Frozen Shoulder Anatomy Frozen shoulder, or adhesive capsulitis, is a condition that affects the shoulder joint, causing pain and stiffness. The shoulder is a ball-and-socket joint, consisting of: 1. Humerus (arm bone): The "ball" of the joint. 2. Scapula (shoulder blade): The "socket" of the joint, called the glenoid. 3. Joint capsule: A connective tissue structure surrounding the shoulder joint that allows movement. In frozen shoulder, this capsule becomes thickened and tight, restricting the