 All patients selected will be included in the intention-to-treat group. Then, using blocked randomization method they will be assigned to receive either IAHA, or placebo saline solution. At both hospitals the study will consist of four injections of IAHA, 6 months apart, plus a 6 month period after the injection, resulting in a total follow-up period of 24 months. Before each new cycle a follow-up consultation will be performed in order to assess pain and function KOOS, quality of life SF-36, adverse events and consumption of acetaminophen and NSAIDS regarding the week before evaluation. X-rays will be performed in the beginning of follow-up, one year after that and 6 months after the last cycle of IAHA or placebo injections 24 months. 