What is multidirectional instability of the shoulder?
Multidirectional instability (MDI) is a common shoulder problem seen in young athletes who specialize in overhead movements in their sports. It is a diagnosis specific to the glenohumeral joint of the shoulder and refers to a general laxity of the glenohumeral joint capsule. In a healthy shoulder, the head of the humerus is stabilized within the glenoid fossa (glenohumeral joint) through multiple structures including (from the inside out) the labrum, glenohumeral ligaments, joint capsule, and rotator cuff muscles. If there is damage or weakness in any of the stabilizing structures, the integrity of the glenohumeral joint can be compromised. The purpose of the stabilizing structures is to keep the head of the humerus safely within the boundaries of the glenoid fossa while the arm is in motion. In a healthy joint, the connective tissue structures (labrum, ligament, joint capsule) work to restrict the movement of the head of the humerus while the rotator cuff muscles contract to safely ke
