Hyaluronan Injections for Osteoarthritis of the Knee
Editor's Note: This article was originally written by patient expert Matthew Thompson.
We've heard a lot recently about how the symptoms of knee osteoarthritis can be relieved by hyaluronan injections. The research we currently have shows that they do work, but like any treatment, the results can vary from person to person. In our clinic, I have seen a woman return to ballroom dancing after her knee pain decreased significantly, but I have also seen an entrepreneur who reported only a minimal improvement in his knee pain throughout his busy days. The results can vary.
Let's start with the simple facts about hyaluronan:
- Hyaluronan (also called hyaluronic acid) is a substance in normal joint fluid that lubricates the joint, much like oil lubricates engine components. The knee continuously produces its own hyaluronan.
- In osteoarthritis, there is a decrease in the amount of hyaluronan in the joint fluid. Also, the hyaluronan molecules break down, becoming less effective at lubricating the joint.
- The injections are thought to work by helping the knee normalize the hyaluronan in the joint fluid. The injections also may reduce inflammatory cells in the knee and reduce nerve impulses that cause pain.
- Hyaluronan injections are very safe. The chances of a significant adverse reaction (severe knee swelling, hypersensitivity reaction) are about 3 in 1000 based on the results of twenty research studies. This is much lower than the risk of gastrointestinal problems with taking anti-inflammatory medications.
- Hyaluronan injections do not work as well for people who are over age 65 or who have the most advanced stage of osteoarthritis (based on x-rays of the knee).
- There are 6 brands of hyaluronan typically used in the United States. There is currently not enough research to definitively prove that any one is better than the others. There are some subtle differences between them but it is too early to give them a definite ranking on how well they work. For those with egg/poultry allergies, you should know that all brands except Nuflexxa and Euflexxa are derived and purified in a laboratory from a rooster's comb, and there could be an increased risk of a hypersensitivity reaction to these injections.
- In the office, injections are given weekly for 3 to 5 weeks, depending on the brand and the discussion with your physician. If there is excess fluid in the knee, it may be drawn out before the injection is given.
- Some symptom relief typically is noticed after the 3rd or 4th week, and maximum benefit may not be reached until the 6th week or later. Relief of symptoms can last for 6 months or longer, but if symptoms return after 6 months, another round of injections can be given.
Learn more about different options available for the treatment of osteoarthritis.
Learn more about the basics of osteoarthritis, including symptoms, risk factors and causes.
Watch this video to learn more about Slowing Osteoarthritis of the Knee.
Wang, et al. Therapeutic Effects of Hyaluronic Acid on Osteoarthritis of the Knee; A Meta-Analysis of Randomized Controlled Trials. The Journal of Bone and Joint Surgery (American) 86:538-545 (2004)