Neck and shoulder pain can be directly related. The nerves that come through the neck extend into the shoulder and down the arm. One to diagnose them would take x-rays of the neck area and including the shoulder to make sure that there is not a shoulder injury as well. The shoulder joint is a ball and socket joint, and since it allows so much motion it's more susceptible to injury. The length of the arm is also a long lever so anything that occurs below the elbow can cause more force on the shoulder, such as dislocation or if there's a fall you can fracture your clavicle or fracture your arm, theses would all be diagnosed by x-ray and by a physician checking your shoulder. The neck also needs to be checked many times because if there's a fall it can affect the neck and the shoulder as well. This would be diagnosed by MRI scan, a CAT scan, or x-rays.