What causes a frozen shoulder syndrome?
It is not known exactly what causes FSS. It can occur with or without an injury or trauma. Whatever the cause, it appears that the lining of the joint (the capsule) becomes inflamed, and scar tissue forms. This crowds the arm bone, which makes it difficult or impossible to move the shoulder. There is some evidence that poor posture can cause increase the risk of developing FSS. A long period of immobility, such as during an illness or accident may also be a factor in some cases. It is not thought that sleeping incorrectly can cause FSS, although some people do experience FSS like symptoms for a few minutes upon waking. .
