Final answer:
Shoulder pain associated with scanning movements is often caused by repetitive strain, leading to conditions like bursitis, rotator cuff tears, and adhesive capsulitis. Referred pain can also cause discomfort in the shoulder from other internal issues.
Step-by-step explanation:
The main cause of shoulder pain associated with scanning movements, such as those performed during swimming or racquet sports, is often attributed to repetitive strain and overuse leading to conditions like bursitis, rotator cuff tears, or labral tears. In some cases, inflammation can also lead to adhesive capsulitis, commonly known as frozen shoulder, where scar tissue forms and reduces mobility. In instances where the arm is fully abducted and force is applied to the humerus, such as landing on an outstretched hand, dislocation or injury may result in acute pain and require medical attention. Damage to internal structures can also cause referred pain, where discomfort is felt in an area different from the actual site of the injury or irritation, such as shoulder pain stemming from diaphragm irritation.