Lateral subtalar joint (STJ) instability is an underrecognized contributor to persistent lateral hindfoot symptoms, especially among patients who continue to feel unstable after anatomically successful anterior talofibular ligament (ATFL) and calcaneofibular ligament (CFL) repair. Emerging cadaveric, biomechanical, and imaging work suggests a key stabilizing role for the lateral STJ capsule and the inferior extensor retinaculum (IER) complex. We provide a narrative review of the lateral STJ capsuloligamentous anatomy, relevant biomechanical data, and diagnostic considerations including MRI/ultrasound and dynamic fluoroscopic stress assessment. We then describe a practical operative approach for capsuloligamentous reinforcement of the lateral STJ using a flap of the medial band of the IER, with anchor fixation to the lateral talar process, and outline postoperative management. In the senior author’s experience, targeted subtalar capsuloligamentous repair can restore lateral stability in patients with isolated or residual STJ laxity after lateral ankle stabilization. The technique leverages local retinacular tissue to augment the lateral talocalcaneal ligament (LTCL) region and the lateral capsule while maintaining anatomic relationships. Lateral STJ capsuloligamentous laxity may drive persistent symptoms despite ATFL/CFL reconstruction. Surgeons should consider explicit subtalar assessment and, when indicated, capsular plication with IER augmentation. Prospective studies and standardized imaging/stress tests are needed to validate indications, outcomes, and durability

Keywords: Subtalar joint instability Lateral ankle instability

Allen Marque earned his Doctor of Podiatric Medicine (DPM) degree from Temple University. He subsequently completed five years of advanced training in foot and ankle surgery, including an internship at the University of Pennsylvania and a comprehensive foot and ankle surgical residency within the Thomas Jefferson University Health System. He further advanced his subspecialty training through a fellowship at the The University of Texas Health Science Center at San Antonio. Dr. Marque currently serves as the Fellowship Director of Sports Medicine in Foot and Ankle Surgery at Sports Medicine Associates of San Antonio.