What
Goes Wrong with Your Rotator Cuff
(also
see 4 Exercises to Avoid
and Rotator Cuff Tendinitis)
The rotator
cuff consists of four muscles that run from the shoulder 
blade to the the upper arm, or humerus. Actually,
physiologists think of the cuff as being the tendons of these
four muscles—tendons are what connect muscle to bone—but from
the perspective of preventing or rehabilitating shoulder injuries,
it makes more sense to consider both tendons and muscles.
The four
muscles of the rotator cuff are:
- supraspinatus
- infraspinatus
- teres
minor
- subscapularis
In simple
terms, these four muscles stabilize the shoulder. If, for some
reason any of them can't do its job, major motions of the shoulder
become impossible—forget throwing a ball, bench pressing, or
even combing your hair!
Together,
the four muscles of the healthy rotator cuff:
1. Counterbalance
the upward pull of the deltoid muscle on the humerus
The deltoids
are the major muscles responsible for raising your arms. Since
they run downward from the collarbone to attach along the side
of the humerus (upper arm), they would tend, when contracting,
to pull the humerus straight up, jamming the top of the bone
against the roof of the shoulder joint. Rotator cuff muscles
prevent this by pulling the head of the humerus down just enough
to prevent the collision and to allow the humeral head to move
freely.
2. Externally
rotates the shoulder
If you try
to raise your arm with your thumb pointing down, you'll find
you can only raise it about 80 or 90 degrees. (Sure, go
ahead: try it.) This is the point at which the greater tubercle
(a bony bump on the side of the humerus where various muscles
are anchored) crowds the shoulder joint, impinging on the tendons
and bursa that run there. Only by externally (or outwardly)
rotating the shoulder are you able to raise your arm any higher.
This external rotation is performed by two of the rotator cuff
muscles.
3. Provide
a stable base for the major motions of the shoulder joint
The dish-like
socket of the shoulder joint is extremely shallow, and is stabilized
by muscles and tendons surrounding it. The four muscles of the
rotator cuff act like guy wires supporting a tent pole, each
pulling from a different direction to hold the joint securely
together while it's in motion.
4. Decelerate
the arm when you throw something.
Throwing
motions involve the cuff in two ways. First, throwing a ball
is basically an attempt to throw your arm away from your body.
The rotator cuff muscles, along with several others, prevent
you from succeeding. Second, although throwing involves several
actions at the shoulder, it really amounts to a case of high-powered
internal rotation. It's the external rotators—the infraspinatus
and teres minor—that put on the brakes at the end of the motion.
What Goes
Wrong
If the cuff
is damaged, it may not be able to perform the functions listed
above. Many conditions, some mild, some severe, can keep the
cuff from doing its jobs properly. Some of these include:
- chronic
degeneration
- inflammation
(various conditions ending in ``—itis")
- calcium
deposits
- tears
- impingement
- joint
contracture and adaptive shortening
- muscle
imbalance
- fibrosis
- injury
The Underlying
Problem: Dysfunctional Shoulder Biomechanics
The most
important thing to know about cuff injuries is that often the
obvious injury—the tear, the inflammation, the fibrosis (all
these terms are covered in The 7-Minute Rotator Cuff Solution)—simply
represents the tip of the iceberg. The actual iceberg is dysfunctional
shoulder biomechanics—basically, improper functioning of the
joint. Dysfunctional shoulder biomechanics, brought about by
repeated improper training, consists of a potpourri of conditions,
including:
- a muscle
imbalance between the internal and external rotator muscles
- adaptively
shortened internal rotators (with possible scarring, called
fibrosis, of tendons and muscle)
- inflamed
rotator cuff muscles (with possible fibrosis)
What
You Can Do
To be effective,
a rotator cuff program must address all the components that
contribute to dysfunctional shoulder biomechanics. It must...
- strengthen
the external rotators
- stretch
the internal rotators
- eliminate
the training errors that promoted inflammation and started
the ball rolling toward dysfunctional shoulder biomechanics
in the first place
A program
like this will be equally effective at rehabilitating the injured
cuff and preventing injury in the healthy one.
-
Also see 4 Exercises
to Avoid
and Rotator
Cuff Tendinitis
