Injections are used to help in the management of osteoarthritis, but they are not a cure for the condition. They act by reducing symptoms such s pain and discomfort with the aim of improving function once more. As with other medicines, they should be used as a package, for example, alongside exercising or physiotherapy. The injections that we will cover in this article are called intra-articular injections – injections directly into the joint itself. They are therefore very different to the usual intramuscular injections (e.g. the flu jab) or subcutaneous injections (e.g. those used to administer insulin). There are two intra-articular injections commonly used in the management of osteoarthritis:
- Corticosteroid injections
- Hyaluronic acid
We will discuss these two injections and look at how effective they are, who they are suitable for, and potential side effects.
Corticosteroid intra-articular injections
Corticosteroids are hormones that are either produced naturally by the adrenal gland (found above the kidney) or produced synthetically. Most injection preparations are synthetic. They have various metabolic functions, but are used in osteoarthritis because of their potent ability to reduce inflammation. They were first used in the 1950s and to date most studies have concentrated on the knee joint, although there are some indications that it may also be beneficial for the hips. The vast majority of the research conducted with the knee joints confirms that corticosteroid injections are beneficial when compared to a placebo treatment. Today approximately 53% of doctors use these injections to help alleviate pain caused by osteoarthritis.
As mentioned earlier, the corticosteroid injection is not a cure for osteoarthritis but it can help relieve the pain and inflammation. The onset of pain reduction is usually rapid (between 24-48 hours) with the maximum effect being reached within a few days. Studies have shown that the benefits last up to 4 weeks in most subjects and up to 3 months in some patients who have effusions of the knee. They can be repeated up to four times per year for the knee joint although usually less often for hand joints. Research to date has not shown repeated injections to cause any deterioration of osteoarthritis in humans.
It is not uncommon following the injection to have a temporary, mild flare-up of knee pain occasionally accompanied by some inflammation. This is due to a natural reaction of the synovial fluid in the joint to the crystal steroid solution of the injection. It is usually an immediate side effect but it is not permanent, and the treatment for this is a cold compress.
Hyaluronic acid is a naturally occurring component of the synovial fluid and is also found in the cartilage. It is highly viscous and acts as a shock absorber within the joint. It also stores energy that can be released when there is rapid joint movement and acts as a lubricant when there is slower movement. It is thought it has a role in maintaining a healthy cartilage. In the osteoarthritic joint there is less naturally occurring hyalronic acid and it can be less viscous.
By injecting hyaluronic acid directly into the joint the depleted levels are replenished and hence ease the pain and improve function of the joint.
Hyaluronic acid injections are not a cure for osteoarthritis,but they are used to help reduce the symptoms (pain, swelling, stiffness). The benefits are usually noticed between 2 to 5 weeks, although this can vary. The benefits usually last about 6 months.