Final answer:
The painful condition described is subacromial impingement or rotator cuff tendinitis, which is caused by the entrapment of soft tissues and tendons between the humerus and acromion, often as a result of repetitive shoulder activities or injury.
Step-by-step explanation:
A painful condition occurring when the tendons and soft tissues around the shoulder joint become trapped between the humerus and the acromion is known as subacromial impingement or rotator cuff tendinitis. Shoulder injuries are frequent, especially with repetitive use of the upper limb in activities like throwing, swimming, or racquet sports. Such actions can lead to acute or chronic bursitis, a tear of the glenoid labrum, or rotator cuff injuries.
The rotator cuff, consisting of the tendons of the deep subscapularis, supraspinatus, infraspinatus, and teres minor, can become pinched and inflamed, and may tear from the repetitive overhead motion. Moreover, direct trauma to the shoulder may result in an acromioclavicular joint injury or 'shoulder separation'. All these conditions lead to pain and decreased mobility, with the possibility of developing scar tissue and experiencing a reduction in shoulder mobility, known as adhesive capsulitis or 'frozen shoulder'.