South Shore Equine Clinic & Diagnostic Center
Equine Veterinary Services South Shore Boston Massachusetts

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Questions & Answers

Question:

  • My horse has swelling around all four fetlock joints. When I asked my trainer about it, she told me that they were “windpuffs”. What are “windpuffs”?

Answer:

Windpuffs is a term that denotes synovial effusion (i.e. extra fluid) within the fetlock joint and/or digital flexor sheath. It can occur in the front legs, the back legs, or both. Extra fluid results in a soft fluctuant swelling behind and just above the fetlock joint. It is more common in older horses, but can occur at any age.

Although the digital flexor sheath and fetlock joint are in close proximity with one another, effusion in one structure can be identified by its specific location. Swelling behind the suspensory ligament branches is consistent with digital flexor sheath effusion. Swelling in front of the suspensory branches suggests fetlock joint effusion.

In the vast majority of cases, the swelling is a result of extra fluid within the palmar (front leg) or plantar (back leg) digital sheath rather than the fetlock joint. The plantar digital sheath acts as a sleeve that houses the superficial and deep digital flexor tendons as they course around the back of the fetlock joint. Normally, a very small amount of synovial fluid is present within the sheath to provide lubrication to the tendons as they slide around the back of the joint.

Excessive fluid within the sheath develops in response to increased hydrostatic pressure which in turn occurs due to the presence of inflammatory cells (inflammation) within the sheath. The synovium can become inflamed for a variety of reasons such as flexor tendonitis, trauma to the synovial membrane, infection, etc. In most cases, however, the source of the inflammation is undetermined.

Although plantar digital effusion can cause clinical lameness, this is rare except in severe cases (e.g. infection or tendon damage). Therefore, the problem is considered primarily cosmetic in nature. Consequently, most horses are left untreated.

Treatment options include intrasynovial injection (steroids/ hyalronan) or surgical debridement. Injection usually dramatically reduces the size of the swelling, although recurrence is very common and usually expected. Surgical manipulation can result in the formation of scar tissue within the sheath, which in turn can cause adhesion formation and lameness. Therefore, this strategy is reserved for only the most severe of cases.

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