Subacromial impingement Subacromial impingement is defined as “mechanical irritation of the rotator cuff resulting from direct contact with the anterior border of the rostral arch” and is one of the most common causes of shoulder pain in the middle-aged and elderly, far exceeding the traditional term “frozen shoulder”. In this case, the shoulder pain originates from the subacromial space. Clinical manifestations and diagnosis 1. Pain usually occurs during abduction, touch, lifting, and throwing; 2. Neer’s sign is positive, and compression of the rotator cuff and subacromial bursa reproduces impingement symptoms. 6. Supraspinatus exit x-ray may reveal bony redundancy in the anterior external angle of the rotator cuff or hooked rotator cuff or ligamentous hypertrophy; 7. If rotator cuff injury is suspected, further MRI is required. Treatment Conservative treatment may include oral NSAIDs, physiotherapy, ice, cryotherapy, and subacromial local closure to reduce pain and inflammation. If conservative treatment is ineffective for more than 6 months, arthroscopic surgery including subacromial bursa cleaning and acromioplasty can be considered when the pain seriously affects life and work.