Ankle sprains are the most common injuries in sports and recreational activities. Ankle osteoarthritis can be caused by ankle ligament lesions. Latency time between injury and osteoarthritis is influenced by the type and side of the injured ligaments. The side of the ligamentous lesion correlates with the hindfoot alignment. Case series; Level of evidence, 4. Of a cohort of 247 patients with ankle arthritis, we reviewed data from 30 patients (33 ankles; mean age, 58.6 years) with ligamentous end-stage ankle osteoarthritis. The patients were evaluated etiologically, clinically, and radiologically. Etiologic analysis: 55% had a ligamentous lesion from sports injuries (soccer, 33%); 85% injured the lateral ankle ligaments, and 15% injured the medial and medial-lateral ligaments. The mean latency time between injury and osteoarthritis was 34.3 years. The survivorship rate for single severe ankle sprains was worse than that for chronic recurrent ligamentous lesions (mean latency time, 25.7 vs 38.0 years; P < .05), and the rate for medial sprains was worse than for lateral sprains (mean latency time, 27.5 vs 35.0 years; P < .05). At follow-up, the American Orthopaedic Foot and Ankle Society hindfoot score was 23.0 points, 52% had varus malalignment, 52% had persistent instability, and the mean ankle arthritis grade was 2.6 points. There was a correlation between chronic lateral ankle instability and varus malalignment. Lateral ankle sprains in sports are the main cause of ligamentous posttraumatic ankle osteoarthritis and correlate with varus malalignment. At the time of end-stage ligamentous ankle osteoarthritis, persistent instability may be encountered.