What you see. The starting point for addressing any equine health related issue is your observation.


Loss of Shoulder Muscle on Right or Left


Muscle groups are innervated by (the nerve supply comes from) specific nerves. If anything interferes with the nerve supplying a muscle, then the muscle will waste away (called denervation atrophy). Lack of use also causes muscle atrophy.

Obvious localized loss of shoulder muscle may result from a variety of problems including traumatic nerve damage, neurologic diseases, or Sweeney - a condition in which the muscles overlying the shoulder are severely atrophied leading to a hollowed-out appearance. Sweeney is caused by traumatic damage to the suprascapular nerve that runs near the point of the shoulder, usually from a severe blunt impact to that area.

  • Code Orange

    Call Your Vet at Their First Available Office Hours
    • If the horse seems to be in distress.
    • If lameness is noticeable at the walk.
  • Code Yellow

    Contact Your Vet at Your Convenience for an Appointment
    • If you consider this a chronic and relatively mild problem that is not changing rapidly.
    • If the results of the Whole Horse Exam (WHE) suggest the horse is otherwise normal.

your role


What To Do

Assess your horse's general health using the Whole Horse Exam (WHE). Compare the appearance of the shoulder to the opposite side. Assess lameness at the walk. As the horse walks, look for shoulder slippage or popping action around the shoulder that can sometimes result from the lack of stability created by the absence of muscle support of the joint. Contact your vet with your findings and concerns.

What Not To Do

Do not ride a horse that has obvious loss of muscle in the shoulder area without veterinary guidance. The horse could fall.

your vet's role

Your vet will try to determine the cause for this muscle loss using physical, neurologic and other clinical exams. In many cases, they will also recommend a lameness exam. In some cases, they will recommend additional tests.
Questions Your Vet Might Ask:
  • When did you first notice this problem?
  • Is there a history of severe lameness or accident in the horse's past?
  • Can you send me a photo of the problem?
  • What geographic areas has the horse been to in the last 3 years?
  • Has the horse been lame historically?
  • What is the horse's age, sex, breed and history?

Treatments Your Vet May Recommend

A way to resolve the condition or diagnosis. Resolving the underlying cause or treating the signs of disease (symptomatic treatment)

Very Common
more treatments

further reading & resources

Author: Doug Thal DVM Dipl. ABVP