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Joints


The term ‘sepsis’ refers to the presence of pus-forming bacteria within blood or tissues. So joint sepsis simply means: an infection within a joint. This is, however,  a most serious dilemma in the horse.

               Joint infections can result in one of several ways. Most commonly, a wound created from external trauma is located near a joint and extends deep enough to enter into and contaminate that joint sac with bacteria. Another possibility, is when a horse (particularly a newborn foal) has an infection in its bloodstream (septicemia) that is then deposited in various joints and other locations such as visceral organs. The third possibility is if a surgery or joint injection is performed with less than adequate sterility and the joint is inadvertently inoculated with bacteria by a veterinarian. These three possibilities exist, although most commonly, the first scenario is the culprit.

               Horses can get hurt, cut and punctured in a round, padded room. This unique characteristic of the equine is what we equine veterinarians call ‘job security.’ All joking aside, despite our purposeful attention to safe fencing and housing, horses really do get injured frequently, compared to people, dogs or cats.  Many of these injuries come in the form of lacerations and puncture wounds. Lacerations or puncture wounds can be benign entities, or when they enter a joint or tendon sheath, they can be life-threatening injuries, if not managed in a timely and aggressive fashion. Knowing a little bit about your horse’s anatomy can help you make an informed decision about whether or not to call your veterinarian.

A joint or tendon sheath infection that is not addressed properly can result in a severely lame, unusable horse that must be euthanized for humane reasons. This may seem like a harsh statement, but the importance of joint infections can not be overemphasized. Once bacteria is inoculated into a synovial structure, a cascade of events occur that are difficult for veterinarians to overcome if not caught immediately and treated aggressively. The joint and tendon sheath is a closed environment, which means once bacteria is inoculated into the area, it is contained there and allowed to replicate undisturbed.

Most of your horse’s joints and tendon sheaths are located very superficial in relation to the skin surface. This means that even minor lacerations and puncture wounds could involve a synovial structure such as a joint or tendon sheath. So knowing where problem areas are on a horse is very important in this respect.

The most dangerous region for a wound hands down, is from the ankle to the hoof. Within that ten inch section of anatomy, there are more synovial structures (and otherwise important tendons and ligaments) than anywhere else. To be exact, there are three joints, one tendon sheath, and the navicular bursa. Any other area of the horse's limb that bends also has a joint(s) associated with it. And it is sometimes deceiving how remotely a joint sac can be from the actual moving area. Please refer to the diagram below to see the highlighted areas; these areas have joints/tendon sheaths in close proximity.

A joint or tendon sheath infection that is not addressed properly can result in a severely lame, unusable horse that must be euthanized for humane reasons. This may seem like a harsh statement, but the importance of joint infections can not be overemphasized. Once bacteria is inoculated into a synovial structure, a cascade of events occur that are difficult for veterinarians to overcome if not caught immediately and treated aggressively. The joint and tendon sheath is a closed environment, which means once bacteria are inoculated into the area, the infection is contained there and allowed to replicate largely undisturbed. The joint environment is also difficult to get antibiotics to penetrate into at high enough levels to resolve the infection when given orally or via injection. This is a great oversimplification but without diving into the complex pathophysiologic response involving white blood cells, chemical messengers, and the process of cartilage breakdown, the aforementioned information is what we all really need to know.

           

 

Duane Fitzgerald, DVM

 

Please check back soon to see the second part of this article on “Treatments of Joint Infections.”