Dislocated Shoulder

The shoulder is the most mobile joint in the human body, allowing the arm to move through an exceptionally wide range of motion — reaching overhead, behind the back, and across the body. This mobility comes at a cost: the shoulder's ball-and-socket joint is inherently shallow and relies heavily on surrounding soft tissue for stability, which makes it the joint most prone to dislocation.

A dislocated shoulder occurs when the ball-shaped head of the upper arm bone (humerus) is forced out of the shoulder socket (glenoid), most often as a result of a fall, sporting collision, or traffic accident. It is an acute injury that requires prompt medical attention — both to relieve significant pain and to reduce the risk of damage to the surrounding nerves, blood vessels, and joint structures. While anyone can dislocate a shoulder, it is particularly common among teenagers, people in their twenties, and athletes involved in contact or overhead sports.

How the Shoulder Joint Works and Why It Dislocates

The shoulder joint (the glenohumeral joint) is a ball-and-socket joint, but unlike the hip, its socket is shallow. It is often compared to a golf ball resting on a tee rather than sitting deep within a cup. This shallow socket is what gives the shoulder its exceptional range of motion, but it means the joint depends heavily on surrounding soft tissue for stability:

• The labrum: A ring of cartilage around the rim of the socket that deepens it and helps hold the humeral head in place
• The joint capsule and ligaments: Fibrous tissue surrounding the joint that limits excessive movement
• The rotator cuff muscles: Four muscles that dynamically stabilise the joint and control shoulder movement

A dislocation occurs when a force, typically a fall onto an outstretched arm, a direct blow, or a sudden wrenching motion during sport pushes the bone out of its socket. In most cases, this same force also damages the labrum, capsule, or bone at the point of dislocation, which is why the injury often involves more than the joint simply “popping out.”

Types of Shoulder Dislocation

Anterior Dislocation

By far the most common type, accounting for the large majority of shoulder dislocations. The humeral head is forced forward and out of the socket, typically from a fall onto an outstretched arm or a blow to a raised, rotated arm. Most closely associated with labral tears (Bankart lesions) and a compression injury to the back of the humeral head (Hill-Sachs lesion).

Posterior Dislocation

Far less common. The humeral head is forced backward out of the socket, often associated with a seizure, electric shock, or a direct blow to the front of the shoulder. Can be more easily missed on initial assessment, as the shoulder may appear less obviously deformed than with an anterior dislocation.

Inferior Dislocation (Luxatio Erecta)

A rare type in which the arm is forced upward and the humeral head is displaced directly downward. Associated with a higher rate of nerve and blood vessel injury and needs prompt specialist assessment.

Subluxation

A partial dislocation in which the humeral head moves partly out of the socket but does not fully separate, sometimes returning to place on its own. Still represents a significant injury to the joint's stabilising structures and should be assessed in the same way as a full dislocation.

Symptoms of a Dislocated Shoulder

• Severe pain, often extending down the arm or toward the neck
• A visibly out-of-place, squared-off, or deformed shoulder
• Inability to move the shoulder joint, or a feeling that it is “stuck”
• Swelling or bruising around the joint
• Muscle spasm around the shoulder
• Numbness, tingling, or weakness in the arm or hand — which can indicate nerve involvement and should be assessed promptly
• A sensation of the joint being loose or unstable, in the case of a subluxation

Injuries That Often Accompany a Dislocation

A shoulder dislocation rarely damages the joint capsule alone. Understanding what else may be injured helps explain why imaging, careful assessment, and sometimes surgery are part of proper treatment — even after the joint has been successfully put back in place.

• Bankart lesion: A tear in the front part of the shoulder socket. It is common after a first-time shoulder dislocation and can cause the shoulder to keep becoming unstable.
• Hill-Sachs lesion: A small dent or fracture on the back of the upper arm bone caused when the shoulder dislocates. It is common after first-time dislocations and even more common with repeated dislocations.
• Rotator cuff tear: More common in patients over 40, and an important reason why shoulder function should be carefully reassessed after reduction in this age group
• Nerve injury: Most often affecting the axillary nerve, which can cause numbness over the shoulder or weakness lifting the arm; the large majority of cases recover, but nerve function should always be checked before and after reduction
• Fracture: A break in the humerus or the glenoid rim can occur alongside a dislocation, particularly from higher-energy injuries

Risk Factors for Shoulder Dislocation

• Age, it is the most common in the teens and twenties, particularly among athletes
• Participation in contact or collision sports (rugby, football, martial arts) or overhead sports (swimming, volleyball, throwing sports)
• A previous shoulder dislocation, the single strongest predictor of a future dislocation, since the injured tissue rarely heals back to its original strength
• Generalised joint hypermobility or connective tissue laxity
• Family history of shoulder instability
• A fall onto an outstretched arm, particularly in older adults, who may also sustain an associated fracture or rotator cuff tear

Recurrent Shoulder Instability: Why Young Athletes Are at Particular Risk

Recurrence deserves particular attention because it is common, and because the risk is highly age- and activity-dependent. In patients under 25 who return to contact or overhead sport, the risk of a further dislocation after non-surgical treatment alone is substantial — in some studies, more than half of young athletes managed without surgery experience another dislocation. This is largely because the torn labrum (Bankart lesion) that occurs with a first dislocation rarely heals back to its original strength on its own, leaving the joint's natural restraint permanently weakened.

Each further dislocation tends to cause additional damage to the labrum and bone, which is why the number of dislocations a person has had before treatment is one of the strongest predictors of how well surgery will work if it is eventually needed. For this reason, early surgical stabilisation after a first dislocation — rather than waiting for repeated instability — is increasingly considered for younger athletes who intend to return to higher-risk sports, and is associated with meaningfully lower rates of further dislocation compared with delaying surgery until after multiple episodes.

Older patients, particularly those over 40, tend to have a lower risk of recurrent dislocation, but a higher likelihood of an accompanying rotator cuff tear, which carries its own implications for treatment and recovery.

How a Dislocated Shoulder is Diagnosed

• Physical Examination: Assessment of the shoulder's appearance, range of motion, and tenderness, along with a check of circulation and nerve function in the arm and hand before any attempt at reduction.
• X-ray (Before Reduction): Confirms the direction of dislocation and identifies any associated fracture before the joint is put back into place, since this changes how reduction is safely performed.
• X-ray (After Reduction): Confirms that the joint has been successfully relocated and checks for injuries such as a Hill-Sachs lesion or bony Bankart fracture that may only become clearer once the joint is back in place.
• MRI: Used after the acute injury, particularly in younger patients or those considering surgery, to assess the labrum, joint capsule, and rotator cuff in detail — structures not visible on X-ray.
• CT Scan: Occasionally used to precisely measure bone loss at the socket or humeral head, which is an important factor in deciding whether a bone-augmenting procedure is needed if surgery is being considered.

Recovery and Rehabilitation

• Follow your sling and immobilisation guidance closely, even once pain has settled, to protect the healing tissue
• Begin physiotherapy as directed — early, guided motion and progressive strengthening of the rotator cuff are central to both recovery and reducing future risk
• Expect a staged return to activity — range of motion typically returns before full strength, and full return to contact or overhead sport usually takes several months
• Report any numbness, persistent weakness, or a feeling of the shoulder “giving way” to your care team promptly
• Discuss your individual risk of recurrence with your specialist, particularly if you are young, active in contact or overhead sports, or have already had more than one dislocation — this shapes whether surgery is recommended before returning to sport