Rotator cuff

Function | Symptoms | Diagnosis | Treatment methods | Follow-up | Consultation

The rotator cuff of the shoulder is a unique and very interesting structure. This is necessary because no other joint in the body is as mobile as the shoulder. This articulation is owing to the fact that the glenoid cavity is very small and flat and so provides very little grip for the head of the humerus. The rotator cuff consists of four muscles and their tendons. The tendons act to transmit the force of the muscles to the bones. The muscles are all attached to the scapula and pass over the shoulder joint to the head of the humerus. They surround the head of the humerus on three sides (anterior, posterior and superior): this resembled an open shirt sleeve to the earlier anatomists. Hence the term "cuff".


The subscapularis muscle is the anterior muscle of the rotator cuff and its biggest. It covers the entire anterior surface of the scapula, i.e. it lies between the shoulder blade and the ribs. It tapers towards the head of the humerus where its upper portions become tendinous, the lower third remains muscular. The tendon inserts into the head of the humerus on the lesser tuberosity. Although it is a large and powerful muscle, it only has a small range of motion. It acts to rotate the arm inwards. Other large and powerful muscles assist in this. However, if you want to place your hand on your back, such as when taking a wallet from the back pocket or pulling up your trousers, this requires the subscapularis. The muscle is innervated by the superior and inferior subscapular nerves.

The supraspinatus muscle is the uppermost muscle of the rotator cuff. It arises from the supraspinous fossa, a groove located above the spine, the bony ridge running across the back of the scapula. Its tendon needs to pass through the very narrow space beneath the acromion. The tendon then passes to the head of the humerus and finally inserts on the greater tuberosity. The muscle is very important for the mobility of the shoulder as it supports raising the arm laterally (abduction). As it does so, it ensures that the deltoid muscle does not draw the head of the humerus upwards within the joint where it can clamp underneath the acromion (impingement). The head of the humerus is therefore held within the joint so that it executes a rotation and can raise the arm. However, it is the supraspinatus tendon itself that is often pinched under the acromion and causes pain. The muscle is innervated by the suprascapular nerve, which needs to traverse a narrow passage before it reaches the muscle.

The infraspinatus muscle is the posterior, upper muscle of the rotator cuff and takes up the entire space on the posterior scapula beneath its spine. It tapers towards the head of the humerus and its tendon inserts slightly behind that of the supraspinatus on the upper, posterior portion of the greater tuberosity. The tendon fibres partially cross with those of supraspinatus at the insertion site. It is the external rotator, which means it is responsible for rotating the arm outwards. It is innervated by the same nerve as the supraspinatus; this nerve needs to pass through another narrow space on its route.

The teres minor muscle is so called because it is round and the smallest muscle of the rotator cuff. It runs from the lower external edge of the scapula to the lower portion of the greater tuberosity. Together with the infraspinatus muscle, it is the only external rotator in the shoulder joint. This function is enormously important as it allows us to raise the hand in front of the face. The muscle is innervated by branches of the axillary nerve, which also innervates the large, important deltoid muscle.

The deltoid muscle is not a part of the rotator cuff, but is the most important muscle at the shoulder joint for moving the arm. It is a large and powerful muscle that gives the shoulder its round shape. Its course resembles that of an epaulette: it arises on the external clavicle and acromion and passes to the humerus where it inserts slightly above half-way on the exterior side. When we raise the arm laterally, we can feel and see the action of the deltoid muscle very clearly. It is controlled by the axillary nerve, which is therefore a very important nerve for the shoulder.

Owing to its anatomy, the pull of the muscle at the start of the movement when the arm is hanging at the side of the body is directly upwards. However, this cannot rotate the joint as the lever is absent. It requires the rotator cuff for this.

There are still other muscles involved in moving the arm. However, they are not required for understanding the function of the rotator cuff.

The task of the rotator cuff is dynamic stabilisation of the head of the humerus within the joint. This means that an external force, or the pull of different muscles on the humerus does not lead to the dislocation of the head of the humerus from the joint. This risk arises because the glenoid cavity of the shoulder is flat and small and cannot surround the head of the humerus, unlike the hip joint. The shoulder joint resembles a golf ball on the tee (its socket) but placed horizontally, not vertically.

The anterior muscle (subscapularis) and the two posterior muscles (infraspinatus and teres minor) loop around the head of the humerus like a bridle around the head of a horse. This way they can exert different forces that work dynamically forwards and backwards. As a major exception to this, the two posterior muscles are also involved in the actual movement of the arm during external rotation.

