To assess reliability, hand function tests were measured twice without local treatment of the MCP in 25 patients with rheumatoid arthritis (RA). The discriminative capacity of the hand function tests with respect to the results of intra-articular corticosteroid injection was assessed in 28 RA patients with synovitis of an MCP joint. Thereafter, a randomized, observer-blind treatment study was performed in 21 RA patients with synovitis of an MCP joint; 10 of the patients were treated. Results/Conclusions. This study showed that the efficacy of treatment of an MCP joint can be measured by several reliable and discriminative parameters: passive flexion, the Ritchie pain score, swelling, the Arthritis Impact Measurements Scales question about buttoning clothes, and visual analogue scale questions about the activity of the disease and swelling of the joint.