Joint Injections: What and Why?
Joint injections are a procedure commonly performed by equine veterinarians. Many types of horses, from western performance to racehorses, have joint injections performed. However, not every horse owner knows what is involved in the process, and what we are trying to accomplish with joint injections.
There are two main reasons to "tap" a horse's joint: anesthesia or "blocking" for lameness diagnosis, and medicating the joint (Figure 1). To localize a lameness to a specific area or joint, nerve and joint blocks can be performed. A joint block involves injecting the joint with a local anesthetic like lidocaine for desensitization. If the lameness resolves after injection, it is likely that the joint that was injected is the source of the horse's pain. Joint injections can also be used to administer certain drugs to help the horse (figure 2). Typically, a steroid can be administered into a joint to help combat inflammation that may occur there. Hyaluronic acid, a substance to help lubricate the joint, can be given simultaneously with steroids.
When your veterinarian makes a call to inject your horses' joints, they will go through several steps before they are ready for the procedure. First, adequate restraint is key to a successful and safe joint injection. An experienced handler is necessary because sticking a horse's legs with needles can be very dangerous. If the horse is not going to be still, sedatives may be given to allow the horse to stand quietly for the procedure. Next, the skin where the needle will enter the joint is aseptically prepared. Typically, an antiseptic soap such as iodine or chlorhexidine is used to scrub the skin and alcohol will be used to wipe off the soap. Once the area is clean, it is time for the injection. Your veterinarian will find the location of the joint and quickly but carefully insert a needle. Joint fluid will often be expressed through the needle, and the health of the fluid can be assessed at that time. Drugs will then be administered to treat the joint medically.
When using joint injections as a treatment for your horse, it is important to know the advantages and possible disadvantages of the procedure. Inflamed joints can benefit greatly from injection with steroids. These drugs have a powerful anti-inflammatory effect which can alleviate lameness and improve any joint capsule distention (a "filled joint"). Likewise, hyaluronic acid can be used with a steroid to protect the ever important cartilage within the joint. There is a cost associated with joint injections, but it is often small compared to the effect they can have on your horse's performance.
Joint injections will not resolve all horses' lamenesses because the lameness localized to a particular joint may be originating from the soft tissues surrounding the joint. However, many horses will only need to be injected one or a few times to achieve long term comfort. Sometimes a joint "flares" after injection, which is caused by inflammation that occurs secondary to the injection. However, this is rarely career limiting and can be treated easily with rest and pain medication. Any time you put a foreign object into the body there is a risk of infection, and this is possible with joint injections. However, your veterinarian uses precautions such as scrubbing the skin thoroughly and sometimes injecting antibiotics into the joint at the time of treatment to prevent infection from occurring. Lastly, administration of steroids into the joint can injure the cartilage over time, so it is wise to use joint medications sparingly and only when necessary.
Joint injection is a very important procedure used in veterinary medicine to localize lameness or medicate a joint associated with pain, swelling, and inflammation. Being aware of the uses and side effects of the procedure is vital information for any horse owner. Together, you and your veterinarian can work together to use joint injection as a tool to care for your horse in the best way possible.