I get Supartz injections in my right knee (they are spendy) - but seem to help. The first and second series helped more than the last series I had last fall. The first series was November 2006, second in about 2009, and the last series was in the fall of 2011. I think one is "allowed" to have the series twice a year. The packaging says to use a series of five injections - but "they" - "they" being Mayo personnel - generally only use a series of three injections given one week apart.
There are other brands of the stuff - but Supartz seems to be the one that Mayo uses more than the other ones.