Shoulder Impingement

By Rob Parker, Physical Therapist

So your doctor says that you have shoulder impingement or impingement syndrome. What does that mean and what do you do about it? 

There are two kinds of impingement problems, one outside the shoulder socket and one inside.

Impingement outside the shoulder socket is the most common. Pain is caused by irritation of the rotator cuff tendon and/or the bursa (an oil sack for the shoulder) being pinched between the bones. This pain can be felt in different parts of the shoulder, neck, or upper back. It is often worse at night and gets worse when lifting the arm or putting your hand behind your back.

In the human shoulder, a bony hood is formed where part of shoulder blade (acromion) and the collar bone (clavicle) come together. This bony hood sits over the top of the upper arm bone (the humerus) forming a tunnel just above the shoulder socket (glenohumeral joint.) In the space between this hood and the top of the humerus sits one of the tendons of the rotator cuff as well as a bursa. There is not very much room in this little tunnel, so if the humerus and the acromion bump into each other, the structures between them get pinched and can swell, causing pain. This results in impingement outside of the joint. 

This type of impingement can be caused by anything that either (a) moves the arm up into the acromial hood or (b) moves the acromion down onto the top of the arm bone. Repetitive overhead movement, such as throwing or painting overhead, can cause the arm bone to move up and rub on the bottom of the acromion. Other problems such as bad posture or weak shoulder blade muscles can cause the acromion to move downward, causing the impingement. 

The most common treatment for impingement outside the shoulder socket is to stop or limit the offending motion, to use ice and anti-inflammatory medication to reduce the swelling, and strengthen the rotator cuff muscles. It is also important to restore normal posture and increase the strength of the muscles that control the shoulder blade’s position. If the impingement has been going on for a long time, the tendon may be damaged. Damaged tendons can sometimes be rehabilitated with exercises unless the damage is too significant. Significant tendon damage or tearing may require surgery.

The less common type of impingement is called internal impingement. 

The socket of the shoulder is called the glenoid fossa. This part of the bony shoulder blade is shallow and pear shaped. It has a small ring of gristle-like material that surrounds the outer rim. This cartilage ring, called the labrum, deepens the shallow socket. 

Internal impingement causes pain in the back at the shoulder and often has a popping sensation associated with arm movements. It is caused when the top of the humerus bangs against the inside of the shoulder socket toward the back. This trauma can damage the underside of the rotator cuff tendons and tear the labrum.

What causes this banging in the back of the joint? If rotator cuff muscles are not well balanced improper shoulder joint motion can occur, leading to internal impingement over time. If the back of the shoulder is very tight and there is a resulting loss of the ability to reach behind the back, internal impingement can also occur over time. 

People who have excess mobility in their shoulder can slightly dislocate the humerus forward toward their chest. When it comes back into the socket, it can go too far, damaging the structures. This injury can also occur when bracing for a fall forward onto an outstretched arm. This jams the humerus against the back of the socket, causing damage. 

The early-stage treatment for this problem is the same as for outside impingement; i.e., rest, ice, anti-inflammatories, improving posture and strengthening of the shoulder blade muscles. If the painful shoulder popping is not resolved with this treatment, then surgery may be required to repair damaged tendons , fix the torn labrum, or even tighten the shoulder socket.

 

Rob Parker, PT, OCS, MS, ACT, COMT

Physical Therapist Rob Parker is medical advisor to Therapeutic Dimensions Inc.