Hey everyone, Dr. Lell here. Today’s topic is shoulder impingement syndrome; a pretty common condition that’s typically not investigates to the fullest extent. There are four classifications of this condition but I’ll just be covering the most common one – primary mechanical impingement. Let’s go over some of the simple anatomy first.
The important players are the scapula (shoulder-blade), supraspinatus muscle (posterior rotator cuff), and a tunnel called the subacromial space. The space is what’s really important. Take a look at the diagram. That unlabeled space above the glenoid fossa and below the acromion and clavicle is the subacromial space (let’s just call it the space). What’s not pictured is the supraspinatus muscle which is inside the space and attaches to the upper arm.
That’s about as technical as we’ll get.
What causes impingement syndrome? -Anything that causes that area in the space to get smaller. The big three things that cause this are:
- The content in the space gets bigger. There’s stuff in that tunnel. Most notably, the supraspinatus muscle and a bursa. If a person has been using that arm a lot (swimming, working overhead, throwing), then the contents can get irritated/swollen. I usually see this in the younger athletic population.
- The walls of the tunnel get bigger causing the space to get smaller. Years of wear and tear or a single large injury can cause changes in the joints and bones making the amount of free area in the space smaller. Alternatively, some people can be born with a misshapen bone; this will have the same effect. I usually see this in the older populations.
- The scapula is unstable during movement. The roof of the space is the scapula. The scapula isn’t strongly locked into place like other bones of its size but it’s held down by many muscles coming from many different directions. If those muscles are unbalanced, the scapula can have too much free motion which consequently changes and decreased the area in the subacromial space. This scapular instability or scapular dyskenesis is what I see the most of in non-athletic patients under 60; especially in people who sit at computers a lot. Sometimes this can cause irritation of the space’s contents and then you end up with what was described in scenario 1.
How you treat impingement syndrome relies on what’s causing it. Scenario 2, the degenerative changes, is more anatomical than functional and may not respond to conservative care as well as the other two, which respond very well to to electrotherapy and active care.
I generally approach this condition functionally. Once any inflammation or pain has been decreased, I like to give the patients ergonomic advice along with stretches and exercises that they can do at home to prevent future flare-ups.