3. Shoulder bursitis:
Bursitis is inflammation of the bursa sac, which is located at the bottom of your shoulder. It is a fluid-filled sac that protects the tendons, muscles, ligaments, and other joint structures that attach to your bones. It is also responsible for helping your arm move freely and cushions all the components of your shoulder joint to avoid rubbing bone against bone through the formation of synovial fluid.
Bursitis is a common cause of shoulder pain. The pain of bursitis is usually worse when you lift your arms overhead or carry things and is often relieved by putting your arm down and resting. If you have bursitis, you may also have a swollen area at the top of your shoulder where the shoulder blade and the acromion meet. This area is called the acromioclavicular joint.