The extensor tendon sheaths are balloon-like spaces enclosed by a thin membrane and containing a small amount of synovial fluid (egg yolk-consistency fluid that provides lubrication and nutrition to the tendon). These tendon sheaths are located on the fronts and sides of the highest motion areas in the limb; the carpus in the forelimb and the hock in the hind limb.
Direct trauma to the extensor tendon sheaths causes local swelling over the face of the carpus or hock, usually without much lameness. This is probably most common in jumping horses that hit a jump. There are several tendon sheaths over the face of both the carpus and hock. The particular pattern and location of swelling will depend on which tendon sheath is injured.
In some cases, injury to the tendon itself within the sheath also causes chronic swelling. Fortunately, in most cases these injuries are considered only blemishes. They usually do not cause lameness or reduction in performance.
Veterinary diagnosis requires examination and ultrasound. In some cases, the tendon sheath fluid needs to be sampled.
Treatment depends on the severity of tendon injury and mostly revolves around quieting the inflammation within the space, often with injection of various anti-inflammatory drugs.
Other Diagnoses Considered
Treatments May Include
Prognosis & Relevant Factors
Good, although swelling may persist and result in slight thickening of the area even long term. It can be difficult to completely eliminate swelling.
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Helpful Terms & Topics in HSVGWritten, Reviewed or Shared by Experts in Equine Health