The causes of pain in the upper part of the left shoulder joint mainly include diseases of the shoulder joint itself and diseases of internal organs. 1. Diseases of the shoulder joint itself: such as prolonged strain of muscles and ligaments, rotator cuff injury, shoulder fracture, dislocation, subacromial impingement sign and so on, all of which may cause pain in the upper part of the left shoulder joint. Secondly, female patients around 50 years old need to be alert to the presence of frozen shoulder. In addition, if the patient has cervical spondylosis, the pain in the upper part of the left shoulder joint may also occur, which is clinically known as cervical-shoulder syndrome. 2. Visceral diseases: angina, pleurisy, pancreatitis and even lung tumors can also cause shoulder pain. Diseases of internal organs often can not be precisely localized, but there will be limb reflexes, because visceral pain directly stimulate the spinal cord surface sensory neurons, causing pain in the corresponding surface area, and into the same spinal cord segment uploading, the emergence of radiating pain. Patients with pain in the upper part of the left shoulder joint should be alerted, and it is recommended to consult a specialized medical institution to clarify the cause and treat the original disease.