Elbow instability is common and may occur after a variety of injuries, including falls or direct blows. Instability can be classified as either acute or chronic. Acute instability is classified as simple (without fracture) or complex (with associated fracture). Chronic instability is classified as a chronically dislocated or recurrently unstable elbow. Recurrent instability commonly presents as isolated medial or lateral collateral ligament insufficiency. A chronically dislocated elbow is often more complex, involving both osseous and ligamentous injuries. The treatment of simple dislocations typically involves closed reduction and nonsurgical management. Chronic recurrent lateral and medial collateral ligament insufficiencies have very different clinical characteristics, but definitive treatment frequently involves ligament reconstruction. Complex instability usually requires surgery, which includes open reduction and internal fixation of coronoid and olecranon fractures, repair or replacement of radial head fractures, and lateral collateral ligament repair. Medial collateral ligament repair and/or external fixation are rarely required to restore stability. It is important for surgeons to understand current concepts in the diagnosis and management of acute and chronic elbow instability as well as the preferred surgical treatments and techniques for the management of these injuries.