Final answer:
Pain with external rotation of the shoulder is often related to issues with the rotator cuff muscles: supraspinatus, infraspinatus, teres minor, and subscapularis. These muscles form the rotator cuff and provide primary support and movement to the shoulder joint. Damage or inflammation to these muscles can cause pain and is common in activities that involve repetitive overhead motions.
Step-by-step explanation:
When experiencing pain with external rotation of the shoulder, it's often the rotator cuff muscles that are affected. These muscles include the supraspinatus, infraspinatus, teres minor, and subscapularis. These four muscles arise from the scapula and attach to the greater or lesser tubercles of the humerus. They provide primary support for the shoulder joint by encircling the head of the humerus and fusing to the articular capsule to form the rotator cuff. Pain during external rotation could suggest inflammation, impingement, or even a tear in these muscles, which are essential for maintaining the head of the humerus within the glenoid cavity and providing structural support for the glenohumeral joint.
These critical muscles also act as dynamic ligaments to constantly adjust their strength of contraction to resist forces acting on the shoulder. Particularly vulnerable during activities like baseball pitching or racquet sports, the rotator cuff can become inflamed or damaged due to the repetitive overhead motions required, leading to discomfort and reduced mobility.