Shoulder Instability & Dislocation — What Does It Actually Mean?

Shoulder instability is often described as a shoulder that “comes out”.

However, instability is broader than this.

Some people experience a complete dislocation. Others experience a subluxation, where the joint partially slips out and then returns to position. Some people do not experience another episode of either, but continue to feel apprehensive, vulnerable or unable to trust the shoulder in particular positions.

When someone reports that their shoulder feels unstable, it is important to understand what unstable means to them.

Does the shoulder actually move out of the joint? Does it feel as though it might? Does the arm suddenly feel weak or lose control? Is there a particular position that no longer feels safe? Or are certain movements being avoided because of the memory of the original injury?

These are different problems and may require different approaches to management.

1. Why can the shoulder become unstable?

The shoulder is a ball-and-socket joint, but the socket is relatively shallow. This allows a very large range of movement and enables activities such as reaching overhead, throwing, lifting, climbing and tackling.

Shoulder stability is not provided by one structure alone.

It depends on an interaction between the:

• shape of the joint
• labrum
• capsule and ligaments
• muscles around the shoulder
• nervous system and movement control
• demands placed on the shoulder

Following a traumatic dislocation, some of these structures may be injured and the way the muscles control the shoulder may also change.

This is why shoulder instability should not be viewed simply as a problem of “loose tissues”.

A shoulder can show structural changes on imaging and still function very well. Another person may have relatively modest structural findings but continue to experience significant apprehension, loss of control or recurrent instability.

Assessment therefore needs to consider the person and the shoulder, not simply the MRI.

2. Dislocation, subluxation and apprehension are not the same thing

Dislocation

A shoulder dislocation occurs when the humeral head — the ball at the top of the upper arm — completely loses contact with the socket.

Most traumatic shoulder dislocations occur anteriorly, where the humeral head moves forwards out of the joint, although instability can occur in other directions.

A traumatic shoulder dislocation usually requires reduction — placing the joint back into position — by an appropriately trained healthcare professional.

Subluxation

A subluxation is different.

The humeral head partially loses its normal relationship with the socket but does not remain completely dislocated.

People often describe this as:

“It slipped.”   “It went out and came straight back.”   “It shifted.”

These episodes are still clinically important and may form part of recurrent shoulder instability.

Apprehension

Apprehension is different again.

The shoulder may not actually move out of the socket at all.

Instead, a particular position creates a feeling of vulnerability, threat or impending instability.

People often describe:

“It feels like it's going to come out.”

That experience is important. Apprehension can influence movement, confidence and return to activity even when another dislocation has not occurred.

3. What gets injured when a shoulder dislocates?

A traumatic anterior shoulder dislocation can injure several structures. Three findings commonly discussed following imaging are a Bankart lesion, a bony Bankart lesion and a Hill-Sachs lesion.

Bankart Lesion

An injury to the labrum at the front of the socket, commonly associated with traumatic anterior shoulder dislocation.

Bony Bankart Lesion

An injury involving bone from the front edge of the glenoid as well as the labral region.

Hill-Sachs Lesion

An impression injury to the humeral head that can occur as it impacts against the edge of the socket during a dislocation.

Other injuries can also occur, including fractures, rotator cuff injury and nerve injury. The likelihood of associated injury varies according to age and injury mechanism.

It is important to recognise that:

Finding a Bankart or Hill-Sachs lesion does not automatically mean surgery is required.

Imaging helps describe the injury and contributes to decision making.

The scan informs the decision, but it should not determine the decision in isolation.

4. Will the shoulder dislocate again?

This is one of the most common concerns following a first shoulder dislocation.

There is no single recurrence percentage that applies to everyone.

A 2015 systematic review and meta-analysis by Olds and colleagues found recurrent instability in approximately 39% of adults following a first-time traumatic anterior shoulder dislocation across the included studies.¹

However, this average hides considerable variation between individuals.

In that review, recurrence was substantially more likely in younger people, men and people with hyperlaxity, while a greater tuberosity fracture was associated with a substantially lower risk of recurrence.¹

More recent research has reinforced the same important message: recurrence is multifactorial. Age, sex, activity, injury characteristics and other patient-related factors contribute to recurrence risk, but no single factor can perfectly predict what will happen to an individual.²

The PRIS — Predict Recurrent Instability of the Shoulder — model was developed by Dr Margie Olds and colleagues to help estimate recurrence risk following a first traumatic anterior shoulder dislocation.³

PRIS was developed from a prospective New Zealand cohort of people aged 16–40 years. It combines several pieces of information rather than attempting to predict recurrence from a single characteristic.³

The variables within the model include:

• age
• bony Bankart lesion
• shoulder pain and disability
• fear of reinjury
• whether the dominant or non-dominant shoulder was injured
• immobilisation following the original injury

These are prediction variables and should not automatically be interpreted as causes.

For example, immobilisation was associated with recurrence within the prediction model. This does not establish that wearing a sling prevents another dislocation.

PRIS is also more useful for helping identify people at relatively low risk of recurrence than for confidently predicting exactly who will redislocate.

Recurrence risk can be estimated, but future instability cannot be predicted with certainty.

Access the PRIS tool →

5. Why does instability sometimes continue?

It is tempting to think that recurrent instability simply means:

“The damaged tissues did not heal.”

Structural injury can be important, but instability is more complex than this.

A useful framework is to consider four areas:

CONTROL • CAPACITY • CONFIDENCE • DEMAND

CONTROL

Can the shoulder be controlled in the positions that are required?

