Ankle sprains are mainly benign lesions, but if not well addressed can evolve into permanent disability. A non-treated lateral, syndesmotic or medial ankle instability can evolve into ankle osteoarthritis. For this reason, diagnosis and treatment of these entities is of extreme importance.In general, acute instabilities undergo conservative treatment, while chronic instabilities are better addressed with surgical treatment. It is important to identify which acute instabilities are better treated with early surgical treatment.Syndesmosis injuries are frequently overlooked and represent a cause for persistent pain in ankle sprains. Unstable syndesmotic lesions are always managed by surgery.Non-treated deltoid ligament ruptures can evolve into a progressive valgus deformity of the hindfoot, due to its links with the spring ligament complex. This concept would give new importance to the diagnosis and treatment of acute medial ligament lesions.Multi-ligament lesions are usually unstable and are better treated with early surgery. A high suspicion rate is required, especially for combined syndesmotic and medial lesions or lateral and medial lesions.Ankle arthroscopy is a powerful tool for both diagnostic and treatment purposes. It is becoming mandatory in the management of ankle instabilities and multiple arthroscopic lateral/syndesmotic/medial repair techniques are emerging. Cite this article: 2021;6:420-431. DOI: 10.1302/2058-5241.6.210017.