The main structures that ensure the stability of the elbow joint are lateral and medial collateral ligament complexes. The injury of some or all of these ligaments results in instability of the elbow. Collateral ligaments of the elbow joint are the specialized thickenings of the lateral and medial parts of the joint capsule. Medial collateral ligement complex consists of three bundles; anterior, posterior and transvers. The most important part of this complex is the anterior bundle. Posterior bundle is the thickening of the posterior side of the elbow capsule and best observed in 90 degrees flexion. The contribution of the transvers band (Cooper`s ligament) to the stability of the elbow is very low. The components of the lateral collateral ligament complex are less seperated from each other compared to the medial complex. Lateral collateral ligament complex consists of four sections: radial collateral ligament, annular ligament, lateral ulnar collateral ligament and accessory lateral collateral ligament. Elbow joint is one of the most harmonious and -stable joints of the musculo-skeletal system. This property is the result of the joint harmonious contribution of both soft tissues and joint surfaces. The dislocations or subluxations of the elbow typically occur as a result of falling on the abducted arm. While the body is turning inside over the elbow, arm turns outside over the body and a supination moment occurs in the elbow. Valgus and supination occuring together with flexion and axial compression is the mechanism resulting in posterolateral rotational subluxation and also can be clinically induced by lateral pivot shift test. Instability of the elbow is the tearing process of the ligaments around the elbow joint from lateral to medial due to a trauma induced by this type of mechanism.