These injections are used to treat knee osteoarthritis. Hyaluronic acid is naturally found in your body as a part of healthy synovial fluid (the substance that lubricates joints). Injecting HA into the knees of patients with osteoarthritis is thought to help lubricate the joint, which reduces catching and grinding. Research suggests that HA injections may also help reduce inflammation. Treatment is often offered in a series of three to five injections one week apart, but some brands only require one injection.

There are 9 types of HA injections that have been FDA-approved to treat knee osteoarthritis in the United States: Hyalgan®, Supartz®, Orthovisc®, Monovisc®, GEL-SYN®, Synvisc(-One)®, Euflexxa®, Gel-One®, and GenVisc 850®. No HA product has been proven to work better than the others. However, each person is different and some patients respond better to a particular type of HA injection. Most insurance plans will cover one of the preceding HA treatments (single injection or multiple injections, depending on the brand) every six months.