AC Joint Impingement vs. “Regular” Shoulder Impingement
Posted Jul 07 2010 4:32am
I’ve seen a few acromioclavicular (AC) joint impingement cases at our facility in the last couple of weeks and thought it’d be good to do a quick blog to talk about how different they are from “regular” (external) shoulder impingement cases. And, it is a very important differentiation to make.
While I talk a lot about the symptoms for both, several provocative tests for these issues, and training modifications to avoid exacerbating pain under these conditions, there was one important “differential assessment that I missed.” Mike Reinold actually taught me it as we were planning the Optimal Shoulder Performance DVD set.
Just paying close attention to (and asking about) where folks have their pain during overhead motion can tell you quite a bit. In an external impingement - where we’re talking about the rotator cuff tendons and bursa rubbing up against the undersurface of the acromion - you’ll usually get pain as folks approach 90 degrees of abduction (arm directly out to the side). That pain will persist as they go further overhead, and in my experience, start to die off as they get to the top.
Conversely, for those with AC joint impingement - what is essentially bone rubbing up against bone - you see a “painful arc” only at the last portion of abduction:
You can usually confirm your suspicions on this front with direct palpation of the AC joint and checking to see if folks have pain when reaching across the chest.
Much of the training modifications will be the same for these two conditions, but there are also going to be several key things that should be managed completely differently. For instance, front squatting someone with an AC joint issue would not be a good idea due to the direct pressure of the bar on the AC joint; it would, however, be just fine for most cases of external shoulder impingement. In another example, some serious AC joint issues are exacerbated even by just doing the end-range of a rowing motion (to much shoulder extension/horizontal abduction) - whereas even folks with full-blown rotator cuff tears can generally do rows pain-free.