An open, randomized study to investigate the plasma and synovial fluid concentrations of glucosamine before and after repeated doses of crystalline glucosamine sulfate administered as oral soluble powder formulation presented as a sachet (1500 mg o.a.d.) and to assess the efficacy of glucosamine vs pure analgesic (paracetamol 1000 mg t.i.d.) in patients with knee osteoarthritis.

INTERVENTION: Trade Name: DONA*OS 20BUST 1500MG Pharmaceutical Form: Oral powder INN or Proposed INN: Glucosamine Concentration unit: mg milligram(s) Concentration type: equal Concentration number: 1500‐ Trade Name: TACHIPIRINA*30CPR 500MG Pharmaceutical Form: Tablet INN or Proposed INN: Paracetamol Concentration unit: mg milligram(s) Concentration type: equal Concentration number: 500‐ CONDITION: Joint disorders ; MedDRA version: 9.1 Level: LLT Classification code 10048794 Term: Gonarthrosis PRIMARY OUTCOME: Main Objective: To assess the plasma and synovial fluid concentrations of glucosamine before and after multiple oral doses of crystalline glucosamine sulfate administered as an oral soluble powder presented as sachet. To assess the efficacy and safety of glucosamine sulfate, in continuous treatment for 6 months, on osteoarthritis of the knee symptoms in comparison with paraceamol. Primary end point(s): To assess glucosamine concentrations in plasma and synovial fluid determined at baseline and after 1, 6 and after 12 months, in patients not responding after 6 month of treatment with glucosamine sulfate. Secondary Objective: INCLUSION CRITERIA: 1.Male and female Caucasian, out‐patients with a diagnosis of primary knee osteoarthritis, aged 45‐75 years. 2.The diagnosis of knee osteoarthritis will be based on the clinical classification criteria developed by ACR; knee pain and at least one of the three clinical findings: Age >50 years; morning stiffness <30 minutes duration; crepitus on active motion. 3.Lequesne index at the randomization visit of at least 4 points. 4. Apart for knee osteoarthritis, good general health, as determined at the screening examination by medical history and physical examination. 5. Able to understand and willing to sign the Informed Consent Form. Are the trial subjects under 18? no Number of subjects for this age range: F.1.2 Adults (18‐64 years) yes F.1.2.1 Number of subjects for this age range F.1.3 Elderly (>=65 years) yes F.1.3.1 Number of subjects for this age range