As with any medical issue, a shoulder problem is generally diagnosed using a three-part process;
Medical history – the patient tells the doctor about any injury or other condition that might be causing the pain. Time line of the shoulder pain. Exacerbating and remitting factors...How does the pain get worse? How does the pain get better? This will give many clues to the physician about what might be causing this.
Keep in mind the differential diagnosis for shoulder pain is long. Many different things can cause it. The second part of the process is physical examination. The doctor examines the patient to feel for injury and discover the limits of movement, location of pain, extent of joint instability. Many times this will be enough and medical history and physical exams do a very accurate diagnosis about what exactly is going on with the shoulder. If the doctor still has more questions, the doctor may order more imaging tests to help make a specific diagnosis.
A standard x-ray in which low level radiation is passed through the body to produce a picture called a radiograph. This type of x-ray is useful for diagnosing fractures or other problems with the bones. Soft tissue such as muscles and tendons do not show up on x-rays. Ultrasound is a different non-evasive technique in which ultrasound waves can be used to visualize some structures in the shoulder particularly the ones closer to the surface. Many times the problems with the rotator cuff are due to some of the structures located close to the surface and therefore is very helpful in making this diagnosis.
Finally, a frequently used imaging technique is the magnetic residence imaging (MRI) which is another non-evasive procedure in which a machine with a strong magnet passes a force through the body to produce a series of cross-sectional images of the shoulder. This allows the doctor to look at the soft tissues and help make a more definitive diagnosis. Most certainly before a surgery is proposed, an MRI will likely be available for the doctor to review to plan surgery.