Abstract Background For lateral ankle ligament rupture, surgical repair has been considered for patients requiring return to high-demanding sports. However, there is a lack of systematic research regarding arthroscopic treatment followed by ligament repair for severe acute ankle sprain. The purpose of this study was to analyze the mid-term outcomes of arthroscopy followed by open anatomic lateral ankle ligament repair surgery for acute lateral ankle sprain and the impact of ligament rupture site on the outcomes. Methods Professional or amateur athletes with clinically- and radiologically-confirmed grade III acute lateral ankle ligament injuries undergoing ankle arthroscopy followed by open anatomic ligament repair between June 2007 and May 2017 were reviewed. Intra-articular lesions and the location of rupture were first examined under arthroscopy. Simple suture repair was performed for mid- substance ligament rupture (middle group), while suture repair with anchors were used for the ruptures near the ligament attachment site on the fibular (proximal group), talar or the calcaneal side (distal group). Outcomes were evaluated at final follow-up, including visual analog scale (VAS) pain score, American Orthopaedic Foot & Ankle Society (AOFAS) score, Tegner score, time to return to sports, resumption of pre-injury sports level, sprain recurrence and range of motion (ROM). Results A total of 117 patients were included for analysis, with a mean follow-up duration of 46.4 ± 16.1 months. There were 48 (41%) cases in the proximal group, 41 (35%) cases in the middle group and 28 (24%) cases in the distal group respectively. At final follow-up, all of the VAS score, AOFAS score and the Tegner score were significantly improved from the pre-operative level (p