Four muscles form the rotator cuff: supraspinatus, infraspinatus, teres minor and subscapularis. They run from your shoulder blade to the top of your arm bone. Supraspinatus lifts the arm out to the side and is the most commonly injured. Infraspinatus and teres minor rotate the arm outwards, and subscapularis rotates it inwards. Your physiotherapist tests each one separately.

A torn tendon does not usually knit back together on its own, but many people regain full function without surgery. The surrounding cuff muscles and shoulder blade muscles can be trained to take over the work, which reduces pain and restores strength. Surgery is more often considered for younger people with a traumatic tear, or when a well-run rehabilitation program has not restored the function you need.

A partial tear involves some fibres of the tendon while the rest remain attached. A full-thickness tear goes all the way through, so the tendon no longer pulls on the bone at that point. Full-thickness tears are more likely to cause obvious weakness. Both types can be painful, and pain level is a poor guide to tear size.

Yes. Rotator cuff pain is commonly felt over the outside of the upper arm, roughly where a shirt sleeve ends, rather than in the joint itself. It rarely travels past the elbow. Pain that runs into the forearm and hand, or comes with pins and needles and numbness, more often points to the neck, and your physiotherapist will screen for this.

Not usually. Prolonged sling use lets the shoulder stiffen and the cuff muscles waste, which makes rehabilitation harder. A sling is sometimes used briefly after a traumatic injury or surgery, on specific advice. For most rotator cuff injuries you are better off using the arm within a comfortable range and avoid the positions that provoke sharp pain.

Yes. Tendon tissue becomes less elastic and slower to repair with age, so cuff tears become more common from your forties onwards. Many older adults have tendon changes on imaging with no pain at all. That is why treatment focuses on your strength, movement and symptoms rather than on scan findings alone.