Pain in the right upper arm is a common clinical phenomenon. If the pain persists without relief or becomes more and more severe, it may be caused by some serious diseases, such as breast cancer and lung cancer, etc. Right upper arm pain may occur, but this is relatively rare. The most common cause of right upper arm pain is frozen shoulder, osteoarthritis, cervical spondylosis, etc. After the cause is clearly identified and actively treated, the symptoms will gradually improve. 1. Frozen shoulder: also known as adhesive capsulitis, this is an inflammatory adhesion and stiffness of the shoulder glenohumeral capsule caused by various reasons, characterized by pain around the shoulder joint and limited movement in all directions. Frozen shoulder on the right side can lead to adhesions and contractures at the starting point of the right upper arm muscles, thus causing pain in the right upper arm. 2. Osteoarthritis: It is a chronic arthritic disease characterized by degenerative joint cartilage and secondary osteophytes. When the joint capsule undergoes fibrous degeneration and thickening, which restricts joint movement, the muscles around the joint will develop protective spasm, which in turn manifests pain in the right upper arm; 3. Cervical spondylosis: It is a syndrome of cervical disc degeneration and secondary changes that stimulate or compress the adjacent spinal cord, nerves, blood vessels and other tissues, and a series of symptoms and signs appear. The early clinical manifestation is neck and shoulder pain, which can radiate to the right upper arm when the pain intensifies. 4. Rotator cuff injury: The common site is anterior shoulder pain, located in front of the deltoid muscle and laterally. In the acute stage, the pain is severe and persistent; in the chronic stage, it is spontaneous dull pain. The symptoms are aggravated after shoulder activity or after increasing the load. Passive external rotation of the shoulder joint will also aggravate the pain, and the aggravation of symptoms at night is one of the common clinical manifestations. The pressure pain is mostly seen in the proximal side of the greater tuberosity of the humerus, or the subacromial space area. 5. Local fracture: If the right upper arm is hit by external force, it may lead to a fracture of the right upper arm, resulting in pain.