The rotator cuff is the group of tendons that cap the head of the humerus, the arm bone, and hold it centred against the shoulder blade while the arm moves. Without the cuff, the deltoid would pull the head upwards instead of rotating the shoulder, and the arm would not lift.
It is a discreet structure that works extremely hard. It is involved in every everyday movement, on the most mobile joint in the human body, a joint that in return is held almost entirely by its muscles and tendons. That is why it wears out, and why it is behind the great majority of shoulder pain after forty.
Four rotator cuff muscles run from the shoulder blade and attach onto the head of the humerus. The long head of the biceps tendon crosses the same area and contributes to the stability of the whole. In my practice I therefore speak of five tendons, because that is what we see and what we repair in theatre.
It passes above the joint, under the acromion, and starts the lifting of the arm. It is the most exposed tendon and the first to tear, because it works in a narrow space where it rubs.
It sits at the back and provides external rotation, the movement of turning the hand away from the body with the elbow tucked in. It is what lets you turn a key or reach behind your head.
It lies flat against the front surface of the shoulder blade and provides internal rotation, the hand moving towards the stomach or behind the back. It is the counterweight to the infraspinatus, and a tear here unbalances the whole shoulder.
It completes external rotation, low down and at the back. Its condition matters a great deal when a reverse shoulder replacement is needed, because it is what allows usable rotation to be kept after surgery.
It crosses the joint before running down into the arm. It is often inflamed, sometimes dislocated out of its groove, and it is frequently the source of pain that is wrongly blamed on the rest of the cuff.
It does two things at once, and that is what makes it vulnerable. It stabilises, keeping the head of the humerus centred against the glenoid, a surface far smaller than the head itself. And it moves the arm, providing the rotations and starting the lift.
In practical terms, the rotator cuff is at work when you comb your hair, reach for something on a high shelf, fasten your seatbelt, carry a bag of shopping or turn round at the wheel. These are the very movements patients describe first when the cuff stops working.
In the great majority of cases nothing dramatic happens. The tendon wears down slowly, year after year, through rubbing under the acromion and through ageing of the tendon tissue itself. The tear is then the final stage of a long process, and many patients cannot recall any injury at all.
In younger patients a torn rotator cuff is most often traumatic: a fall onto an outstretched arm, a violent pulling movement, a shoulder dislocation. Here the pain is sudden and clearly dated, and how quickly it is treated matters more.
Three factors speed up the wear: repeated overhead movements, in certain jobs as much as in certain sports, smoking, which reduces the blood supply to the tendon, and the shape of the acromion, which in some people leaves less room for the supraspinatus.
Tendinitis, or tendinopathy, is inflammation of the tendon. It is painful, but the tendon itself is intact.
Calcific tendinitis is a deposit of crystals within the tendon, which causes the typical, often night-time, attacks of severe pain.
A tear, partial or full thickness, is the tendon coming away from the bone. It can be well tolerated for a long time.
Rotator cuff arthropathy is the late stage: the tendons have gone, the head of the humerus rides up and wears the joint. This is what is known as eccentric osteoarthritis of the shoulder.
Frozen shoulder, or adhesive capsulitis, is not a rotator cuff problem, but it often arises in the same context and can be mistaken for one early on.
Night pain is the most reliable sign. A shoulder that wakes you when you roll onto it, or that stops you sleeping on the affected side, deserves an opinion.
Rotator cuff pain on lifting the arm, between sixty and one hundred and twenty degrees, with the discomfort disappearing once the arm is fully raised, points to impingement under the acromion.
Loss of strength is more worrying than pain. An arm that drops when you try to hold it out horizontally, or a hand that can no longer be lifted away from the back, signals a large tear.
Finally, pain running down the arm as far as the elbow is common and unremarkable in rotator cuff problems. Pain that goes below the elbow, with pins and needles in the fingers, points instead to the neck.
The clinical examination remains the most important step. A series of simple tests, tendon by tendon, shows which one is affected before a single image is taken.
An X-ray does not show the tendons, but it shows what has become of them: the height of the humeral head under the acromion, the presence of a calcification, the state of the joint.
Ultrasound is quick, easy to obtain, and is often enough to confirm a tear. It depends heavily on the experience of the operator.
A rotator cuff MRI, or a CT arthrogram, is the reference investigation before any surgical decision. They show the size of the tear, how far the tendon has retracted and above all the quality of the muscle, which is the true prognostic factor.
Yes, very often. Many tears are found by chance in patients who have no complaints at all, and a tear does not in itself call for surgery. What decides is the pain, the loss of function, age, activity and the state of the muscle on imaging.
What you do need to know is that a torn tendon never reattaches on its own, and that the corresponding muscle gradually turns to fat. This degeneration cannot be reversed, and it is what closes the door on a repair if you wait too long. That is why I prefer to see a painful shoulder early, even if nothing is to be done straight away.
Four rotator muscles attach onto the head of the humerus: the supraspinatus, the infraspinatus, the subscapularis and the teres minor. The long head of the biceps tendon crosses the same area and contributes to the stability of the whole. In surgical practice we therefore speak of five tendons.
Over the point of the shoulder and the outer side of the arm, often as far as the elbow, rarely beyond. It is typically worse at night and disrupts sleep on the affected side. Pain running into the forearm with pins and needles in the fingers usually comes from the neck instead.
Ultrasound is often enough to confirm a tear. A rotator cuff MRI or a CT arthrogram is the reference investigation before any surgical decision, because only these show tendon retraction and the quality of the muscle. An X-ray remains useful for the joint itself.
No. A torn tendon never reattaches to the bone by itself. The pain can nonetheless settle and the shoulder become functional again without surgery, thanks to the remaining tendons and to physiotherapy. It is function we treat, not the image.
The supraspinatus starts the lifting of the arm, the infraspinatus and the teres minor provide external rotation, and the subscapularis provides internal rotation. All four run from the shoulder blade and converge on the head of the humerus, alongside the long head of the biceps tendon.
Three signs should prompt you to seek advice: pain that wakes you at night, difficulty lifting the arm between sixty and one hundred and twenty degrees, and above all loss of strength. The diagnosis is made on clinical examination and confirmed on imaging.
Yes. Smoking reduces the blood supply to the tendon, accelerates wear and lowers the chances of healing after a repair. It is the one risk factor a patient can act on directly before surgery.
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