Ulnohumeral arthroplasty is commonly used to treat mild or moderate osteoarthritis (OA) of the elbow. Previous studies have reported good to excellent results, but have not focused on the continuing degenerative process which can alter the outcome. The authors retrospectively evaluated 10 patients with elbow OA who were treated with the Outerbridge-Kashiwagi procedure from 2004 to 2006. The mean increase in the overall Andrews and Carson scores was 91 points (range : 70 to 100) at 3 months follow-up. The overall gain in range of motion, patient satisfaction rate and VAS and Andrews and Carson scores was found to be significantly diminished at the last follow-up, as compared with early postoperative values. Although ulnohumeral arthroplasty is an accepted procedure for elbow osteoarthritis, the deterioration of the overall gain in pronation/supination and progression of the disease can affect the final scores and patient satisfaction.