Answered by, Amy Poulin-Braim, VMD, DACVS-LA, Neshanic Station, NJ
Questions: How real is the chance injections cause infection? Answer: You ask a very important question regarding joint injections.
Current literature suggests that the incidence of infection post joint injection is extremely low as long as the appropriate precautions are taken prior to injection.
Your veterinarian likely has a very strict protocol for joint injections to do as much as possible to mitigate this risk. This may include: injecting your horse in a clean, quiet environment with the barn doors closed to reduce air turbulence and possible dirt contamination of the injection site. Aseptic preparation of the injection site with a surgical scrub and alcohol wipe down. Use of sterile gloves, needles and syringes with a new bottle of medication and antibiotic used in the joint. Applying a sterile wrap over the site post injection. Reduced exercise and bathing/hosing for a few days post injection and a gradual reintroduction to exercise under saddle.
If joint infection were to occur, generally speaking it is most common to see clinical signs of non-weight bearing lameness, heat, pain and swelling associated with the joint within 3-5 days post injection. However, it has been seen as far out at 14 days.
Joint injections certainly have their place in helping our horse’s comfort level when an appropriate and complete lameness examination has been performed and other diagnostics (nerve blocks, radiographs, ultrasound, nuclear scintigraphy, MRI, CT etc.) are used to determine the specific site of pain causing the lameness. Injections should be used when needed, and not prophylactically as ‘routine maintenance’, as this could be detrimental to the joint cartilage if injected without a need into a normal joint.
Anytime a needle enters into a synovial space, there is always that slight risk of flare (inflammation without infection) or infection. So the fewer times the synovial space is entered with a needle, the less chance there is of that occurrence. Thank you very much again & good luck!
Question: Why do some horses experience laminitis after joint injections?
Answer: To date, there have been no definitive published research studies establishing a connection or cause and effect between joint injections and laminitis in the veterinary literature.
That being said, there may be certain horses that veterinarians may be more wary of injecting corticosteroids. Those would include horses with a previous history of laminitis and those horses that are obese and/or have been diagnosed with insulin resistance or Equine Metabolic Syndrome. Corticosteroids are potent anti-inflammatory and analgesic (pain relieving) drugs and may affect certain metabolic pathways depending on type of steroid and dose used.
While joint injections are very helpful to those horses where the lameness has been localized to a certain area and there is concurrent intra-articular arthritis or synovitis (inflammation of the joint capsule), it is not an innocuous procedure and could be detrimental to a normal healthy joint with no indication of inflammation. There is always a risk, albeit low, of joint flare or infection post injection even when all appropriate steps to aseptic preparation and post injection care are instituted. Therefore, joint injections should be carefully considered and risk analysis performed by your veterinarian. Generally speaking, the universal rule of thumb is that the lowest level/dose of corticosteroid should be injected that will elicit a response regardless of horse age, breed, use or history.
If your horse is considered to be in the possible higher risk categories described above, alternatives to corticosteroids for joint injections could also be considered if joint injections are considered to be necessary. That could included: platelet rich plasma, IRAP, mesenchymal stem cells, Legend or Adequan. It is always best to have your veterinarian evaluate your horse for lameness and identify the source of lameness with appropriate diagnostic tests prior to just simply injecting a joint based on a hunch. Your veterinarian will take into consideration the age, breed, use and prior history coming up with a plan for an appropriate injection protocol. They can explain to you the pros and cons of each option.