Although
back pain, neck pain, and headaches are the three most common reasons why
individuals seek out the services of a chiropractor, shoulder pain is another
frequent complaint seen in the office.
Sometimes there is a traumatic mechanism to explain the onset of pain,
such as a fall or over-exertion with lifting, reaching, pulling, or throwing
types of activities. However, often the cause
is not very obvious, suggesting that a more cumulative process has resulted in
a pain experience at the shoulder. Discussing
the structure and function of the shoulder will help us understand how this may
occur. Note - it is also important to
realize that pain felt at the shoulder may not have its origin at the shoulder
at all but instead have a more central source, commonly the neck region, with
structures either referring or radiating pain to the shoulder, with or without
the presence of neck discomfort.
The
shoulder is a ball and socket joint. As
such, it is a very mobile joint with many movement possibilities, but with
greater potential for instability as well.
The "ball" is the head of the upper arm bone called the
humerus and the "socket" is a shallow depression on the shoulder
blade, made deeper only by the addition of projections of cartilage called the
labrum. The shoulder blade essentially
floats on our mid back by way of muscular attachments with its only direct bony
connection to the rest of our skeleton being made via the collar bone. The four rotator cuff muscles attach the ball
to the shoulder blade and function to keep the ball centred in the socket while
larger muscles around the shoulder, the deltoid and "pecs" for
example, create the actual movement of the shoulder/arm. With ranges of motion, the ball rotates and
glides in the socket, the shoulder blade itself moves in a variety of
directions, and the collar bone rotates and tilts. The mid back also needs to extend. All of these motions have a pre-wired
sequencing or rhythm in which they occur to move the shoulder optimally and
basically keep the ball in the socket.
When this pattern of motion is altered due to a new injury or persists
after an older problem resolved but wasn't fully rehabilitated, or simply as a
result of postural imbalances, this sets the stage for future trouble.
Unlike
other joints in the body where the muscles that move and/or stabilize the joint
surround the bony connection, the shoulder is unique in that some soft tissues
(i.e. rotator cuff muscles and tendons, bursae) are contained in an area
surrounded by bony structures. To orient
you, feel the bony tip of your shoulder blade, named the acromion, where the
shoulder slopes down to become the arm.
The area beneath the acromion is appropriately called the sub-acromial
space, which houses those soft tissues, sandwiching them between the ball of
the ball and socket below and the acromion above. If the rhythm mentioned previously becomes
altered and the ball is not well maintained in the socket throughout ranges of
motion, these tissues can become overly pinched, or "impinged"
between the bony surfaces. Over time
this can result in a number of different painful conditions, such as bursitis,
a biceps tendonopathy, a rotator cuff tear or tendonopathy, shoulder
impingement syndrome, and arthritis to name a few.
Part
2 of this article will continue this discussion and suggest a few things one
may try to help optimize shoulder function.
This article is for general information purposes only and is not to be
taken as professional medical advice.
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