A shoulder dislocation occurs when the head of the humerus (upper arm bone) is forced completely out of the glenoid socket. The shoulder is the most commonly dislocated joint in the body due to its wide range of motion and relative structural vulnerability.
A single traumatic dislocation causes significant soft tissue damage that substantially increases the risk of recurrence — particularly in young, active patients. The most common associated injuries are a Bankart lesion of the anteroinferior labrum and a Hill-Sachs impaction fracture of the humeral head. MRI after reduction is essential to characterize these injuries and guide the decision between conservative and surgical management.
Causes
Traumatic dislocation
Most dislocations result from a significant force applied to the arm — such as a fall on an outstretched hand, a collision during contact sports, or a direct blow to the shoulder. The vast majority (approximately 95%) are anterior dislocations, with the humeral head shifting forward out of the socket. Football, hockey, skiing, and motor vehicle accidents are common causes.
Posterior and inferior dislocations
Posterior dislocations are less common and can occur during seizures or electric shock when the internal rotator muscles overpower the external rotators — they are frequently missed on initial imaging. Inferior dislocations (luxatio erecta) are rare and typically caused by a hyperabduction injury with the arm forced overhead.
Symptoms
An acute dislocation produces immediate, severe shoulder pain, visible deformity, and complete inability to move the arm. The shoulder loses its normal rounded contour and may appear squared-off. Numbness or tingling down the arm may indicate involvement of the axillary nerve or brachial plexus — a finding requiring careful neurological assessment. Patients typically hold the arm in a protected position and resist any attempt at movement.
Diagnosis
Diagnosis is confirmed with X-rays to identify the direction of dislocation and rule out associated fractures — including a Hill-Sachs lesion on the humeral head and a bony Bankart lesion on the glenoid rim. After reduction, a dedicated shoulder MRI is essential for evaluating soft tissue damage — including labral tears, Bankart lesions, rotator cuff tears, and capsular injury — all of which significantly influence the risk of recurrence and determine the need for further treatment.
Dislocation classification
- Anterior dislocation: Humeral head displaced forward — the most common type (95%). Typically associated with a Bankart lesion and Hill-Sachs impaction fracture.
- Posterior dislocation: Humeral head displaced backward — less common and frequently missed on initial AP X-ray. Associated with a reverse Hill-Sachs lesion (McLaughlin lesion).
- Inferior dislocation (luxatio erecta): Humeral head displaced downward — rare and often associated with neurovascular injury requiring urgent assessment.
- First-time vs. recurrent dislocation: Younger patients have a significantly higher risk of recurrence after a first dislocation — up to 80–90% recurrence rate in patients under 20 without surgical stabilization.
Treatments
Treatment depends on dislocation type, patient age and activity level, and the presence of associated soft tissue or bony injuries.
Prompt reduction of the dislocation is the first priority — typically performed in the emergency setting under sedation or analgesia. Prompt reduction minimizes muscle spasm and the risk of neurovascular injury.
First-time dislocation in young and active patients
Surgery is often advised for young or active patients after a first-time traumatic dislocation — particularly when significant labral or capsular damage is present on MRI. Arthroscopic Bankart repair or capsulorrhaphy restores shoulder stability and significantly reduces the risk of recurrent dislocation. After surgery, a thorough physical therapy program is critical to healing and recovering function.
First-time dislocation in older or lower-demand patients
Older patients who do not require full shoulder stability for sports or high-level activities are often managed conservatively. The arm is immobilized in a sling followed by physical therapy to restore strength and range of motion. The risk of recurrence is lower in older patients, and the risk of concurrent rotator cuff tear — which increases with age — must be assessed on MRI.
Recurrent dislocations
Patients with recurrent instability typically benefit from surgical stabilization regardless of age. When significant glenoid bone loss is present, a Latarjet procedure — transferring a bone block to the front of the glenoid — reconstructs the bony defect and provides additional stability beyond soft tissue repair alone.
Get an MRI to Confirm Your Diagnosis
Before surgical planning or starting treatment, a clear MRI diagnosis ensures the right path forward. First Look MRI offers self-pay Shoulder MRI scans — no doctor's order or insurance required — at our locations in Georgia, Texas, and Colorado.