The shoulder
is made up
of three
bones: the scapula (shoulder
blade), the humerus (upper
arm bone),
and the clavicle(collarbone).
A part of
the scapula,
called the glenoid,
makes up the
socket of
the
shoulder.
The glenoid
is very
shallow and
flat. The
labrum is a
rim of soft
tissue that
makes the
socket more
like a cup.
The labrum
turns the
flat surface
of the
glenoid into
a deeper
socket that
molds to fit
the head of
the humerus.
The rotator
cuff connects
the humerus
to the
scapula. The
rotator cuff
is formed by
the tendons of
four
muscles: the supraspinatus,
infraspinatus,
teres minor, and subscapularis.
Tendons
attach
muscles to
bones.
Muscles move
the bones by
pulling on
the tendons.
The rotator
cuff helps
raise and
rotate the
arm. As the
arm is
raised, the
rotator cuff
also keeps
the humerus
tightly in
the glenoid
of the
scapula.
The soft
labral
tissue can
be caught
between the
glenoid and
the humerus.
When this
happens, the
labrum may
start to
tear. If the
tear gets
worse, it
may become a
flap of
tissue that
can move in
and out of
the joint,
getting
caught
between the
head of the
humerus and
the glenoid.
The flap can
cause pain
and catching
when you
move your
shoulder.
Several
tendons and
ligaments
attach to
the labrum
that help
maintain the
stability of
the
shoulder. So
when the
labrum
tears, the
shoulder
often
becomes much
less stable.