Dr. Matthew Thompson on this site wrote about Euflexxa and other hyaluronic acid inhections here. (Click the blue text to read it)

In general, your doctor gives you injections once a week for 3 to five weeks, depening on which hyaluronic acid you use and what you and your doctor decide. You many not notice any relief until after the 3rd or 4th week. You may not feel maxomum benefit until after six weeks. If the symptoms return after six months, you can repeat the course of injections.

So, generally, you wouldn't have more than 10 injections in a year.

Talk to your doctor if you are considering the injections or if you have tried them and they haven't been helping. Work with your doctor to find the best treatment for you.