Updated November 2017
Understanding what is happening inside of the shoulder joint is a very important part of understanding impingement. If you haven’t checked out part 1 and part 2 I’d recommend starting there before reading about the shoulder blade. To make matters a bit more complex, the musculature that surrounds and controls the shoulder blade (scapula) plays a large role in this condition as well. I wanted to leave no stone unturned in fully understanding impingement so next we’ll discuss how the scapular musculature can affect impingement.
Patients with impingement have changes in shoulder blade kinematics that differ from healthy patients. Basically this means that the shoulder blade is not moving normally as it should in pain free patients. In the world of shoulder pain and pathology, this is often referred to as scapular dyskinesia.
Why is this happening? Part of the problem lies in what is happening to the musculature that attaches to the shoulder blade. Similar to issues with the rotator cuff in impingement, we’re having these problems in scapular musculature. These dysfunctions can present as:
The problems associated with the scapular musculature is thought to alter the orientation of the humeral head in its socket and decrease the subacromial space and decrease cuff strength (8). As discussed earlier, a decreased subacromial space can compress the rotator cuff tendons, bursa and the biceps tendon. If we want healthy shoulders we’ve got to address this area.
Here’s what we typically see out of whack in this population:
1. Patients with Impingement had on average greater recruitment of the upper trapezius and less recruitment of the lower trapezius when raising their arms overhead in the scapular plane. This upper trapezius dominance can cause hiking or shrugging of the shoulder during overhead movement and decrease the ability of the scapula to rotate normally.
Taking a look at where the trapezius originates and inserts (attachment points to bone) you can see that the upper trapezius will be responsible for elevating the scapula and rotating it upward as you elevate them arms overhead. The lower trapezius will be responsible for keeping the shoulder blade stable and keeping it from excessively elevating. The lower trapezius counterbalances the upper trapezius and allows the scapula to rotate normally. Lastly, if the lower trapezius is not doing its job correctly then the upper trapezius will do more hiking/shrugging as opposed to rotating the scapula normally as you raise your arms overhead.
2. Those with impingement typically have either a weakness or delayed activation of the middle/lower trapezius as well as the serratus anterior. These muscles play a large role in stabilizing the scapula flat against the ribcage with movement.
A Brief Side Note on Posture:
Abnormal (flexed thoracic spine and rounded forward shoulders) posture is often a culprit for people with shoulder pain. It is often used by therapists and health care providers as a common cause of shoulder pain and subsequently as a reason why people can’t seem to get rid of their shoulder pain. However, recent research has failed to correlate any sort of shoulder posture (flexed spine, rounded shoulders) with shoulder pain (9). Although this doesn’t eliminate the idea of better postures potentially being more healthy for the shoulder, it does decrease the likelihood of it being a cause of pain.
3. Scapular dyskinesis is basically abnormal position of the scapula with movement. Normally the scapula should slide flat on the ribcage and rotate normally as your bring your arms overhead. This helps keep the shoulder centered in its socket and minimizes stress on the subacromial space. In those with impingement the shoulder blade can be anteriorly tilted, elevated and may not upwardly rotate as much as it should. This becomes evidence when you watch these patients raise their arms overhead or do pushups.
Notice how this woman’s shoulders are shrugged up while attempting a pushup against the wall. Also notice her left shoulder blade looks as if it is lifting off the ribcage.
Scapular dyskinesia is something we definitely see in individuals with shoulder pain. Trouble is, there is generally not a standard sort of dyskinesia we see in patients with shoulder pain (11). In other words, each individual with shoulder pain will move their scapula a little bit differently then another with shoulder pain. Also, research to support dyskinesia leading to shoulder injury is conflicting and generally only present in very specific populations at an elite sporting level (10). Also, individuals with shoulder pain tend to get better with exercise even if it isn’t specifically targeted towards addressing scapular dyskinesia. Although it seems prudent to design rehabilitation programs centered around potential scapular problems seen in patients, it might not be necessary.
Next we’ll talk a bit about the thoracic spine and rib cage and how it effects the shoulder in impingement. I’m pumped!
Just a few things covered in the course…
Is scapular dyskinesis a real word or did you just make it up?
Dan Pope DPT, OCS, CSCS, CF L1
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Shoulder Impingement: Part 4 – The Thoracic Spine and Ribcage’s Role in Impingement
Shoulder Impingement: Part 2 – What Happens at the Shoulder Joint During Impingement
Shoulder Impingement: Part 1 – What It Is and Why It’s Important