At its very basic level, rotator cuff tendonitis is a muscle imbalance problem. Scientific research states that 90% of shoulder pain has at least something to do with the rotator cuff. To understand what is going on there, you need to understand the role of the rotator cuff.
The rotator cuff acts as a counterbalance to the larger muscles that are trying to move the arm. If not for the rotator cuff, as the deltoid, trapezius, or pectoralis muscles move the arm, the head of the round ball on top of the arm bone would slip out of the very shallow dish that it is in. This is called the glenoid fossa.
All movements require a very complex system of essentially muscles moving in two different directions to keep this big ball sitting on a tiny dish. The one thing you notice about shoulder pain as a practicing physician is it can happen to people who are in bad shape, people who are in good shape – it just happens.
One thing that we often see in our office is what we call a “high-riding shoulder”. This process is the result of a relative weakening of the floor muscles of the rotator cuff when compared to the overlying muscles of the deltoid, pectoralis, and trapezius muscle groups.
The muscles involved lead to an upward migration of the humerus and the humeral head (the big ball), that compresses the supraspinatus, one of the muscles of the rotator cuff up against the roof of the shoulder, which is very hard, and this compromises its blood flow, leading to significant stress and disease within the rotator cuff.
This process occurs to many people on a daily basis. The main reason for this problem is that people continue this muscle imbalance. There are great exercises for the larger muscle groups and for the small muscle groups as well. However, the small muscle exercise groups are not as well-known, but are actually very easy to do.
I think when people come to understand that it is a muscle imbalance problem more than anything is when we will start to make some inroads into solving the nearly universal problem of shoulder pain and rotator cuff tendonitis.