Intra-articular (joint) injections are a seemingly ubiquitous procedure, but there really is a science and an art to the process. Choosing the right combination of diagnostic procedures and treatments is integral for getting results from joint injections. Currently, joint injections are used to treat a variety of conditions, including osteoarthritis, synovitis, and osteochondrosis.
Patient selection and diagnosis are important before deciding if intra-articular (IA) injections are right for your horse. Your equine veterinarian should perform a complete lameness exam to determine exactly where your horse is sore. This exam may include a combination of flexions, diagnostic nerve and joint blocks, ultrasounds, and radiographs. Certain cases may even require MRI or diagnostic arthroscopy to identify the problem.
If your horse has a condition which your veterinarian thinks may be helped by injections, it is time to decide which drugs will be involved. Anti-inflammatories used in the joint include corticosteroids and hyaluronic acid. Corticosteroids are the most potent anti-inflammatories available for IA administration; they work by inhibiting prostaglandins which in turn decreases the number of inflammatory cells in the area. There are several types of steroid available for IA administration. Your veterinarian will choose which one to use based on the specific diagnosis, specific joint, and specific needs of the horse. It should be noted that there is some research that states that long term use of steroids in a healthy joint can lead to cartilage damage. This is why a specific diagnosis of joint disease is needed before beginning joint injections.
Hyaluronic acid is another important part of the joint care arsenal. HA is a component of normal, healthy synovial fluid and articular cartilage. It is important for lubrication of the joint as well as keeping inflammation out of the joint. In general, joint disease can lead to decreased production of HA in the joint. Hyaluronic acid can be injected directly into a diseased joint, or it can be injected intravenously (Legend). The IV formulation is thought to work on receptors located on the white blood cells (inflammatory cells).
Another potential component of the joint injection regime might include polysulfated glycosaminoglycans (trade name Adequan). PSGAG’s are the only disease-modifying product licensed by the FDA to treat equine osteoarthritis. This means that in addition to reducing pain and inflammation, PSGAG’s can actually inhibit cartilage degradation and stimulate cartilage repair. They can be administered intra-muscularly or directly into the joint.
Regenerative medicine products are another option for some cases. Products such as stem cells, protein-rich plasma (PRP), and Interleukin-1 receptor antagonist protein (IRAP) are all available to help mitigate some of the effects of joint disease.
One last product that will likely be injected (into the joint or intravenously) along with any of the treatments is a prophylactic dose of antibiotics. Although every measure is taken to create a sterile injection field, any time a needle enters the joint trauma is caused and a chance of bringing microbes with it exists. Good preparation, a sedated, well-controlled patient, and aseptic technique all contribute to the risk-management of joint injections. Putting a dose of antibiotics in the joint is just one more precaution to take to prevent infection.
As with any procedure, there are some risks. We have already discussed the use of antibiotics in the joint to help prevent infection. A joint flare is a sterile (non-infected) inflammatory reaction to the medications that have been injected. Most of those flares resolve with conservative therapy such as cold hosing, wrapping, and oral anti-inflammatories. Cellulitis (skin inflammation/infection) can happen if a small amount of medication leaks out from the joint under the skin.
Used appropriately, joint injections can help keep your horse sound and comfortable while doing his job.