Abstract
1. The "frozen" shoulder syndrome is due to an inflammatory lesion in the musculotendinous cuff invoked by a local area of degeneration.
2. The available evidence suggests that the primary site of the degenerative lesion is in the supraspinatus tendon.
3. Other causes of shoulder pain which must be differentiated from "frozen" shoulder are peritendinitis of the long head of biceps, degeneration or tears of the supraspinatus, and calcified deposits in the supraspinatus.
4. An explanation of the pathogenesis of lesions of the musculo-tendinous cuff is submitted in which the different types of clinico-pathological syndrome are correlated. This hypothesis is in accord with the experimental, clinical and operative findings.