Arthritis
This is also a significant cause of shoulder pain, and there are different types of arthritis. They all have in common inflammation as one of the main mechanisms. Your own immune system can trigger this inflammation in rheumatoid arthritis or by wear and tear in the case of osteoarthritis. They usually feature progressive symptoms, but we can also have arthritis after an articulation infection, which has a rapid onset. It is often associated with swelling and stiffness of the joint.