Shoulder periarthritis, also known as frozen shoulder and shoulder coagulation, is also known as “fifty shoulder” because it occurs at the age of about 50. Primary frozen shoulder, also known as idiopathic frozen shoulder, has not been found to have a clear cause. Secondary frozen shoulder refers to shoulder pain and joint stiffness secondary to trauma or surgery on the affected upper extremity. It is important to distinguish between primary and secondary frozen shoulder in order to choose the right treatment. The diagnosis of primary frozen shoulder is based on: 1. no clear history of trauma or surgical treatment to the shoulder; 2. limited movement of the shoulder joint in all directions at the time of examination; 3. normal joint space and no abnormalities around the joint (such as bone spurs) on X-ray plain radiographs. The diagnosis of secondary frozen shoulder is based on: 1. A clear history of trauma, low energy trauma, or surgery in and around the joint area; 2. Restricted movement of the shoulder joint in one direction, multiple directions, or all directions at the time of examination; 3. Normal joint space on X-ray plain film.