A Closer Look at Knee Injections
The fluid in your knee joints have a natural lubricant between the bones called hyaluronic acid. The lubricant acts as a shock absorber. In many people, this lubricant wears away with time, causing knee pain. Your doctor may prescribe nonsteroidal anti-inflammatory drugs (NSAIDs) to provide relief. But if over-the-counter or prescription strength NSAIDs don’t provide relief, your doctor may recommend injections. Your options include synthetic hyaluronic acid and corticosteroids. Each acts in a different way.
Viscosupplementation injections infuse your problem joint with synthetic hyaluronic acid. Depending on the product your doctor uses, he or she may give you an injection once a week for three to five weeks. As part of the procedure, your doctor will likely remove a small amount of your own joint fluid to make room for the synthetic version. According to the American Academy of Orthopaedic Surgeons (AAOS), you are not likely to experience pain relief immediately. You may even have some swelling, pain, and a feeling of warmth at the site of your injection. Applying an ice pack will help, and your symptoms should go away quickly. For the first 48 hours, you should stay off your leg as much as possible and avoid heavy lifting.
At Your Appointment
What to Ask Your Doctor About Knee Arthritis
You should find that your pain lessens as you receive more injections. Hyaluronic acid is not an anti-inflammatory, but it may stimulate your body to make more of its own hyaluronic acid. It seems most helpful for those with early, mild-to-moderate knee conditions. Viscosupplementation is not recommended for people who have had osteoarthritis for a long time.
Sometimes doctors will inject corticosteroids into your knee joint to relieve pain. Cortisone is a specific kind of steroid that your adrenal glands make naturally. These glands are located above each kidney. Cortisone decreases inflammation and, in turn, reduces pain.
People with moderate-to-severe knee pain are likely candidates for corticosteroids. According to the AAOS, corticosteroid injections are most helpful if you have a lot of swelling. They are not as useful if your osteoarthritis affects your joint mechanics—your ability to move. Your doctor has a choice of corticosteroids to use.
As with viscosupplementation, the site of your injection can become inflamed immediately after the injection. Icing and avoiding strenuous activity can help with cortisone injections as well.
Manufacturers say that corticosteriods can provide relief from pain and inflammation, anywhere from a few days to more than six months. However, studies find the benefit is short-lived, from one to four weeks.
While cortisone injections don’t have the same side effects as oral steroids, they still have risks. If you get too many injections, your cartilage can break down, causing more joint damage. Cortisone injections can also lead to nerve damage. For this reason, your doctor is likely to limit the number of times you can have your knees injected. The AAOS recommends no more than four injections per joint per year.
Viscosupplementation Versus Cortisone Injections
Both approaches have mixed reviews. A 2009 analysis of studies on both types of injections revealed that people had better initial benefits from the cortisone injections than from viscosupplementation. After four weeks, the results were about the same. At the three- and six-month marks, however, relief was better from the hyaluronic acid (viscosupplementation).
Another analysis in 2012 offers a different viewpoint. It found that injections of hyaluronic acid have little effect on pain, and when they do, results start to fade after eight weeks. The study also suggested that the injections had side effects, including gastrointestinal and cardiovascular events. Doctors still don’t know the long-term effects of hyaluronic acid injections, and more research needs to be done in this area.
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- Rutjes AWS, et al. Viscosupplementation for Osteoarthritis of the Knee. A Systematic Review and Meta-analysis. Ann Intern Med. 2012;157(3):I-36.
- Arthritis of the Knee. American Academy of Orthopaedic Surgeons. http://orthoinfo.aaos.org/topic.cfm?topic=a00212
- Viscosupplementation Treatment for Knee Arthritis. American Academy of Orthopaedic Surgeons. http://orthoinfo.aaos.org/topic.cfm?topic=a00217
- Use of Corticosteroids in Osteoarthritis. Arthritis Foundation. http://www.arthritis.org/living-with-arthritis/treatments/medication/drug-types/corticosteroids/corticosteroid-injections.php
- Injections and Procedures for Knee Pain. Arthritis Foundation. http://www.arthritis.org/about-arthritis/where-it-hurts/knee-pain/treatment/knee-injection.php
- Hepper CT, et al. The Efficacy and Duration of Intra-articular Corticosteroid Injection for Knee Osteoarthritis: A Systematic Review of Level I Studies. J Am Acad Orthop Surg. 2009;17(10):638-46.
- Bannuru RR, et al. Therapeutic trajectory of hyaluronic acid versus corticosteroids in the treatment of knee osteoarthritis: a systematic review and meta-analysis. Arthritis Rheum. 2009;61(12):1704-11.