98 patients with knee osteoarthritis were randomized in a 2x2 factorial design to receive treatment with either joint lavage plus intra-articular (IA) corticosteroid injection, joint lavage plus IA placebo injection, IA corticosteroid injection alone, or IA placebo injection alone. Patients were followed-up for pain, function, and patient global assessment at 1, 4, 12, and 24 weeks. No significant interaction was observed by the combination of joint lavage and IA corticosteroid injection. Within-group changes for pain demonstrated significant reduction with IA corticosteroid injection at 1 and 4 weeks, while significant reduction with joint lavage was observed at 4, 12, and 24 weeks.