When you hear someone say “I have a torn rotator cuff”, the supraspinatus is usually what is being referred to. Even though the supraspinatus is just one of four muscles that make up the cuff, it is by far the most often injured. Understanding how the supraspinatus works is key to understanding why it’s easily injured and what you can do about it.
The suprispinatus originates on the upper border of the scapula and inserts onto the humeral head. Its functions include:
1. Raising the arm to the side (abduction: away from the midline of the body). Imagine you are doing a dumbbell side raise. The supraspinatus will be responsible for the first 15-30 degrees of abduction. From there your deltoid takes over much of the movement.
2. Most importantly, the supraspinatus keeps the humeral head in the socket while performing such actions as military pressing, throwing a baseball, serving a tennis ball, or doing dumbbell shoulder side raises.
Keep in mind the “golf ball on the tee” analogy. The socket is very shallow and has a small surface area. If the supraspinatus weren’t there to hold the humeral head in place, the humeral head would roll out of the socket very easily. Have you heard of shoulder dislocations? A dislocation is when the humeral head completely comes out of the socket. If the rotator cuff, and especially the supraspinatus, were not active in keeping the humeral head in place, your shoulder would dislocate (or sublox, which is a minor dislocation) constantly.
The Supraspinatus is #7
In the picture above, the supraspinatus is #7. Notice how it starts on the scapula (on the right side) and inserts on the top of the humeral head (on the left). The fact that the supraspinatus originates on the scapula means that the scapula is of utmost importance in maintaining rotator cuff health. You’ll understand better when I discuss the role of scapular stability in the next post.
{ 2 trackbacks }