you have suffered a shoulder injury, you have probably injured your
shoulder ligaments. The ligaments of the shoulder help to hold the
humerus in the socket, and to provide stability to the joint. The
shoulder joint capsule is often injured in sports, especially with
dislocations and shoulder sprains.
we will look closer at shoulder
anatomy, focusing on the ligaments and joint capsule.
vs. Joint Capsule
shoulder joint capsule is a band of connective tissue that encapsulates
the head of the humerus. It helps to hold the humerus in the glenoid
(socket) when the shoulder is at rest. While many people think about
ligaments connecting bones, the joint capsule plays an important role
in this function. Unlike the knee, which has ligaments that are
individual bands of tissue, the shoulder has thickenings in areas of
the joint capsule that are referred to as ligaments. Let me explain...
shoulder ligaments are not seperate from the joint capsule. In fact,
they aren't really ligaments at all, in the way you think about
ligaments like the ACL or PCL in the knee. They are simply areas of
tissue that are thicker than the other portions of the capsule. So,
your physician may refer to the shoulder ligaments as part of the
capsule, or as ligaments, but they mean the same thing.
shoulder has 3 different areas of thickening in the capsule, which can
be referred to as ligaments. These are the anterior glenohumeral
ligament, inferior glenohumeral ligament, and posterior glenohumeral
The ligaments provide stability to the
help to restict excessive joint motion. Notice in the picture how the
inferior ligament (or capsule) seems to hang down from the humerus.
This is important as we talk about shoulder function.
anterior shoulder capsule helps to restrict forward motion of the
humerus. It also helps to restrict external rotation. As will all
ligaments and joint capsules, the shoulder ligaments all become tight
with different motions. The anterior capsule becomes tight when the
shoulder is flexed above 90 degrees, or when it is externally rotated.
anterior glenohumeral ligament is the tissue that is injured with 95%
of all shoulder dislocations
When the shoulder dislocates, it almost always comes forward and down.
This stretches and tears the anterior part of the joint capsule, and
the anterior glenohumeral ligament.
for shoulder dislocation is when the arm is out to the side, above
shoulder level, and the elbow bent to 90 degrees. In this position, the
anterior capsule and ligament is tight...forced motion in this position
will significantly stress the capsule, and can cause damage.
inferior glenohumeral ligament is a redundency of the shoulder capsule.
In the picture you can see how it hangs down from the humerus...almost
like there is too much tissue there. This isn't the case.
see, when the shoulder moves, the capsule must be able to stretch and
adapt. If the inferior capsule was not hanging down, you wouldn't be
able to raise your arm over your head. When the arm is raised above
shoulder level, the inferior capsule begins to tighten.
inferior capsule is not usually injured during sports...however, it can
become excessively tight if the arm is immobilized for an extended
period. Ever heard of frozen shoulder? This is the part of the capsule
that often tightens down and causes frozen shoulder.
posterior shoulder ligaments, or the posterior glenohumeral ligament,
help to prevent excessive internal rotation of the shoulder, and
excessive shoulder flexion. It is not usually injured during sports,
because most dislocations occur anteriorly. However, it can cause
problems when it gets tight. This is very true with overhead throwers.
Pitchers often have a very tight posterior capsule, and this can
contribute to injuries such as shoulder impingement syndrome.
shoulder ligaments and joint capsule play an important role in shoulder
stability and function. They provide the necessary restrictions to
excessive motion. While the vast majority of sports injuries involve
the anterior portion of the capsule, the posterior capsule can be
involved with injuries like impingement syndrome.
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