at Your Convenience for an Appointment

Code Yellow - Contact Your Vet at Your Convenience for an Appointment

    Occasionally, a horse develops a local area of muscle loss resulting in an obvious divot or depression in the body corresponding to that muscle.

    Muscle groups are innervated by (the nerve supply comes from) specific nerves. If anything interferes with the nerve pathway to a muscle, then the muscle will waste away (atrophy). Damage to spinal cord, nerve roots, nerves and motor end plates (the connection of nerve to muscle) can all result in local muscle loss. Common causes include traumatic nerve damage, EPM, and other neurologic diseases.

    Sometimes a muscle group seems less developed on one side. Just like humans, horses tend to have a dominant side, and subtle differences can exist in left and right side muscle development. Training or riding that is one-sided or off balance can also contribute to uneven muscle development.


    Assess your horse’s general health using the Whole Horse Exam (WHE), looking for any other abnormalities including any other areas of muscle loss and any patchy sweating in the areas. Watch the horse in movement, looking carefully for any wobbliness, tripping or apparent lameness.

    Carefully compare the affected area to the opposite, apparently normal side. Whenever you are looking for symmetry or asymmetry, be sure that the horse is standing on a level surface, and the limbs are placed as square and symmetrically as possible. Use your hands and your eyes and repeatedly compare the two sides to one another.

    Contact your vet with your findings and concerns.


    Your vet will try to determine the cause for localized muscle loss using physical, neurologic and other clinical exams.

    Author: Doug Thal DVM Dipl. ABVP


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