After injury, muscle activation and coordination can change. Rehabilitation should progressively restore control through increasingly challenging positions, including positions that initially feel vulnerable.

CAPACITY

Does the shoulder have sufficient strength, endurance and power?

Performance on a single strength test is not enough.

The shoulder needs sufficient physical capacity for the activity being undertaken — whether that is lifting at work, throwing a ball, tackling another player, controlling a horse or managing everyday activity.

CONFIDENCE

Does the person trust the shoulder?

Fear of reinjury, kinesiophobia and apprehension are increasingly recognised as important components of shoulder instability and recovery. A systematic review found associations between these psychological factors and pain, function, quality of life and return to sport.⁴

A person may regain strength and movement but still avoid the position in which the original injury occurred.

Confidence is not restored simply through reassurance.

It may need to be rebuilt through progressive exposure to meaningful movement and repeated successful experiences.

DEMAND

What does the shoulder need to do?

This is an important component that is often overlooked.

A shoulder that is fully capable of everyday activity may not yet be prepared for rugby, climbing, skiing, throwing, horse riding, heavy manual work or another high-demand activity.

The important question is not simply:

“Is the shoulder strong?”

It is:

“Do Control, Capacity and Confidence match the Demand?”

6. Why self-management and rehabilitation matter

Rehabilitation following shoulder instability should not simply follow the sequence:

wait → regain movement → strengthen the rotator cuff → return to activity.

Good rehabilitation progressively restores the capabilities required by the individual.

Early rehabilitation may focus on comfortable movement, muscle activation and restoring control. As recovery progresses, rehabilitation should increasingly address strength, endurance, power, reactive control, confidence and the specific demands of the activities being returned to.⁵

Rehabilitation should therefore become increasingly individualised.

A rugby player's programme should eventually look different from a swimmer's.

A climber's rehabilitation should differ from that of a horse rider.

And someone aiming to comfortably lift their children does not require the same rehabilitation programme as an international athlete.

Build Capacity Before Chaos.

The more unpredictable and demanding elements of activity can then be introduced progressively.

Read more: Rehabilitation after Shoulder Dislocation →

7. How is readiness to return to sport assessed?

Time matters after injury, but time alone does not indicate whether the shoulder is ready.

Return-to-sport testing after shoulder instability is still evolving, and there is currently no universally accepted single test or test battery that can declare an athlete “ready”.⁶

Instead, readiness should be assessed by building a broader picture of the individual and determining whether the shoulder is prepared for the demands of the activity.

This may include assessment of:

• range of movement
• strength
• endurance
• power
• reactive control
• sport-specific performance
• apprehension
• confidence and psychological readiness

Capability should then be matched to the demands of the activity.

Read more: Return to Sport After Shoulder Injury →

8. When should further assessment be considered?

Further assessment is particularly important if the shoulder:

• repeatedly dislocates or subluxes
• continues to feel as though it may come out
• remains significantly weak
• has persistent numbness or altered sensation
• has significant ongoing loss of movement
• remains painful
• prevents a return to work or sport
• feels physically recovered but still cannot be trusted

For people returning to higher-demand sport or work, assessment should go beyond determining whether the shoulder is pain-free.

The key question is whether the shoulder is ready for the demands that will be placed on it.

When should further advice be sought? →

The key message

A shoulder dislocation is an injury.

Shoulder instability is broader than the injury itself.

It can involve structural injury, altered control, reduced physical capacity, recurrent instability episodes, apprehension, fear and loss of confidence.

Successful management therefore involves more than simply waiting for tissue healing or making the shoulder stronger.

It requires consideration of the individual, the shoulder and the activity they want to return to.

CONTROL • CAPACITY • CONFIDENCE • DEMAND

Look for the gaps.

About Dr Margie Olds

Dr Margie Olds, PhD is a shoulder physiotherapist and researcher specialising in shoulder instability, recurrence risk and return to sport. Her research includes the development of the Predict Recurrent Instability of the Shoulder (PRIS) model and research into recurrence risk, rehabilitation and psychological factors following shoulder instability.

References

1. Olds M, Ellis R, Donaldson K, Parmar P, Kersten P. Risk factors which predispose first-time traumatic anterior shoulder dislocations to recurrent instability in adults: a systematic review and meta-analysis. Br J Sports Med. 2015;49(14):913-922.
2. Makaram NS, Becher H, Oag E, et al. Predicting recurrence of instability after a primary traumatic anterior shoulder dislocation. Bone Joint J. 2024;106-B(10):1111-1117.
3. Olds MK, Ellis R, Parmar P, Kersten P. Who will redislocate his/her shoulder? Predicting recurrent instability following a first traumatic anterior shoulder dislocation. BMJ Open Sport Exerc Med. 2019;5(1):e000447.
4. Brindisino F, Garzonio F, Di Giacomo G, Pellegrino R, Olds M, Ristori D. Depression, fear of re-injury and kinesiophobia resulted in worse pain, quality of life, function and level of return to sport in patients with shoulder instability: a systematic review. J Sports Med Phys Fitness. 2023;63(4):598-607.
5. Olds M, Uhl TL. Current clinical concepts: nonoperative management of shoulder instability. J Athl Train.
6. Myers H, Wulff K, Antonelli C, et al. Objective measures for assessing readiness to return to sport after shoulder instability procedures are not standardized: a systematic review. Arthrosc Sports Med Rehabil. 2024;6(5):100978.

This information is intended as general education and does not replace individual medical or physiotherapy assessment.