Shoulder instability can be due to a single, acute traumatic event, generalized joint laxity, or repeated episodes of microtrauma. The later occurs in the throwing athlete. The most common lesion involving the labrum is the anterior inferior labral tear, associated with capsuloperiosteal stripping (classic Bankart lesion). A number of variants of the Bankart lesion have been described recently and include the ALPSA lesion, SLAP lesion, and HAGHL lesion, among others. Lesions of the long head of the biceps tendon can be seen in isolation (tears, tendinosis, dislocation) or in association with rotator cuff and labral lesions. Conventional MR and MR arthrography have been extensively used for the preoperative diagnosis of these lesions, with reportedly good accuracy. An understanding of the normal anatomy and biomechanics of the shoulder joint is essential for proper interpretation of the MRI manifestations of these conditions.