(shoulder) arthritis is a common source of pain and disability that
affects up to 20% of the older population. Damage to the cartilage
surfaces of the glenohumeral joint (the shoulder's "ball-and-socket"
structure) is the primary cause of shoulder arthritis.
There are many treatment options for shoulder arthritis, ranging from
pain medications and exercises for mild cases, to surgical procedures
for severe cases. Treatment decisions are based upon the cause, the
symptoms and the severity of the patient's disease. Each year, over
10,000 shoulder replacement surgeries are performed in the United
States to relieve pain and improve function for shoulders that are
severely damaged by glenohumeral arthritis.
The shoulder is the most mobile joint in the human body with a complex
arrangement of structures working together to provide the movement
necessary for daily life. Unfortunately, this great mobility comes
at the expense of stability. Several bones and a network of soft
tissue (ligaments, tendons, and muscles), work together to
produce shoulder movement. They interact to keep the joint in place
while it moves through extreme ranges of motion. Each of these structures
makes an important contribution to shoulder movement and stability.
Certain work or sports activities can put great demands upon the shoulder,
and injury can occur when the limits of movement are exceeded and/or
the individual structures are overloaded.
What is the labrum and what does it do?
The labrum is a disk of cartilage on the glenoid,
or "socket" side of the shoulder joint. The labrum helps stabilize
the joint and acts as a "bumper" to limit excessive motion of the
humerus, the "ball" side of the shoulder joint. More
importantly, it holds the humerus securely to the glenoid, almost
as if suction were involved. Although the glenoid itself is a relatively
flat surface, the labrum's cuff-like contour gives the glenoid a more
concave shape. The secure but flexible fit of the humerus within
the glenoid permits the great range motion of the healthy shoulder.
What is glenohumeral joint arthritis?
Glenohumeral joint arthritis is caused by the destruction of the cartilage
layer covering the bones in the glenohumeral joint. This creates a
bone-on-bone environment, which encourages the body to produce osteophytes
(bone spurs). Friction between the humerus and the glenoid increases,
so the shoulder no longer moves smoothly or comfortably. As osteophytes
develop, motion is gradually lost. A number of conditions can lead
to the breakdown of cartilage surfaces:
- Wear and tear over time
- Trauma (such as a fracture or dislocation)
- A chronic (long-standing) inflammatory condition
(such as rheumatoid arthritis)
- Osteonecrosis (bone death caused by loss of blood
- Chronic rotator cuff tears in which the head of the humerus
(the upper bone in the arm) loses its proper position in the middle
of the glenoid (socket)
- Rare congenital and metabolic conditions
- Post-surgical changes that can be a result of over-tightening
during instability surgery
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