Injections into synovial spaces (joint/bursa/sheath) are a common procedure in equine practice. These are usually performed for one of four main reasons:

1. In order to ‘block’ lameness: this is where local anaesthetic is injected into the joint to see if pain can be isolated tothis region.
2. The joint/sheath/bursa is being medicated. This is where a corticosteroid or other medication is injected into thejoint to treat lameness/inflammation/degeneration.
3. To get a sample of synovial fluid to check for infection. Sometimes an antibiotic and/or saline may be injected atthe same time.
4. To inject a liquid which shows up on x-rays to help diagnose certain conditions on x-ray.

The vet will do their best to perform this procedure in a controlled and clean way so as to reduce the risk of complication.

The main complication we worry about with synovial injections is the risk of taking bacteria in and causing an infection. This is extremely unlikely, but the risk exists no matter how careful the vet is. The published risk is 0.04% of synovial injections will result in infection. If your horse does get a synovial infection, they will need surgery in hospital to try and treat it. The practice will not bear the responsibility of the cost of this treatment as this is a recognised risk of this procedure.

Other risks of synovial injections include:

• An inflammatory reaction (joint ‘flare’) which can result in pain, heat and swelling. It can sometimes be difficult to ascertain if these are infected or not.
• There is a link between the use of corticosteroids and laminitis: this is very low risk but it does exist. Steroidinduced laminitis can be very serious and difficult to treat.
• There is a risk of further joint degeneration with synovial injections.

On rare occasions complications from synovial injections such as infection or laminitis can result in the horse requiring euthanasia on humane grounds.