We developed a simple 5 point scale, the Joint Alignment and Motion (JAM) Scale, to estimate joint deformity in patients with rheumatoid arthritis (RA). The scale is based on an estimate of the percent of normal range of motion and joint alignment and requires 5 min to perform when added to a typical joint count. This deformity measure has good interobserver reliability (r = 0.72) and appears stable over time. The JAM score measures joint characteristics distinct from tenderness and swelling and correlates strongly with functional measures (walk time, grip strength and self-reported functional status). Joint deformity should be considered when interpreting functional measures for patients with RA.