If the shoulder joint feels swollen, the first thing to consider is whether there is inflammation in the bursa or synovial membrane of the shoulder joint. Once the bursa or synovial membrane of the shoulder joint becomes inflamed, there will be a slight exudation inside the shoulder joint, which will lead to an increase in pressure inside the shoulder joint capsule, resulting in a swollen feeling. This symptom may also be caused by cervical spine diseases, such as cervical disc herniation or cervical spondylosis, which may compress the cervical nerve and cause swelling in the shoulder joint in the nerve distribution area.