Intra-articular (IA) injection of medication is a common procedure in the management of joint disorders. In particular, the procedure is effective in the treatment of inflammatory conditions, with long acting corticosteroids most commonly used. These agents have been shown to reduce the signs and symptoms of inflammation, expressed primarily in the synovium of the joint, and are probably capable of slowing the progression of damage to joint cartilage and bone in some of these inflammatory conditions. Arthritis that is refractory to IA corticosteroid injections may respond to surgical, chemical, or, radioisotope synovectomy, procedures in which the inflamed synovial tissue is eradicated. It has been noted that infliximab, a monoclonal antibody directed to Tumor Necrosis Factor (TNF) - α, has high affinity for the TNF-α rich inflamed synovium. Recently, clinical benefit from IA injections of infliximab has been reported in some cases that were refractory to IA injections of corticosteroids. Similarly, the effectiveness of IA infliximab in suppression of joint inflammation has also been demonstrated in patients who could not receive systemic therapy with infliximab. These reports examined the effect of a single injection of infliximab100 mg injected into a large inflamed joint or 2 IA injections 24 hours apart.||We propose to further evaluate the use of IA infliximab in patients with intractable knee monoarthritis, explore the optimal mode of its employment, and assess the degree of infliximab systemic absorption from the IA injection. In a pilot study 40 knees will be evaluated, 20 injected with infliximab and 20 injected with a corticosteroid comparator reflecting the current standard of care.