Viscosupplementation by intra-articular injection of hyaluronate products has recently gained popularity as a treatment modality of gonarthritis. Hyaluronic Acid is responsible for the elasticity and viscosity of the synovial fluid, protecting the joint. Biopsy studies show that besides the gain in pain and function, viscosupplementation may lead to structural changes of the cartilage. Currently there are several studies on the effect of intra-articular injection of hyaluronic acid in gonarthritis. There is not, however, a consensus on the best method. Regarding the substance to be injected, corticosteroids alone exhibit rapid results, but poor durability. Viscosupplementation shows more consistent results. However, especially when using derivatives with higher molecular weight hyaluronan, there is a significant number of patients that present an acute synovial reaction to viscosupplementation specially in the first cycle of three injections. The association triamcinolone injection with hyaluronic acid decreases the complaints in the first month of treatment. Our objective is to evaluate what is the best dosage of viscosupplementation with hyaluronic acid (OSTEONIL®) associated with 1 ml (20 mg) of triamcinolone hexacetonide by comparing two groups of patients with knee OA, the first with a single application of 3 ampoules and second with three applications, one per week for three weeks. One hundred and four knee osteoarthritis (KOA) patients, which are currently in usual care for KOA at the Osteometabolic Group - Department of Orthopedics and Traumatology - University of São Paulo General Hospital - will be assessed. After signing the informed consent, participants will respond WOMAC™, Lequesne™, VAS, SF-36 (quality of life) and subjective IKDC (International Knee Documentation Committee). The questionnaires and functional assessment will be performed before the procedure infiltration with 1month, 3 months, 6 months and 1 year of intervention.Twenty Patients will be submitted to evaluation using force platform and balance NeuroCom ®, with the following tests: weight support during the squat (weight bearing squat (WBS), one-leg support (unilateral stance (U.S.), from sitting to foot (sit to stand - STS). Previously, at 1 month, 3 month, 6 month and 12 months after the intervention.

Frontal weight-bearing, profile and axial radiographs will be performed to radiologically assess participants' knees.Patients will be randomly divided into two groups of 54 patients, (groups 1 and 2). Patients in group 1 (G1) will be submitted to viscosupplementation with 1 application of 3 vials of hyaluronic acid 20mg/2ml (OSTEONIL®) and 1 ml (20 mg) triamcinolone, whereas group 2 patients will be submitted to viscosupplementation with three applications of one ampoule of hyaluronic acid 20 mg/2ml (one per week for three weeks), with the first application of OSTEONIL® with 1 ml (20 mg) triamcinolone.

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