Frozen shoulder is a painful, persistent stiffness of the shoulder joint. Movements of the shoulder become reduced, sometimes completely 'frozen'. It is thought to be due to scar-like tissue forming in the shoulder capsule. Scar tissue may form for a number of reasons, such as after a minor shoulder injury or from heavy exercise, but sometimes there is no obvious cause.

Frozen shoulder affects about 1 in 50 adults at some stage in their life. It most commonly occurs in people aged between 40 and 60. It is more common in people who have diabetes.

Symptoms
The typical symptoms are pain, stiffness, and limitation in the range of movement of the shoulder. The symptoms typically have three phases.

• Phase one - the 'freezing', painful phase. This typically lasts 2-9 months. The first symptom is usually pain. Stiffness and limitation in movement then also gradually build up. The pain is typically worse at night, and when lying on the affected side.
• Phase two - the 'frozen', stiff phase. This typically lasts 4-12 months. Pain gradually eases but stiffness and limitation in movement remain and can get worse. All movements of the shoulder are affected but the movement most severely affected is usually rotation of the arm outwards. The muscles around the shoulder may waste as they are not used.
• Phase three - the 'thawing', recovery phase. This typically lasts 5-24 months. The stiffness gradually goes and movement gradually returns to normal.