The shoulder is a complex, highly mobile joint designed to provide the highest amount of motion of any joint in the body. It is a ball and socket joint surrounded by a variety of ligaments, tendons, and muscles that are responsible for moving the arm. Frozen shoulder, or adhesive capsulitis, is a condition in which the capsule of the shoulder joint becomes more rigid an inflamed. This causes severe limits in the range of motion and pain when trying to move the shoulder joint.
We are not entirely sure why frozen shoulder happens to certain people, but something triggers the connective tissue and capsule around the shoulder joint to thicken and get inflamed, tightening the shoulder joint
Frozen shoulder usually develops slowly and in three stages, each lasting for several weeks to months if untreated.