According to World Health Organisation osteo-arthritis is the second commonest musculoskeletal problem in the world. Diacerein has been recently introduced in India for the treatment of osteo-arthritis. In view of the ulcerogenic potential of NSAIDs and the cardiotoxicity problems associated with COX-2 inhibitors, diacerein has the potential of being a non-ulcerogenic and non-cardiotoxic alternative respectively to NSAIDs and of COX-2 inhibitors in the treatment of osteo-arthritis. The present study was, therefore, undertaken to evaluate the efficacy and tolerability of diacerein in the treatment of osteo-arthritis. A total 7923 patients with osteo-arthritis of the knee fulfilling the selection criteria were enrolled in this open-label, multicentric postmarketing surveillance study. After a wash-out period of one week, patients were treated with 50mg diacerein tablets administered twice daily for 12 weeks. The primary efficacy variable of the present study was to assess the improvement in the visual analogue scale (VAS) scores for pain. The secondary variable was improvement in patients' and physicians' global assessment of efficacy of therapy. Results indicated that over the 12-week study period, diacerein 50mg tablets provided significant and sustained reduction the VAS pain scores. At baseline, VAS scores were 6.70 +/- 1.78. By the end of the 4th week, there was a significant reduction in the mean VAS scores by 21.8% and by the end of the study the mean VAS scores were further significantly reduced by 59.9%. As per the patients global assessment of treatment, 82.3% of the patients reported good to very good improvement at the end of 12 weeks therapy with diacerein. Similar responses were also recorded by the treating patients. Thus by the end of 12 weeks therapy, according to the physicians 85.5% of the total cases treated with diacerein were rated as having good to very good improvement. Therapy with diacerein was well tolerated and only 5.44% of the patients had an adverse event after treatment with diacerein. The most common adverse events were diarrhoea (2.3%), gastritis (0.99%), nausea (0.61%), abdominal pain or discomfort (0.44%) and vomiting (0.3%). The severity of the adverse events was mild in all the cases and disappeared with continued treatment. None of the patients dropped out of the study on account of adverse events or lack of efficacy. Thus, in conclusion, the results of the present study in a large population of Indian patients indicates that diacerein constitutes a novel approach to the treatment for the short- and long-term symptomatic management in Indian patients with osteo-arthritis of the knee.