Shoulder instability
What is shoulder instability?
Shoulder instability occurs when the humeral head does not remain reliably centred in the glenoid (socket). It may present as a complete dislocation, a partial dislocation (subluxation) or repeated episodes of apprehension and slipping.
Instability may follow a traumatic sporting injury, fall or collision. It can also occur in patients with ligament laxity, repetitive overhead loading, bone loss, or previous dislocations that have stretched or damaged the stabilising structures of the shoulder.
Anterior Instability
Anterior instability is the most common pattern. The humeral head slips forwards, often after an injury with the arm abducted and externally rotated. It may cause a Bankart lesion, Hill-Sachs lesion, capsulolabral injury or glenoid bone loss. Patients often feel apprehensive in throwing, tackling, swimming, overhead sport or gym positions that place the shoulder into external rotation.
Posterior Instability
Posterior instability occurs when the humeral head slips backwards. It can follow trauma or seizures, but it may also develop more subtly in athletes who load the shoulder in flexion and internal rotation, such as contact athletes, weightlifters, rowers and swimmers. Posterior instability is commonly under-recognised because symptoms may be pain, clicking or loss of power rather than an obvious dislocation.
Diagnosis and imaging
Diagnosis requires a detailed history of the first episode, direction of instability, number of dislocations, sporting demands and whether the shoulder reduces spontaneously. Examination assesses anterior and posterior apprehension, load-and-shift, sulcus sign, rotator cuff strength, scapular control and generalised laxity. X-rays assess joint position and bony injury. MRI or MR arthrogram assesses the labrum, capsule and associated soft-tissue injury. CT is particularly useful when recurrent instability, glenoid bone loss, Hill-Sachs lesions or posterior glenoid deficiency need precise assessment for surgical planning.
Non-surgical treatment
Non-surgical treatment is appropriate for selected first-time dislocations, lower-risk patients and instability driven mainly by muscle control or laxity. Rehabilitation focuses on rotator cuff strength, scapular mechanics, proprioception, kinetic-chain control and sport-specific confidence. The plan differs for anterior and posterior instability because the provocative positions and stabilising demands are not the same.
The right approach depends on age, sport, occupation, the number of instability episodes, direction of instability, imaging findings and the level of confidence the patient needs in the shoulder.
Surgical treatment
Surgery may be considered when instability recurs, when the shoulder remains unreliable despite rehabilitation, or when imaging shows injuries that carry a higher risk of further dislocation. Young contact athletes and high-demand patients often have a higher risk of recurrence after a traumatic dislocation.
The surgical plan is tailored to the pattern of instability. Options may include arthroscopic labral repair and capsular tightening, or bone-block procedures when there is significant glenoid bone loss or a high-risk instability pattern.
Surgery is considered for recurrent dislocation, persistent apprehension, high-risk athletes, significant labral or bony injury or failed rehabilitation. Anterior instability may be treated with arthroscopic Bankart repair, remplissage, or bone-block procedures such as Latarjet. Posterior instability may require posterior labral repair, capsular shift or treatment of posterior glenoid bone loss with a bone block procedure in selected cases. The aim is to match the operation to the direction of instability, tissue quality, bone anatomy and patient goals.
Recovery and follow-up
Recovery is staged. Early rehabilitation protects the repair or injured tissues, then restores range of motion, cuff control, scapular strength and sport-specific loading.
Return to contact sport, throwing, swimming or heavy gym work requires stable motion, strength symmetry, confidence and a clear understanding of risk positions. Recurrent instability, stiffness and persistent apprehension are monitored during follow-up.
Shoulder instability FAQs
What is the difference between anterior and posterior shoulder instability?
Anterior instability means the shoulder slips forwards, usually in abduction and external rotation. Posterior instability means it slips backwards, often with pushing, bench press, flexion and internal rotation. The diagnosis matters because treatment and rehabilitation are direction-specific
Does every shoulder dislocation need surgery?
No. Some first-time dislocations can be managed with a period of protection followed by structured physiotherapy. Surgery is more likely to be considered when instability recurs, when there is significant structural damage, or when the risk of recurrence is high because of age, sport or activity demands.
What imaging is needed for shoulder instability?
X-rays are used to assess alignment and look for fractures or bone defects. MRI or MR arthrogram can assess the labrum, capsule and soft tissues. CT may be used when glenoid bone loss or a more complex instability pattern is suspected.
Can physiotherapy fix shoulder instability?
Physiotherapy can be very effective for selected patients, especially when instability is non-traumatic, related to muscle control or a first-time event. Recurrent traumatic instability, significant labral injury or bone loss may be less likely to settle with physiotherapy alone.
When can I return to sport?
Return to sport depends on the type of instability, whether surgery is required and the demands of the sport. It is usually staged, with progression based on pain, movement, strength, control and confidence rather than time alone.
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