Inclusion Criteria:
1. Patients aged between 40 and 65 years who diagnosed with primary OA knee (medial tibiofemoral compartment) according to ACR criteria
2. Grade II-III OA severity that classified by the Kellgren-Lawrence classification
3. Varus malalignment ≤ 15°
4. Body mass index (BMI) ≤ 30 kg/m2
5. Pain on walking at 15 metres ≥ 30 mm using 100 mm visual analogue pain score (VAPS)
6. Evidence of adequate contraceptive methods in women of childbearing age
Exclusion Criteria:
1. Accompanying osteoarthritis of the hip of sufficient severity to interfere with the functional assessment of the knee
2. Intra-articular treatment with any product (corticosteroids in the last 3 months, glycosaminoglycans, hyaluronic acid in the last 6 months, etc.), joint lavage or arthroscopic procedures within 6 months before the start of the study
3. Oral corticosteroids, oral symptomatic slow acting drug for OA (SYSADOA) treatment (chondroitin sulfate, glucosamine sulfate, piascledin, diacerein) within last 3 months
4. Current treatment with anti-depressants, tranquilisers, antacids or antibiotics
5. Poor general health or other conditions which would make regular hospital attendance difficult
6. Primary inflammatory painful conditions of the knee (e.g. rheumatoid arthritis, psoriatic arthropathy, pseudo-gout)
7. Painful knee conditions other than osteoarthritis (e.g. Sudeck's atrophy, intra-articular neoplasm, villonodular synovitis)
8. Evolving arthritis requiring surgery within the coming year;
9. Persistent diarrhoea (\> 3 stools /24 h) or laxative use (any laxative use is to be stopped before inclusion in the trial)
10. Severe gastrointestinal disorders, indications or history of severe gastrointestinal disorders (e.g. gastric or duodenal ulcers, ulcerative colitis, Crohn's syndrome, diverticulitis, recurrent pancreatitis)
11. Renal insufficiency (estimate glomerular filtration rate ≤ 60 ml/min/1.73 m2)
12. Hepatic disease (transaminases \> 2.5 x upper limit of normal values (ULN) or total bilirubin \> 2 x ULN) or history of alcoholism and liver disease
13. Severe parenchymal organ disease
14. History of heart attack or stroke, or have had serious diseases of the heart such as congestive heart failure, or taking clopidogrel.
15. Patient with diabetes mellitus (DM) who has heamoglobin A1c level \> 8%
16. Patient with hypertension who has systolic blood pressure \> 150 mmHg or diastolic Blood pressure \> 95 mmHg
17. Pregnancy or lactation
18. Participation in a drug clinical trial within the 3 months before the start of the study;
19. Ascertained hypersensitivity to the active ingredient diacerein, to similar compounds, to the excipients or to paracetamol, naproxen, and omeprazole
20. Contraindications for magnetic resonance imaging (MRI) assessment such as heart pacemaker, aneurysm clip or claustrophobia
21. Knee size measured at lower thigh \> 50 cm
