The shoulder joint is a complex assembly of muscles and tendons, subject to enormous pressure but capable of the most intricate movement. Those of us involved in sports with lots of repetitive arm movements, especially over the head, may find shoulder pain common as we get older. This may be caused by a rotator cuff injury
The website rotator cuff injury.co.uk gives help and advice on identifying if you do have a rotator cuff injury, and if so what kind of injury it is. If it seems likely that you do have a rotator cuff injury there is information on treatment, both medical and self-help.
Always seek medical advice if you have pain that lasts more than 2 or 3 days and does not respond to traditional pain-killers.