The causes of painful shoulder are multiple.
We can systematize them in two ways: structural or functional and intra-articular or extra-articular.
Starting at the end, we can locate pain around the shoulder from problems that occur within the joint between the humerus and shoulder blade, such as cartilage lesions surrounding the humeral head and the glenoid cavity in the shoulder blade; capsule injuries and ligaments surrounding it; lesions of the long portion of the biceps (LBP) that has an initially intraarticular course; or inflammation / rupture of the set of tendons that cause the shoulder to move (rotator cuff – supraspinatus, infraspinatus, subscapularis).
The most common pathologies, extra-articular to the glenohumeral joint, are inflammation of the sub acromial pouch, which covers the rotator cuff (bursitis); the narrowing of the space where these tendons move (conflict syndrome); the inflammation or arthrosis of the joint that exists between the collarbone and the tip of the shoulder blade (acromion).
There are also diseases whose pain is referred to the shoulder but which do not originate in the shoulder. This may be the case with diseases of the cervical spine, inflammation of the set of nerves that emerge from the cervical spine; Some pathologies originating in the lungs and even the heart, such as acute myocardial infarction, may give localized pain in the shoulder.
But all these situations have a structural translation of the cause of pain.
However, certain circumstances give pain but have no associated structural changes. These are the case of functional changes, where pain arises from an imbalance in the harmony of functioning of anatomical structures. These are more difficult to diagnose and in which complementary diagnostic tests give us little information, being the fundamental medical examination for the diagnosis.