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The rotator cuff is the most common cause of shoulder pain. While older individuals are most commonly affected, young athletes and workers who overuse their shoulder are also susceptible to rotator cuff problems. Although swimmers, tennis players, heavy laborers and throwing athletes are at higher risk, rotator cuff injuries are so common that they could almost be considered part of the human condition. Rotator cuff problems happen to all kinds of people, many of whom aren’t even sure how it happened.
Rotator cuff pain is usually felt on the outside of the upper arm and may even be “referred” down to the elbow. It usually occurs as you try to lift your arm over your head, reach behind your back, or when you try to sleep on your shoulder at night.
Anatomy
The shoulder is a ball and socket joint which is designed to provide great mobility.
The two muscles that allow you to lift your arm are the deltoid, the big muscle that goes over the top of the shoulder, and the rotator cuff, which is the merging of four tendons over the ball of your shoulder.
If the deltoid muscle acted alone, every time you raised your arm, the deltoid would pull the humeral head up into the acromion (the bone on top of your shoulder that the deltoid is attached to). The shoulder would just shrug, instead of allowing the arm raise up. It is the rotator cuff’s job to stabilize the ball in the socket so that this doesn’t happen. The rotator cuff keeps the shoulder’s ball centered in its socket like a golf ball balanced on a tee so that the deltoid can elevate the arm. It does this by pressing the ball into the socket so that it can’t slide up.
Many rotator cuff problems occur because the rotator cuff is a relatively small muscle-tendon unit, and the deltoid is a lot bigger and stronger.
We tend to preferentially use the big muscles of our body, and allow our smaller muscles, such as the rotator cuff, to weaken. In addition, the rotator cuff has a relatively poor blood supply and may not get enough oxygen to repair itself when overworked and damaged. For these reasons, the deltoid muscle maintains its strength better with aging and overuse. So if you don’t take care of your rotator cuff, it degenerates and becomes weak, predisposing it to becoming damaged.
Rotator Cuff Tendinosis
We used to think that the problem was rotator cuff tendinitis, which means inflammation of the rotator cuff, but since shoulder surgeons started looking at this injured tissue under the microscope we now know that this is not correct. What really happens is that the rotator cuff degenerates, without inflammation. The technical name for this degeneration is rotator cuff tendinosis.
Rotator cuff tendinosis, is an overuse injury. Overuse occurs when repetitive activity leads to tissue damage quicker than the body can heal. This repetitive trauma eventually leads to chronic tissue breakdown and pain.
As the rotator cuff gets damaged it also gets weaker. And as the rotator cuff gets weaker it is less able to hold the humeral head down in the glenoid (socket) where it belongs. So when you raise your arm up, the humeral head gets pulled abnormally higher by the large deltoid muscle. And as the humeral head rides higher, the rotator cuff attached to the top of it, contacts the bony acromion above it. This contact may further damage the rotator cuff, which further weakens it, and so on in a vicious cycle.
If the wear and tear goes on long enough the tissue can actually degenerate and lead to a full-thickness tear. Rotator cuff tearing indicates a more advanced and chronic problem. In addition to pain, a rotator cuff tear may be often associated with weakness.
Young people with rotator cuff problems should always be evaluated for shoulder instability. Even if you’ve never dislocated your shoulder (had it come out of the socket), the chronic stresses of overhead athletics or work can lead to subtle forms of instability. Shoulders become unstable when the ligaments become stretched out. When this happens, the rotator cuff has to work even harder to keep the humeral head in its socket. This predisposes to overuse of the rotator cuff, degeneration, and pain.
Treatment of Rotator Cuff Tendinosis
There is a balance between the stresses that you apply to your shoulder, and the strength your rotator cuff has to handle this stress. When the stress applied exceeds what the rotator cuff can handle, over time tissue damage may occur. To treat mild or moderate rotator cuff damage you can either lower the stres or increase the rotator cuff’s strength so that it is able to handle the stresses that are being applied.
If your shoulder hurts every time you raise up your arm, you can avoid pain by not raising your arm up. If you do this for long enough your shoulder may quiet down and not hurt so much. The problem is that the shoulder has a distinct “use it or lose it” character, and this strategy can lead to permanent stiffness.
The better treatment is to increase the strengthe and endurance of the rotator cuff. This is done through strengthening exercises. In many cases these exercises are all that is necessary to cure the problem, especially if you catch it early.
A steroid injection will not provide permanent cure, but it often provides pain relief to allow you to sleep comfortably at night and to do your exercises better. The pain relief lasts an average of 3 months. As in other areas, multiple injections into the same area can lead to tissue weakness and damage, and should be discouraged.
A full course of appropriate rehabilitative exercises should usually be undertaken prior to the consideration of surgery. Surgery is only reserved for failure of non-surgical management.
Most shoulder surgeons still use some variant of a procedure called the “subacromial decompression” to treat rotator cuff problems. The reason they do this is because in 1972 a famous shoulder surgeon said that a ‘bone spur’ from the bone above your shoulder (the acromion) is what causes rotator cuff problems.
However, essentially all of the evidence gathered since then states that this is simply not true. As previously noted, it is now known that rotator cuff pain is caused by degeneration of the rotator cuff tendon itself. In the vast majority of cases, the “impingement” of the rotator cuff against the undersurface of the acromion (bone) is the result of rotator cuff dysfunction, not the cause.
Not only is this bone removal often unnecessary, it can cause additional pain and stiffness, and potentially compromise future shoulder function.
The undersurface of the acromion is, in the vast majority of individuals, a normal structure that is designed to act as a ‘back-up system’ to help elevate the shoulder after the rotator cuff naturally weakens and degenerates with age. It is often preferable to leave the acromion bone intact. In addition, the subacromial decompression does nothing to remove unhealthy rotator cuff tissue, which is usually the primary source of pain.
A newer, and much more direct procedure, Arthroscopic Rotator Cuff Debridment (ARCD) involves simply removing the unhealthy rotator cuff tissue, while leaving the normal structures alone.
Arthroscopic rotator cuff debridmenet (ARCD) minimizes post-operative pain, and long-term problems. If there is a rotator cuff tear, it is repaired arthroscopically. If the shoulder is unstable, it is stabilized arthroscopically.
Summary
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