Enabling movement

The uppermost muscle, supraspinatus, requires an understanding of the traction vectors of the supraspinatus and deltoid muscles. These are at right angles to each other: the deltoid vector is vertical and the supraspinatus vector is horizontal. This means that the deltoid pulls the humerus directly upwards. As this upward pull has no lever and therefore no torque, the head of the humerus would glide upwards out of the joint until it struck the acromion painfully. This is prevented by the horizontal pull of supraspinatus. As the muscle passes over the head of the humerus and presses inwards on the joint, it not only holds the head tight within the joint and prevents it gliding upwards, but also guides lateral lifting of the arm away from the body (abduction). It therefore acts like a lever to help the deltoid to abduct the arm with force.


Tendons act to transmit the force of a muscle to the bone. To do this they need to withstand superhuman forces as the forces are generally large and the levers small. During the crawling movement of the arm, the force on the subscapularis can be up to 1,725 N. When we hold up a 25-kg weight with an outstretched arm, the force required from the deltoid is around 12,400 N. As tendons cannot be stretched, it is these that tear and rarely the muscles. And, because they need to withstand great stresses within a small space, they do not have their own blood supply. This means that they regenerate slowly and are more susceptible to degradation.

Tendons either tear owing to an accident, such as a fall onto the shoulder, or as a consequence of degradation. There are two reasons for degradation in turn. This can happen owing to overexertion, e.g. throwing sports, tennis, etc., or through the ageing of the tendon (degenerative). A tendon can tear partially or completely. If it is only partially torn, it may be that it is not torn through the entire thickness of the tendon. The tendons of the rotator cuff are arranged in sheets (like a bed). It may also be that the innermost sheet (relative to the joint cavity) has a tear, but the sheets above this are intact (called a PASTA lesion). More rarely, the uppermost sheet tears and the deeper sheets remain intact. It may also be that the tendon has torn at all layers, but not across the entire width of its insertion. This is similar to tearing halfway through a notebook.

A degenerative tear usually occurs in the elderly, often those who previously stressed their joints. However, as the rotator cuff serves to guide the head of the humerus within the joint, a tear can eventually lead to inappropriate stress within the joint and to the head of the humerus moving upwards. This will inevitably lead to degradation of the entire joint over time, to osteoarthritis. Which symptoms have which causes must be investigated clearly in these cases. Does the pain come from the joint or the tear in the tendon? Is the movement impaired owing to the rotator cuff or the degradation of the joint cartilage? Are other factors involved such as rheumatoid arthritis or neck problems? Is the patient discomforted by the pain or the loss of function or both? All these questions (and more) must be investigated carefully in order to establish a therapy personalised for the patient.


The two most important symptoms of a torn tendon are pain and loss of function, i.e. the inability to move the arm. The severity of these symptoms is strongly dependent on the type and cause of the tear and on the person who has the tear.

Naturally, traumatic ruptures cause immediate pain. Depending on the extent of the tear, these can immediately be very strong then decrease, or they can be less strong but present for a longer time. As the pain often improves significantly after a few days, the patients often do not consult a doctor. Highly typical for an accident is that the arm can barely be moved directly afterwards (pseudoparesis). However, this can also improve over time. In any event, the strength in the arm is reduced.

If the rotator cuff is injured in an accident, a significant loss of strength or function usually follows. There are patients who this does not disturb and who can live with this as they tend not to use their arm much anyway. However, this is not the case for most patients. They need to be able to use their arm again fully for work or sport. Depending on the type and size of the tear, an attempt can be made with physiotherapy. You should not wait too long for success, though. A torn tendon retracts and its muscle atrophies and accumulates fat. Eventually so much so that the tendon can no longer be sutured. In most cases, your specialist will suggest surgery. Not only to correct the shoulder, but to maintain it for the future. This is because a torn tendon can eventually no longer be sutured back together.

Tears from overexertion frequently affect athletes and physically active people. This is not only those who work above their head, but also occupations such as hairdressers, chefs, dentists or teachers, etc. Often they are not that young, but their work places high demands on their shoulder joint. The supraspinatus tendon is most commonly affected. This is because it must pass under the very narrow acromion and can chafe there. Furthermore, it nearly makes a right angle at its origin every time the arm is raised. This leads to chafing within the tendon, and therefore to small fibre tears. Similar to when your socks wear through. This tends to occur when we age because the tissues become more brittle. With regard to the joints, we start to age at 40. Often the tendon is only partially torn. The function is usually largely retained, but it is very painful. One rule of thumb assumes that a tear smaller than 50% of the tendon diameter can heal. Expansion of the tear is to be expected.


