[Magnetic resonance imaging of glenohumeral instability: new concepts]

The shoulder is the most unstable joint in the human body and is therefore susceptible not only to acute dislocations but also to minimal states of subluxation related to overuse. The latter condition is known as microinstability and is translated clinically into internal impingement syndromes. Both in dislocations due to acute traumatism and in microinstability, a series of injuries to the glenoid lip, glenohumeral capsule, the articular cartilage, the head of the humerus, the tendons of the rotator cuff, the long tendon of the biceps, the glenohumeral ligaments, and coracohumeral ligament can occur. Glenoid lip lesions are the most common and may present as isolated lesions or in combination with lesions of any of the other structures. These lesions most often affect the anteroinferior margin of the glenoids (the classic Bankard lesion), with different characteristics and variations on its location, (Bankard variants). Another predominant location of glenoid lip lesions is the superior margin (SLAP lesions). Magnetic resonance imaging (MRI), especially after intra-articular injection of contrast material, has shown great diagnostic accuracy in this type of lesions, although the interpretation of these images requires knowledge not only of the different lesions and combinations of lesions, but also of the normal variants that can easily be confused with these lesions.