### What you need to know A 45 year old woman falls on ice and injures her shoulder. Assessment at her local hospital reveals bruising only and no bony injury on plain radiographs. Despite ongoing reassurance and participation in a physiotherapy programme for three months, she continues to complain of pain, weakness, and inability to raise her arm. Eventually she is referred to a specialist shoulder clinic, where an ultrasound scan confirms she has suffered an acute full thickness tear of her supraspinatus tendon. Failing to identify an acute full thickness rotator cuff tear is a common problem, and this article is aimed at raising awareness of the condition and its correct management. The article is directed to all clinicians, but especially emergency department clinicians, trauma clinic clinicians, and general practitioners, who tend to see such cases. The rotator cuff comprises four important muscles (supraspinatus, infraspinatus, teres minor, and subscapularis) which attach close to the humeral head via tendons and are critically involved in stability and function of the shoulder. A rotator cuff tear is when one or more of these tendons tears or detaches from the humerus (fig 1). These tears can vary in size and be acute or chronic. Chronic full and partial thickness tears are due to tendon degeneration and attrition, and these patients …