It is important to consult a specialist. Your GP (or emergency doctor) is your first contact person. However, further diagnosis should not be delayed, especially in an accident. The specialist will question you closely about your symptoms, e.g. the accident itself, pain when belting up, dressing, working over your head or at night. They will then examine you and test the mobility and strength in the joint. The doctor often already has a provisional diagnosis by this stage. This is then confirmed with an X-ray and often MRI. Ultrasound is also used occasionally.


Apart from pain relievers and physiotherapy, an injection of cortisone into the joint can also be used for pain therapy. This should be used sparingly, though, as cortisone does not aid healing of the tendon. However, the side effects of the cortisone are negligible for a single injection. Approximately half of all people with a tear owing to degradation have become accustomed to this and have learned how to live well with the aid of physiotherapy. The other half remains symptomatic. These are frequently those with high demands on their joint. When the non-surgical methods have been exhausted and the symptoms still persist, it is time to discuss surgery. Depending on the condition of the patient overall and of their joint in particular, different surgeries will be suggested.

For tears of the rotator cuff, the anterior subscapularis muscle, has a special role. This is because it acts as the anterior border of the shoulder joint and is therefore particularly important for holding the head of the humerus within the joint. If it tears, this border is removed and the head of the humerus can dislocate forwards out of the joint when raising the arm (subluxation). This blocks the movement and is very painful. There is little risk of subluxation of the head of the humerus for a small lesion at the top of the tendon (Grade I according to Lafosse), but for an advanced tear. The extremely methodical Dr Lafosse classifies such a tear as Grade V, which describes subluxation. This would not be so bad if the torn tendon could be replaced with another. Unfortunately, such replacement surgery (tendon transfer) is indeed simply a replacement and not sufficient for satisfactory function. However, a further surgical technique is currently under development whereby the tendon of the latissimus dorsi muscle is moved and may one day be able to deliver better results. If there is an injury to the subscapularis muscle, it may be that your specialist will push for an operation even for a small injury so as to prevent severe consequences in the future.


Most shoulder operations today are performed with keyhole surgery, or arthroscopy. This modern technique has several advantages, primarily indeed that the joint does not need to be opened and the injuries from the operation are therefore much smaller. Instead of a large incision, depending on the surgery a series of small incisions are made that are difficult to see afterwards. The operation is then performed with a camera and special instruments. Such an operation is not stressful for the body and it recovers very quickly. However, the shoulder can sometimes hurt and swell up. A catheter can be put in place for the pain and the swelling recedes by itself after a few days. Immobilisation, which was previously nearly always provided, is only used today in most cases immediately after the operation to protect the shoulder. You can usually leave the hospital after 3–5 days, without the immobilisation.

However, there must be healing after the operation, otherwise it is of little benefit. The arm should therefore usually not be used for 6 weeks. During this time there is physiotherapy where you learn to move the arm passively. This is enormously important as otherwise the joint becomes stiff. After 6 weeks, you can then begin to move the joint itself then build up strength and mobility together with the physiotherapy. This always takes a long time. The recovery time after shoulder surgery is often 6 months or longer.


Good health is the most important thing. This includes sufficient movement, healthy eating and trying to live as stress-free as possible, despite a shoulder problem. Physiotherapy is often prescribed even before the surgery so that the joints remain mobile and the muscles active. The exercises should be done at home every day. For larger procedures it may be useful to take dietary supplements (vitamins and proteins) that help to strengthen the immune system around the time of the operation. These can have a positive effect on the risk of infection. However, the risk of infection is very low for arthroscopies. Smoking should be avoided whenever possible. It impairs perfusion and therefore healing. Before each operation, your GP will give you a check-up to rule out any nasty surprises. After the operation it is very important to follow the doctor’s instructions. In the healing phase especially you need rest, but not inactivity. You will be taught daily exercises. These are the key to recovery. Better 5 minutes per day than 15 minutes every 3 days.


The costs of such an operation depend on various factors, such as the duration and complexity of the procedure and the length of the hospitalisation. Health insurance usually reimburses all costs if you have the appropriate insurance coverage. For the Pyramid Clinic you will require private or semi-private supplementary insurance.

If you wish to finance the operation yourself, we will provide you with a quote on request following a comprehensive examination. This also applies especially to patients from abroad.


Our doctors have many years of experience and are highly skilled in sports and joint surgery. We guarantee rapid, expert assessment and consultation and treatment in line with the latest medical findings. Don’t hesitate to get in touch if you would like a second opinion.

Please note that we are a private clinic and that you will need additional insurance (semi-private/private) in case of hospitalization, or will have to pay eventual treatment costs yourself. If you have any questions, please contact us.