Joint injections are a common method of treating arthritis, especially in the early stages. Typically this injection contains a local anaesthetic to numb the inside of the joint, and a steroid which acts like an anti-inflammatory drug. Sometimes the injection is done as a test to confirm that the pain is coming from the affected joint, rather than other causes such as the back.
Other options include injections of hyaluronic acid, also known as viscosupplementation. Unfortunately these have not been shown to offer any improvement over standard steroid injections, and as a result these are no longer recommended.
Knee injections are routinely performed in the outpatient clinic. Hip injections require the use of an X-ray machine to ensure that the injection is delivered into the hip joint; these therefore need to be done in the operating theatre. They are usually done under a local anaesthetic; occasionally a brief general anaesthetic is needed.
Injections should last a few months, and if successful, can be repeated as often as needed. If the injection gives less than 3 months’ improvement, then it is unlikely that further injections will be beneficial and more definitive treatment may be indicated.
The risks of joint injection are very small, but include bleeding from the injection site. The risk of introducing an infection into the joint is extremely small. However joint replacement within 3 months of a steroid injection is associated with increased infection, so I would advise that you wait at least 3 months between injection and definitive surgery.