120 patients with knee osteoarthritis were randomized to a single intra-articular injection of either 40mg triamcinolone acetate, 3mg betamethasone disodium phosphate, 40mg methylprednisolone acetate or placebo. Patients were followed at 1, 3, 6, and 12 weeks after injection for pain reduction on a visual analog scale and functional improvement on the Lequesne Functional Index. Results demonstrated significantly greater pain reduction and functional improvement in each of the corticosteroid groups compared to the placebo group at 1, 3, 6, and 12-week follow-ups. The methylprednisolone group demonstrated significantly greater pain reduction to 3 weeks compared to betamethasone, and to 6 weeks compared to triamcinolone. No significant differences in functional improvement were observed between the corticosteroid groups.