Shoulder dislocation is a common injury in which the upper arm bone pops out of its usual spot in the shoulder joint. The shoulder is built to move in many directions, which can make it easier for the joint to slip out of place, especially from a fall or other impact. Dislocated shoulders are very painful and make it hard to move the arm. With prompt treatment, most people recover well in a few weeks. Physical therapy, bracing, or occasionally surgery can help the shoulder heal and prevent future injuries.

In a shoulder dislocation, the ball-shaped top of the upper arm bone (humeral head) comes out of the socket (glenoid) in the shoulder blade (scapula). Of all the joints in the body, the shoulder has the greatest range of motion, with a large humeral head and a shallow socket, similar to a golf ball on a tee. However, the increased shoulder movement also makes it the least stable and the most likely joint to pop out of place.

Several structures help stabilize the shoulder joint. A “bumper cushion” cartilage rim called the labrum deepens the socket to help with stability. Ligaments connect the bones to each other and reduce excessive motion. A set of muscles called the rotator cuff surrounds the joint to hold the head in place. When a shoulder dislocates, these structures stretch, tear, and lose their stabilizing function, making future dislocations more likely.

There are two levels of dislocation:

• Partial dislocation (also called subluxation): the ball partly comes out of the socket and sometimes relocates without assistance.
• Complete dislocation: the ball leaves the socket entirely, and stays out until physically put back in place.

Most shoulder dislocations are “anterior,” which means the head moves forward and out of the socket. Less often, the head moves backward (“posterior”) or downward (“inferior”).

A dislocated shoulder can result from falls, sports injuries, and car accidents or other strong forces that push, pull, or twist the arm and cause the ball of the upper arm bone to slip out of the socket. For example, falling on an outstretched arm or being struck during contact sports can lead to shoulder dislocation.

Violent muscle contractions during a seizure or an electric shock can cause the shoulder to dislocate out the back. In rare cases, the shoulder can dislocate downward if the arm is forcefully pulled above the head.

Certain activities, injuries, and body traits increase the likelihood of a dislocated shoulder. Active teens and young adults have a higher chance of shoulder dislocation. Boys and young men sustain about 70 percent of shoulder dislocations overall. Older adults who fall may also sustain shoulder dislocations that are often accompanied by severe rotator cuff tears and fractures.

Key risk factors include:

• Playing contact sports, such as football, basketball, or hockey, because of frequent falls and collisions
• Taking part in activities with a high chance of falling, such as cycling, skiing, or gymnastics
• Having a previous shoulder dislocation, especially if the supporting tissues did not heal fully, or a dedicated rehabilitation program was not followed
• Having naturally looser ligaments or joints, sometimes referred to as being “double jointed”
• Experiencing violent muscle contractions during seizures or electric shocks, which can cause the shoulder to dislocate

Most symptoms with a dislocated shoulder appear immediately after the injury. Main symptoms include:

• Severe pain in the shoulder, which often starts right after the injury and may worsen with movement or muscle spasms
• A visible change in the shape of the shoulder, such as a bump in the front or a flattening of the outer area, that makes it appear out of place or distorted
• Swelling around the joint that develops soon after injury
• Bruising near the shoulder or upper arm, usually appearing within hours or days
• Difficulty moving the arm, particularly when trying to lift it to the side
• Numbness or tingling in the shoulder, arm, or hand, which may signal that the nerves around the shoulder are being stretched
• Weakness and difficulty in lifting or rotating the arm
• Muscle spasms around the shoulder, which can increase pain and discomfort

In some cases, especially with partial dislocations, the symptoms may be brief and milder, and the joint may appear normal after the bones slip back into place. However, pain and a sense of instability can still be present.

To diagnose a dislocated shoulder, a doctor typically reviews the person’s medical history, with special attention to how the injury happened, what symptoms are present, and whether the shoulder has been dislocated before. Next, the doctor performs a shoulder examination, and orders one or more imaging tests.

During the physical exam, the doctor will look for signs of deformity, swelling, and tenderness. They will check the skin color and temperature of the arm and hand to make sure blood flow is normal. The doctor will also test for numbness or weakness to see if any nerves are affected.

