Frozen shoulder is still not very understood yet. What is known is that frozen shoulder causes pain in the shoulder joint that is caused by a restriction of motion, but medical professionals are still trying to find out the cause behind this restricted motion. It is also known as adhesive capsulitis because the capsule around the shoulder joint contracts almost permanently, causing scar tissue to build around the joint.

Many times a cause for the pain in the shoulder joint from frozen shoulder is unknown. It can be caused by a traumatic injury or decided by age and gender. For example, it is more likely to occur in women ages 40-60 than in men in the same age range. Those affected with frozen shoulder may also have a history of shoulder pain or of pain in shoulder joints of family members.