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


Bubble of Soft Swelling on Outside &/or Front of Hock


The equine hock is equivalent to your ankle. It is made up of many bones, four joints and several tendon sheath - a complicated anatomy.

"Bubbles" of fluid accumulation around the hock can indicate fluid accumulation within specific joints or tendon sheaths. Each of these accumulations means something different for the health of the horse.

A firm fluid accumulation on the outside (lateral) upper part of a horse’s hock is commonly known as a "thoroughpin". It is a fluid-filled swelling within the flexor tendon (tarsal) sheath that encloses the flexor tendons as they run through the hock.

A “bog” is the horseman's term for a fluid accumulation within the top joint of the hock, which is found lower and a bit further forward than a thoroughpin and is also visible at the front of the hock.

For any of these swellings, the horse may or may not be lame, as accompanying lameness depends on the nature of the underlying cause.

  • Code Orange

    Call Your Vet at Their First Available Office Hours
    • If you notice lameness in addition to this sign.
    • If you feel the problem is severe or has come on suddenly.
  • Code Yellow

    Contact Your Vet at Your Convenience for an Appointment
    • If you do not notice lameness or pain, only a swelling.
    • If the swelling is mild or moderate, and not increasing rapidly.

your role


What To Do

Monitor the horse for lameness and change in the appearance of the swelling over time. Compare the swelling on the affected leg to the other leg. Assess your horse’s general health using the Whole Horse Exam (WHE), and call your vet with your findings and concerns.

If you are considering the purchase of the horse, always have your vet perform a purchase exam. In that exam, they determine the significance of these swellings.

What Not To Do

Do not assume that a "bog" or "thoroughpin" (or any other swellings in this area) are benign and can be ignored. Sometimes they result from an underlying disease that requires diagnosis and treatment.

NEVER purchase a horse with a swelling here without a veterinary pre-purchase exam!

your vet's role

Your vet's role is to determine the significance of the swelling by identifying the underlying cause - a diagnosis. Only then can they tell you what you what it means to you and your horse, including a recommendation regarding treatment and a prognosis.
Questions Your Vet Might Ask:
  • What is the age and breed of the horse?
  • Is the horse limping or lame?
  • If the horse is lame, how lame?
  • When did you first notice the swelling?
  • How does the swelling compare to the opposite limb?
  • What does the horse do for a living?

Diagnoses Your Vet May Consider

The cause of the problem. These are conditions or ailments that are the cause of the observations you make.

Very Common
Less Common
more diagnoses

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

Author: Doug Thal DVM Dipl. ABVP