Imaging tests help confirm the diagnosis, check for other injuries, and inform surgical planning, if necessary. Common tests include:

• X-ray to confirm joint position and detect fractures and prior conditions
• Magnetic resonance imaging (MRI) scan to detect tears in the labrum, ligaments, and rotator cuff
• Computed tomography (CT) scan to clarify bony details when a fracture is suspected or X-rays are inconclusive

Treatment for a dislocated shoulder focuses on returning the joint to proper alignment (also known as reduction) as well as controlling pain and swelling. Ongoing care includes rebuilding strength before returning to usual activities.

Anyone who suspects a shoulder dislocation should seek medical treatment immediately. Attempting a shoulder reduction by oneself, without proper setup and support, increases the risk of further damage.

Main treatments for shoulder dislocation include:

• Pain medications and sedation to reduce discomfort
• Closed reduction, in which a clinician guides the humeral head back into the socket
• Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or naproxen and pain relievers like acetaminophen (Tylenol) after reduction, to help ease the pain and swelling
• Ice or cold packs applied several times a day after reduction to reduce swelling (never place ice directly on bare skin)
• Immobilization with a sling or other device to protect the joint during early healing
• Follow-up with an orthopaedic shoulder specialist within several days after the reduction to assess the condition of the shoulder, rule out other injuries, arrange for additional testing if needed, and plan for treatment to help with recovery
• Possible surgery to repair torn cartilage (Bankart repair) or reconstruct damaged bone, in cases of complex or recurrent injuries
• Physical therapy, beginning with gentle motion, to strengthen the shoulder, restore function, and reduce the risk of repeat injury
• Additional follow-up care to monitor recovery and plan for a safe return to activities

For young people with first-time dislocations, especially athletes, surgery to repair the labrum and stabilize the shoulder can lower the risk of future dislocations compared to physical therapy alone. Most people recover well with these treatments, but some may need extra support, such as a brace, to protect the shoulder during certain activities.

A dislocated shoulder can lead to complications, especially if not treated promptly or if there is severe injury. Complications can also occur while trying to put the bone back into the joint. The main complications of a dislocated shoulder include:

• Nerve injury, especially to the axillary nerve, which can cause numbness or weakness in the shoulder or arm
• Blood vessel damage, which may lead to poor blood flow, a cool or pale hand, or swelling
• Tears of ligaments, tendons, or the labrum “bumper cushion” around the socket, all of which can cause ongoing pain or make the shoulder less stable
• Fractures of the upper arm bone or the socket, which may require surgery
• Rotator cuff tears, leading to weakness or trouble lifting the arm, especially in people over 40
• Recurrent dislocations, with the shoulder becoming increasingly unstable and more prone to come out of the socket, often due to stretched or damaged tissues
• Stiffness or loss of motion in the shoulder, sometimes called “frozen shoulder,” if the joint is not moved during recovery

If there is sudden numbness, weakness, color change, severe pain, or loss of pulse in the arm after a dislocation, it is important to seek emergency care right away. To diagnose damage to blood vessels, doctors may order CT angiography and recommend vascular surgery.

The outlook for people with a dislocated shoulder depends on factors such as age, the type of injury, and whether there is damage to other structures in the shoulder. Most people with a dislocated shoulder recover well, especially with prompt and proper treatment. Many return to their usual activities, including sports, after a period of healing and rehabilitation.

Younger, active people have a higher chance of the shoulder dislocating again. Although older adults have a lower risk of repeat dislocations, they are more likely to have associated injuries, such as rotator cuff tears or fractures.

Keeping the shoulder muscles strong and following a rehabilitation program can improve long-term results and reduce the risk of future problems. Regular follow-up with a doctor helps ensure the shoulder heals properly and stays stable over time.

“At Yale Medicine, we take a patient-centered team approach to shoulder instability treatment,” says Jim Hsu, MD, a Yale Medicine orthopaedic sports medicine surgeon who specializes in minimally invasive shoulder, knee, and elbow surgery. “Our experienced orthopaedic sports medicine specialists evaluate the shoulder, order advanced imaging, diagnose the condition and its multiple associated injuries, and offer the latest in evidence-based treatment carefully tailored to the individual patient, ranging from rehabilitation to arthroscopic and minimally invasive surgery. Comprehensive care is coordinated between sports medicine shoulder specialists, physical therapists, and athletic trainers to ensure that patients receive state-of-the-art care to help them reach their specific goals.”