Purpose: To evaluate the result of modified Br$ddot{o}$strom procedure with anchor suture and explore associate lesion under arthroscopy for chronic lateral instability. Materials and Methods: From May 2005 to March 2009, Retrospective analysis of 126 patients with chronic lateral instability who underwent modified Br$ddot{o}$strom procedure with anchor suture and arthroscopic procedure was done. Mean follow-up period was 13 months. Results: Chronic lateral instability of the ankle almost had local synovitis by arthroscopic examination. There were osteochondral lesion of talus on the anteromedial aspect in 63 cases, on the anterolateral aspect in 25 cases, osteochondral lesion of tibia side in 8 cases, fat hypertrophy of tibiofibular space in 120 cases, anterior fat impingement in 26 cases, intra-articular loose body in 13 cases. Mean Karlsson scoring scale was improve from 53 preoperatively to 91 postoperatively, There were 70 cases excellent, 27 cases good, 26 cases fair, 3 cases poor result according to the Sefton procedure. Conclusion: Modified Br$ddot{o}$strom procedure with anchor suture and arthroscopic procedure are reliable treatment method for chronic ankle lateral instability which has intraarticular pathology.