I see a lot of people with shoulder problems. A LOT of people. Athletes. Senior citizens. Young kids. A few more males than females. At times, it seems as though there is a shoulder epidemic.

A little anatomy lesson: In health class, you may have learned that the shoulder is a “ball and socket” joint. It really isn’t. The hip is. And because of that, the hip is inherently more stable. It takes a huge trauma to dislocate the hip. Usually a car wreck. The shoulder? Not so much. But back to that in a moment.

There really isn’t a socket to the shoulder. Instead, there is a cavity, if you will, formed by several bony prominences — most of which are part of the scapula, known commonly as the shoulder blade.

There is the acromion, the glenoid, and the coracoid process, all part of the scapula. Throw in the end of the clavicle (or collarbone) and you get the “socket” part of the shoulder. The upper arm bone is known as the humerus and the head, or top of the humerus does resemble a ball.

But the shoulder is dependent on a group of muscles called the rotator cuff to hold it all together. That’s unlike the hip, where the top of the femur (upper leg bone) fits firmly into the socket of the hip that we know as the acetabulum.

And it’s not “rotor cup” or “rotary cuff” or any of the many, many names that I’ve heard it called through the years. It’s the rotator cuff. Why? The rotator cuff is a group of four muscles that surround the head of the humerus and hold it in place, in addition to performing a lot of other very important functions in shoulder function.

The Supraspinatus, Infraspinatus, Subscapularis, and Teres Minor are the muscles that make up the rotator cuff. They are all fairly small, relatively flat muscles that form a “cuff” of muscles around the head of the humerus. Without them, shoulder function is severely limited.

Without a healthy rotator cuff, you can’t throw much of anything. The bigger muscles around the shoulder are what gives you throwing velocity but without those small muscles of the rotator cuff, you’ll never find home plate or the open receiver.

So when problems occur, athletic function can be seriously impaired. Problems can range from more simple tendonitis to tears of the rotator cuff. And since shoulder doesn’t have the built-in stability of a joint like the hip, it can come out of joint. The most common mechanism for a shoulder dislocation is a fall on an outstretched arm. If it’s out, you will know it.

More common is a shoulder subluxation, in which the head of the humerus moves slightly out of the socket and then goes back in place on its own. With subluxations, the rotator cuff is likely not doing its job of holding the shoulder in place. There can be a lot of reasons for that. Repeated trauma. Muscle imbalance.

And posture. I see more shoulder problems that are due to posture than anything else. Let me try and describe what I see. For different reasons, the shoulders can be turned in and are in front of where they should be. If I look at someone from the front, what I may see is the back of their hands.

In good posture, the hands are at your sides, maybe slightly turned in. What all this means is that the head of the humerus is sitting in the front part of the shoulder socket (OK, I call it that too, even though it isn’t really a socket). The problem is that this is where the most vulnerable part of the rotator cuff is found.

This forward position of the head of the humerus puts a lot of pressure on the rotator cuff, compromising it in several different ways. It can even ultimately wear a hole in the rotator cuff.

That’s why the basic solution for a lot of shoulder problems is to correct the posture through strengthening the muscles on the back of the shoulder, particularly those muscles that pull the scapulae back toward the spine. And that’s where I come in.

Joe Black, PT, DPT, SCS, ATC is a physical therapist and athletic trainer at Total Rehabilitation and is Manager of Outpatient Rehabilitation for Blount Memorial Hospital. Email joeblackdpt@gmail.com to write to him.

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