(AC) joint is located at the end of the clavicle (collar bone)
toward the shoulder. It is where the clavicle meets a part of
the scapula called the acromion. When this joint is disrupted,
it is called a shoulder separation (also called an acromioclavicular
joint separation, or AC separation). This joint may also become
arthritic due to previous injury, the aging process, or other
A shoulder separation
is almost always the result of a sudden, traumatic event. This
is often due to either a direct blow to the shoulder (often
seen in football, rugby, or hockey), or a fall on to an outstretched
hand (commonly seen after falling off a bicycle). Pain is the
most common symptom of a separated shoulder, and is usually
severe at the time of injury. If the injury is more severe a
bump caused by the separated joint may be seen or felt at the
tip of the shoulder bones.
is often diagnosed quite readily from the history of the traumatic
event, along with physical examination findings. An x-ray should
be performed to ensure there is no fracture of these bones.
If the diagnosis is unclear, an x-ray taken while the patient
holds a weight in his or her hand may be helpful. When this
type of x-ray is taken, the force of the weight will exagerate
any shoulder joint instability and better show the deformity
of the separated shoulder.
Treatment of a separated
shoulder depends on the severity of the injury. The initial
treatment of a separated shoulder consists of controlling the
inflammation, and resting the joint. This can be done for the
first several days until the swelling around the joint has subsided.
Anti-inflammatory medication such as Advil or Motrin will also
help to minimize the pain and inflammation--check with your
doctor before using these medications. A sling to rest the shoulder
joint may be worn until the pain has subsided enough to begin
physical therapy exercises. Only in rare circumstances and severe
injuries will surgery be needed to correct an AC joint disruption.
AC Joint Arthritis
Arthritis of the
AC joint may be a source of significant pain. This condition
may result from previous injury, the natural "wear and
tear" that occurs with aging, or from other conditions.
As the joint wears out, the ends of the clavicle and acromion
bones may rub together, causing pain. Bone spurs may also develop,
causing pressure on the muscles underneath.
If this condition
becomes severe enough, a surgery may be necessary in order to
relieve the pain. The procedure usually involves removing the
distal end of the clavicle (about 1 cm of bone is removed).
This may be done directly through a small incision, or with
Figure 1. The
acromioclavicular (AC) joint may be felt at the end of the collar
Figure 2. An AC
joint separation. Normally the clavicle and the acromion line
up with one another. Note that in this picture they do not.
Figure 3. A bump
can be seen on this patient who has an AC joint separation.