Conditions or ailments that are the cause of a problem that you see - your observation.

Your vet may diagnose

Septic or Infected Flexor Tendon Sheath (in Adult)

Synonyms: Joint Ill


The tendon sheath is the balloon like structure that encloses and lubricates the flexor tendons slightly above and below the fetlock joint. The digital flexor tendon sheath is present on both front and hind limbs on the rear of the fetlock joint. See the accompanying photo for the location of the normal tendon sheath.

A septic (infected) tendon sheath usually results from a wound that has penetrated into the sheath, most often on the rear of the pastern. Bacteria are introduced into the sheath and proliferate, and a massive inflammatory process follows. More rarely, infection can be introduced during veterinary injection of the tendon sheath. Very rarely (more commonly in foals), bacteria can arrive in the tendon sheath via transport in the blood.

As with any infected synovial (joint or tendon sheath) structure, infection causes severe lameness and swelling and is a life threatening problem. As long as there is a wide open wound and significant drainage, lameness is not as severe. Once the wound heals closed, the tendon sheath becomes a closed "abscess" and the horse is severely lame.

my role


I might observe

You might make these observations when a horse has this condition.

Very Common
Less Common
more observations

Questions To Ask Your Vet:
  • Is there infected bone present within the joint also?
  • How much joint or tendon sheath destruction do you think has already taken place?
  • What are the chances that you are able to clear the infection with the most aggressive treatment protocols versus the less aggressive?

Wounds in this area can be serious, even if they look small and simple. Always call your vet to discuss injuries to this area, especially when accompanied by lameness. Good basic husbandry reduces the likelihood of wounds.

Author: Doug Thal DVM Dipl. ABVP