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Shoulder Socket-Ball Joint Muscle Imbalance


How did you go seeing on your clients how the cable pull movement can be different on different bodies? As we saw last Friday, Pec Minor is a real bugger for many people… and I do think that Lower Trapezius is one of the most commonly weak muscles in all humans.

In this Rehab Friday we are keen for you to understand some of the deep biomechanics of shoulder impingement – so make sure all your Medical and Physio colleagues also get a chance to read this as it makes simple something quite technical: the classic Muscle Imbalance within the Glenohumeral Joint, or what I call, the “Socket-Ball Joint”.

Yes – the “Socket-Ball”, not the Ball and Socket! Think about it…Gleno = Socket, Humeral = Ball. The tricky part of the shoulder is the Socket-Ball Joint.

This muscle imbalance within the Socket-Ball Joint is the central cause of internal shoulder pain like Sub-acromial impingements. It revolves around the two External Rotators of the Rotator cuff (Infraspinatus and Teres Minor) dominating the Internal Rotator Subscapularis. In a correctly balanced functional movement, these rotators should be in even tension so that the ball stays in the socket. The main thing to work on, as in all muscle imbalances, will be tightness of the overly-dominant muscle.

The solution? Hands on loosening and trigger point work.

If you look at the image of the athlete’s shoulder above on the left, you will see how the dominant External Rotators can also affect the standing posture. Over-activity of the External Rotator cuff will over time pinch the ball in the socket and shear it forward so it protrudes anteriorly like in the picture.

The image on the right demonstrates a quick and useful assessment technique for the same muscle imbalance, which is also the topic of today’s video. If the functional movement of reaching up behind your back looks difficult or dysfunctional, then this is evidence that there is muscle imbalance and tightness.

Once again, the solution is hands-on loosening and trigger point work. Refer to our recent video on Shoulder Impingement for how to release this tightness.

Here’s to the Skills of Seeing, and easy back scratching!


Practice your Skills Of Seeing with our 5 Classic Muscle Imbalances that we have named and shamed in our recent series. If you missed some of them go back to our Videos room on the website to refresh your memory.