Methods: A prospective controlled randomized double blind studied with three groups (n = 35 each group) of patients with symptomatic osteoarthritis of the knees receive intra-articular medication in a single moment will be undertaken. The three groups will be: Botulinum toxin type A Group: patients who receive 100 units of botulinum toxin; hexacetonide of triamcinolone Group: patients who receive 40mg of triamcinolone hexacetonide, and saline group: patients who receive 2ml of normal saline. Patients will be assessed by evaluators " blind " in 4 times during 12 weeks of follow-up with clinical assessment instruments (pain, quality of life questionnaire as short form 36 questionnaire) , functional ( WOMAC questionnaire) , and ultrasound (quantitative and semi quantitative measure of synovial hypertrophy and semi quantitative Power Doppler ) .The following statistical tests will be used : Student's t test, Mann - Whitney , chi- square test and ANOVA for repeated measures . Will be considered as statistical significance the difference of 5 %.