February 23, 2013
We’ve done a few blogs on the rotator cuff. Either it’s because we like writing about the shoulder or a lot of people in Burlington have shoulder pain. Regardless, this week’s blog will clarify a very important function of the rotator cuff for our readers (including our Burlington patients)…compression and depression.
We frequently see ultrasound reports at our Burlington physiotherapy and chiropractic clinic describing damage to the rotator cuff. This ranges from complete tears to partial tears, or simply just tendinopathy (or tendinitis as many call it). The pain and weakness experienced by these patients can vary. Perhaps the most obvious sign of significant rotator cuff injury would be difficulty with movements like abduction, internal and external rotation. What many people don’t realize is that another, very important function of the rotator cuff can be affected; compression and depression.
If you look at the picture below, you’ll see the arrows of force that I drew on the scapula (also known as the shoulder blade). These arrows show a downward and inward force that the rotator cuff muscles provide. This is very important for normal shoulder movement. This force allows a smooth contact of the shoulder joint surfaces. If this doesn’t happen, the humerus (bone in the upper arm) sits too high in the joint. When this occurs (and when we elevate our arms) everything above that bone in the shoulder gets squished, a condition called impingement. A person with shoulder impingement may report pain with overhead activities or exercises (like shoulder press or bench press). Think of it another way; imagine the bone sits in a groove that is shaped like a pear. At rest, the humerus (arm bone) sits in the top, narrow portion of the pear. When the rotator cuff muscles contract, they pull the humerus (arm bone) down into the wider portion of the pear. This gives the bone a larger area to move in. When the rotator cuff is dysfunctional, the humerus (arm bone) may still be sitting in the narrow portion of the pear while trying to move. Not surprising then that your shoulder gets sore with repetitive overhead work or even push-ups!
So what is the solution? Treatment is often geared toward restoring normal movements of the shoulder and eliminating muscle imbalances. This gives the humerus a fighting chance at moving in the normal part of the “pear”. In most cases, this requires clinical treatment. Along with this treatment though, strengthening of the rotator cuff muscles is usually an essential component of care. If the rotator cuff muscles aren’t performing their role of compression and depression, it’s unlikely that normal joint motion can occur and is therefore more than likely that pain and dysfunction will persist or occur at some point.
Hyde TE, Gengenbach MS. Conservative Managememt of Sports Injuries 2nd Ed. 2007 Jones and Bartlett.