The study population will include 50 patients with bilateral knee osteoarthritis, admitted for their first knee replacement surgery. Only patients with older than 50 years with primary osteoarthritis will be included. The patients will be randomized into 2 groups. Intervention group will receive an injection of 2ml Diprospan diluted in 10 ml Bupivocaine. The control group will receive an injection of 10ml of Bupivocaine. All patients will be followed after 6 weeks and three functional rehabilitation and pain scores will be assessed (VAS pain score, Timed Up and Go Score and Functional Ambulatory Category Scale).