The Shoulder is Like a Golf Ball?

What is the shoulder? The shoulder, or glenohumeral joint, is simply a ball and socket. This is similar to a golf ball sitting on a tee with a ball being the head of the humerus (upper arm bone) and the tee being the glenoid fossa (a socket formed from the shoulder blade).

 

Only about 1/3rd of the joint surface of the ball contacts the tee at any time. Because the ball is bigger than the tee socket, more movement is allowed in the shoulder. Ligaments normally bind bone to bone over a joint to help hold the two parts together for stabilization. When the ligaments are tight, there is less movement. However, the shoulder is very mobile as you can see in the picture below. In order to allow more mobility, the ligaments need to be laxer. We sacrifice stability for mobility. For this reason, it is easily dislocated. A joint with less stability therefore depends on the surrounding structures such as muscles and ligaments to protect itself from injury.

 

shoulder movement

 

So, what muscles help the shoulder complex protect the joint to produce movement? The four rotator cuff muscles play an important role in initiating movement overhead while also keeping the ball in the tee socket to maintain stability. Of the rotator cuff muscles, the supraspinatus is the primary mover. Yet, it doesn’t act alone. The infraspinatus and teres minor help upwardly rotate the shoulder blade so the subscapularis can depress the ball within the tee socket so it doesn’t impinge against the top edge of the tee causing pain.

muslces of rotator cuff   deltoid muscle

 

 

 

 

 

 

 

Once the rotator cuff is done initiating, the Deltoid kicks in and acts in synergy to continue overhead movement.

 

After the deltoid, the Serratus Anterior and both the Upper Trapezius and Middle Trapezius continue outwardly rotating the shoulder blade. Closer to end range, the Lower Trapezius finalizes the movement.

 

serratus muscle

scapular movement   

 

As you can see, if just one of these muscles isn’t functioning properly, the shoulder can’t rely on the surrounding structures to protect itself from injury. This is where you may notice pain when reaching overhead and may need to seek further evaluation from a physical therapist to find the weakest link.

 

But before seeking further evaluation, try these four exercises to fix the movement.

 

The infraspinatus and subscapularis of the rotator cuff like to tighten the shoulder joint when irritated. Both muscles help the arm reach overhead, but more specifically, the infraspinatus performs external rotation while the subscapularis performs internal rotation. Opposite actions, right? When they are both tight, your shoulder can’t move.

 

In previous posts and on our YouTube channel, we have talked a lot about how cross friction massage and active release techniques are beneficial for stretching muscles to create healthy tissue. Check out the Not So Common Elbow Pain blog post to review rolling the subscapularis with a softball and yoga block along with a lacrosse ball on the infraspinatus. These are the first two exercises.

 

Once you’ve loosened up those muscles, this wall slides drill will help re-train the serratus anterior to help upwardly rotate your shoulder blade. Remember from the picture above, the serratus anterior hugs the ribcage. We want to promote movement of the shoulder blade on the ribcage with this exercise. To begin, place your forearms and pinkie along the wall with elbows bent like the picture below. Then, slide your hands up the wall. While doing so, really focus on reaching through your shoulder blade to push away from the wall. Think about your shoulder blade reaching around your rib cage until it’s under your armpit. Your shoulder blades will become rounded, aiding the serratus anterior in hugging the ribcage. Try two sets of ten. Stop this exercise if it becomes too painful.

 

wall slides

Lastly is an exercise called a push up plus to help improve serratus anterior strength for complementing the wall slides. Begin in a push up position. Lower your body until your chest is almost touching the floor. Then, push yourself back to the starting position where your elbows are straight. Continue pushing your palms into the floor to drive your shoulder blades up to the ceiling so they become rounded. If this push up position is too uncomfortable, try it out against a wall. Two sets of ten again.

 

push up

Hopefully these exercises help to alleviate your shoulder pain and increase your movement. If you are not seeing results after two weeks, seek help from a medical professional for further evaluation.

 

Megan Shaia
DPT student, Clarkson University
Winter Intern

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