Efficacy of low molecular weight intra-articular hyaluronic acid (LMW IA-HA,1.4X106 Dalton) and high molecular weight intraarticular hyaluronic acid (HMW IA-HA 6X106 Dalton) in knee osteoarthritis COMPARATIVE EFFICACY OF LOW- AND HIGHMOLECULAR WEIGHT INTRA-ARTICULAR HYALURONIC ACIDS IN PATIENTS WITH KNEE OSTEOARTHRITIS