Frozen shoulder or adhesive capsulitis is a progressive inflammatory process that occurs at structures of the shoulder joint (glenohumeral joint) including the joint capsule and surrounding ligaments. This inflammatory process leads to characteristic swelling and stiffening of the joint capsule and ligaments which leads to pain and reduced mobility. The most common findings are synovial inflammation, capsular fibrosis (scarring), and thickening of structures (such as extra-capsular ligaments).