Your shoulder is made up of three bones: your upper arm bone (humerus), your shoulder blade (scapula), and your collarbone (clavicle).
The head of your upper arm bone fits into a rounded socket in your shoulder blade. This socket is called the glenoid. A combination of muscles and tendons keeps your arm bone centered in your shoulder socket. These tissues are called the rotator cuff.
Cause of shoulder pain: bursitis, tendinitis, tendon tears, impingement, fracture etc
Physical Examination: a comprehensive examination will be required to find the causes of your shoulder pain. Your doctor will look for physical abnormalities, swelling, deformity or muscle weakness, and check for tender areas. He or she will observe your shoulder range of motion and strength.
Tests: your doctor may order specific tests to help identify the cause of your pain and any other problems: X-rays, magnetic resonance imaging (MRI) and ultrasound, computed tomography (CT) scan etc
Treatment generally involves rest, altering your activities, and physical therapy to help you improve shoulder strength and flexibility.