There is no accepted definition of frozen shoulder and there is no well-defined pathophysiological process. It may be due to scarring in the capsule surrounding the shoulder joint. Symptoms are pain and severe restriction of active and passive movement. Frozen shoulder affects 2% of adults, usually in the 40-60 years age group. In 20% it subsequently develops in the other shoulder. It is described as having 3 phases:
- Initial phase is the development of pain over 2-9 months. Pain is worse at night.
- Pain subsides over the subsequent 4-12 months but stiffness and restriction of movement persist.
- The third phase lasts 5-24 months and during this time pain and stiffness resolve. The course can, however, take much longer and even when symptoms have resolved there can be some limitation in movement.