Frozen shoulder: past, present, and future.

Frozen shoulder is a condition characterised by pain and global restriction of movement with loss of external rotation. It can be divided into primary and secondary forms. In the primary form there is no associated disease or a history of trauma, whilst the secondary form occurs after trauma or surgery. Its incidence in Caucasian populations is estimated to be between 2 and 5%. It occurs mainly in persons aged 40 to 60 years; women are more commonly affected than men. Clinically it can be divided into a painful phase, a stiff phase, and a recovery phase. The painful phase lasts 2 to 9 months and usually begins insidiously. The pain interferes with sleep and is increased by movement, the patient becoming more aware of limitation of movement as time passes. In the stiff phase (typically lasting 3 to 12 months) restriction of movement becomes a major problem, which facilitates diagnosis. The recovery phase follows, during which the patient regains movement and function over a period of 5 to 26 months. The total duration of disability therefore lasts 12 to 42 months (30 months on average). 1 Some patients may be left with some restriction of movement, but in most there is no residual impairment. Recurrence in the same shoulder has never been reported, though up to 20% of affected persons develop the condition on the opposite side. 2 The natural history of frozen shoulder is important not only for reassuring the patient that the condition will eventually improve, but also for assessing the results of various treatments. Although its aetiology is still unknown, frozen shoulder is associated with several diseases. For instance, diabetic patients have a higher incidence than the general population, 3 as do those with hyperthyroidism,