Objective: As a minimal invasive surgery for the treatment of thumb carpometacarpal joint (trapeziometacarpal [TMC]) arthritis, we performed an arthroscopic synovectomy for Eaton stage II to IV arthritis.Patients and Methods: We included patients who were effectively treated with a corticosteroid injection, experienced recurrence of TMC pain, and had no major instability of the TMC. Surgery was performed in 17 female patients. Synovectomy was performed, when possible, using radiofrequency and a shaver. The mean follow-up period was 27.2 months.Results: Two patients required additional surgery; however, 15 patients were satisfied with the outcome. The mean visual analogue scale score improved from 8.8 preoperatively to 2.2 postoperatively.Conclusion: Arthroscopic synovectomy is indicated to be an effective treatment for stage II to IV TMC arthritis. The goal of this treatment was to relieve severe pain minimally invasively. Furthermore, if symptoms remain or reoccur, another curative procedure can be chosen.