The term "rotator cuff" refers to a group of four tendons that attach four shoulder muscles to the upper arm. Tendons are stringy tissues that attach muscle to bone. (The 4 tendons are the supraspinatus, infraspinatus, subscapularis and teres minor tendons)
A tear of the rotator cuff can occur to any one of these 4 tendons. Most commonly it is the supraspinatus tendon that tears.
Injuries to the rotator cuff are probably the commonest of shoulder problems.
A healthy shoulder is the most versatile joint in the human body. It has a wider range of motion, able to more freely, and in more directions, than any other joint. The shoulder's versatility enables us to retrieve soup cans from the cupboard, to hammer nails, swing golf clubs, roll bowling balls, and perform thousands of other activities.
The shoulder's flexibility is due to its unique structure. Like the hip, the shoulder is a "ball-and-socket" joint - a "ball" at the top of the upper arm bone (the humerus) fits neatly into a "socket" formed by the shoulder blade (scapula).
But unlike the hip joint, where the ball sits in a deep, well-protected socket, the shoulder socket is very shallow. So the soft tissues surrounding the shoulder are most important in maintaining the stability of the shoulder. The rotator cuff tendons help to stabilize the shoulder joint and turn the arm outward and inward.
The rotator cuff tendons are particularly susceptible to wear and tear over time, and hence susceptible to injury, due to the way the rotator cuff tendons pass across the shoulder to the upper arm (see below).
Most rotator cuff problems therefore develop over time. Over a period of years, the rotator cuff can become
Why does the rotator cuff tear?
It is easy to appreciate why the rotator cuff is liable to tear
Ordinarily, the rotator cuff tendons move freely in the space between the top of the upper arm and a part of the shoulder blade known as the acromion, which overhangs the rotator cuff. The space is an arch (formed by the acromion bone, the coracoid bone and the ligament connecting these bones, the coracoacromial ligament). But in some people, this space may be inadequate to allow the normal smooth gliding movements of the rotator cuff as it moves the arm. This may be simply due to the different shape of the acromion (more slopy than normal and so lessening the space ), or due to degenerative changes that may affect the acromio-clavicular joint (which sits just above the rotator cuff). Bony spurs may develop (as part of the degenerative changes) and irritate the underlying rotator cuff. Or there could be anatomical anomalies (for example an accessory bone called the os acromiale).
So when the arm is raised the rotator cuff is “pinched” between the two bones, and with time increasing damage occurs to the tendons (‘repetitive trauma to the tendon as it is squashed in the narrow space (the arch). This may result in inflammation of the tendons (“Tendonitis”) and with time degenerative changes develop in the rotator cuff tendons. This makes them susceptible to tearing if injured, and sometimes even if no injury occurs.
This is the reason that tears of the rotator cuff are more commonly seen as we get older (ie the commonest cause of a rotator cuff tear is degeneration of the cuff as we age). Trauma (from a fall, injury or sport injury) are much less common causes of a tear.
3 stages of degeneration of the tendon are recognized.
Stage I - the tendon is swollen and bruised. This is the common finding in under 25 year olds.
Stage II - the tendon is inflamed (tendonitis) with the presence of scar tissue (‘fibrosis’). This is the common finding in 25- to 40-year-olds.
Stage III - the tendon is torn, either a partial or full-thickness tear. This is common in those over 40 years old.
The early shoulder symptoms that develop from the friction occurring to the rotator cuff (and ultimately what could develop later into a tear of the rotator cuff), are known as the condition called impingement (the rotator cuff impinges against the bony prominences as the arm is elevated).
Types of Rotator Cuff Tear:
There are various types of tears of the rotator cuff:
If the tear extends through the full thickness of the tendon then it is called a “full thickness tear”.
If the tear does not penetrate the full thickness of the tendon then it is called a “partial thickness tear”.
If the affected tendon becomes detached from its attachment site to the bone then it is a “detached tear”.
If the tear of the cuff is huge then it is referred to as a ‘massive’ tear.
These differences are important as the treatment and type of surgery offered differs for the different types of tear.
Any type of tear of the rotator cuff can cause pain in the shoulder. The pain may be minimal (or there may be no pain) or severe. The severity of the pain does not always correlate with how bad the tear is. Movement of the shoulder may be very restricted, particularly trying to lift the arm above the level of the shoulder. The arm may feel weak.
Tears that develop over a long period of time, essentially due to the degenerative changes that increasingly affect the tendon, are called chronic tears.
Repeatedly performing a strenuous task with the shoulder such as throwing a baseball, or repetitive overhead heavy lifting can contribute to the degeneration of the rotator cuff in susceptible people (said to cause ‘repetitive microtrauma to the cuff’)
Rotator cuff tears can also occur suddenly, usually after a forceful movement of the shoulder; for example from a heavy fall onto an outstretched hand, or from a sudden forceful overhead throwing movement, or when lifting a heavy object above the head. But usually if the rotator cuff does tear following a sudden injury of this type it is often found that the person was susceptible to a tear occurring even though they may never have suffered shoulder symptoms before (the same mechanism of injury in another person may not have resulted in a tear of the rotator cuff).
Rotator cuff tears may also occur as part of another injury to the shoulder for example if the shoulder dislocates or the clavicle (collarbone) fractures.
What Is Rotator Cuff Tendinitis?
The term tendinitis refers to an inflammation of the rotator cuff that generally occurs as a result of impingement or overuse. Tendinitis bothers some people for a time and then seems to disappear. Their symptoms vary greatly, depending on several factors, the most important of which is how they use the affected shoulder or shoulders.
Some the tendonitis develops as a result of calcium deposits occuring in the tendon (we don't really know why). This can be very painful (or may not be painful at all). It is called a calcific tendonitis.
What Is Shoulder Bursitis?
A bursa (plural bursae) is a soft, fluid-filled sac that helps to cushion and lubricate joints. In the shoulder, there are bursae located between the rotator cuff and the overlying bone (acromion) or beneath the deltoid muscle. When a bursa becomes irritated or inflamed, it causes bursitis. Pain and swelling of the joint often accompany bursitis.
Facts about rotator cuff injury
About 6 million people in the U.S. seek medical care each year for shoulder problems.
Shoulder problems account for about 1.5 million visits to orthopedic surgeons each year in the U.S.
Rotator cuff tear is a common problem for people over age 40.