So far there is no convincing evidence that any treatment can be really effective in slowing or preventing the development of OA. The viscosupplementation by intraarticular injection of hyaluronate-derived products has gained popularity as a treatment modality of gonarthrosis. Today there are various papers on the treatment of gonarthrosis by intraarticular injection. Several methods have shown good results. There isn't, however, a consensus on the best method. The investigators know that in the treatment of osteoarthritis, with the viscosupplementation Hylan is superior in the long term, than the infiltration with cortisone. The good short term results achieved by infiltration of cortisone make us think about the combination of these drugs. The investigators will be assessing 104 patients with osteoarthritis of the knee, divided into two groups. Patients in group 1 will be subjected to infiltration procedure 6ml of Hylan. Patients in Group 2 will undergo the procedure of infiltration with 6ml of Hylan and 1ml (20mg) of hexacetonide Triamcinolone. The researcher will apply the informed consent term, the pain visual analog scale (VAS), WOMAC and Lequesne questionnaires. The questionnaires will be answered before infiltration (week zero), one week after the puncture (week 1), four weeks after (week 4) and 12 weeks after (week 12) and 24 weeks after (week 24).