Pain between the shoulders can be caused by rheumatoid arthritis, according to WebMD. A specific type of rheumatoid arthritis known as ankylosing spondylitis is commonly accompanied by pain between the shoulders.
Ankylosing spondylitis is a type of rheumatoid arthritis that affects approximately 0.1 to 0.5 percent of the adult population, reports WebMD. It is characterized by pain from the top to the bottom of the spine, including between the shoulder blades. Additionally, it may also cause pain in the lower back and buttocks. The pain generally increases at rest and decreases with activity. The condition generally affects young men, especially those younger than 30.