Sometimes an injury causes a shoulder bone to completely or partially crack. The fracture usually involves your collarbone (clavicle) or the area just below the ball of your upper arm bone (humerus). The cause is rarely a surprise — you received a sudden blow to your shoulder or had a bad fall. Pain follows, and you may be able to see your shoulder bones out of position.

Fractures are either "displaced" or "nondisplaced."

• A displaced fracture is a bone fracture in which the pieces on either side of the break are out of line
• When the broken pieces line up on each side of the break, the fracture is called nondisplaced

Nearly 80% of all shoulder fractures are nondisplaced — the broken pieces remain in place while they heal. Fortunately, the broken pieces do not have to be perfectly aligned for them to heal properly or for your shoulder to function properly. Some degree of displacement may be acceptable for proper healing.

The remaining 20% are displaced — and may require surgery.

After a physical examination of your shoulder, your physician will confirm the diagnosis with an x-ray. This also will show the extent of the damage.

Your doctor will attempt to place your broken bones back into a position that will allow healing and help restore mobility. You may need to wear a sling to immobilize the area while it heals. Most fractures can be treated without surgery, and heal in about 3 to 4 months.

In some cases, your doctor may suggest further treatment, including surgery and physical therapy to help you restore shoulder function, strength, and mobility.

The choices in surgery are several and depend on the type of fracture.

Since most shoulder fractures are the nondisplaced type, you could recover good function in your shoulder. Since these injuries are treated with immobilization, however, you may develop a stiff or "frozen" shoulder.

Displaced fractures may require surgery in order to regain good function of the shoulder.