Shoulder Instability: Symptoms and Rehabilitation

Shoulder instability

Shoulder instability is a condition in which the humeral head exhibits excessive mobility relative to the scapular glenoid, with a tendency towards subluxation or dislocation. It represents a frequent problem, especially in young athletes: the shoulder is the most dislocated joint in the human body, with an incidence of 23-24 episodes per 100,000 inhabitants/year. In young males under 25, the prevalence rises to 2-3%.

Shoulder instability manifests with pain, a feeling of the “shoulder coming out,” apprehension during movements, and functional limitation. While recurrent dislocations often require surgical intervention (especially in young athletes), many forms of instability respond excellently to a structured program of physiotherapy and rotator cuff muscle strengthening.

Table of Contents

• Anatomy of Shoulder Stability
• Types of Instability
• Causes and Risk Factors
• Symptoms
• Diagnosis
• Conservative Treatment
• Surgical Treatment
• Frequently Asked Questions (FAQ)
• Frequently Asked Questions
• Sources and Scientific References

Anatomy of Shoulder Stability

The shoulder (glenohumeral joint) is designed for maximum mobility at the expense of stability. The humeral head is 3-4 times larger than the scapular glenoid — a frequent comparison is that of a golf ball on a tee.

Static (Passive) Stabilizers

• Glenoid labrum: a ring of fibrocartilage that deepens the glenoid by 50%, increasing the contact surface and creating a suction effect
• Glenohumeral ligaments (superior, middle, inferior): capsular reinforcements that limit translation in different positions. The inferior glenohumeral ligament (IGHL) is the most important, especially in abduction and external rotation
• Joint capsule: fibrous envelope surrounding the joint
• Intra-articular negative pressure: creates a “vacuum” effect that stabilizes the humeral head

Dynamic (Active) Stabilizers

• Rotator cuff: 4 muscles (supraspinatus, infraspinatus, subscapularis, teres minor) that “center” the humeral head in the glenoid during movement. The supraspinatus is the most frequently injured
• Long head of the biceps: depressor and anterior stabilizer of the humeral head
• Deltoid: main mover but also a stabilizer when the cuff is functional
• Scapulothoracic muscles (trapezius, serratus anterior, rhomboids): control the position of the scapula during arm movement (scapulohumeral rhythm)

Types of Instability

Classification by Direction

• Anterior (95% of cases): the humeral head moves forward and downward. It is the most common form, typical of traumatic dislocation
• Posterior (2-5%): less common, often misdiagnosed. Typical of epileptic seizures and electric shocks
• Inferior: rare as an isolated form
• Multidirectional (MDI): instability in more than one direction, typical of hyperlax patients (generalized joint hypermobility)

Classification by Cause

• Traumatic (TUBS: Traumatic, Unilateral, Bankart lesion, Surgery): a single traumatic event (fall, sports collision) causes the first dislocation, damaging the glenoid labrum (Bankart lesion) and/or the capsule. High recurrence in young people (up to 90% under 20 years old)
• Atraumatic (AMBRI: Atraumatic, Multidirectional, Bilateral, Rehabilitation, Inferior capsular shift): instability without significant trauma, often bilateral, in patients with constitutional hyperlaxity. Responds better to rehabilitation
• Micro-instability (acquired): developed gradually due to repeated microtrauma (overhead sports: volleyball, swimming, tennis, baseball). There are no frank dislocation episodes but pain, performance deficit, and a feeling of instability

Classification by Severity

Causes and Risk Factors

Causes

• Traumatic dislocation: fall on an abducted and externally rotated arm, sports collision. Causes a Bankart lesion (detachment of the anteroinferior glenoid labrum) and/or a Hill-Sachs lesion (impression on the humeral head)
• Congenital ligamentous hyperlaxity: constitutionally lax capsules and ligaments
• Repeated microtrauma: overhead sports with repetitive load on the joint (baseball, swimming, volleyball)
• Neuromuscular deficit: weakness of the rotator cuff and scapular stabilizers

Risk Factors for Recurrence

• Age < 25 years at first episode: recurrence rate of 80-90%
• Male sex: higher recurrence
• Contact sports: rugby, soccer, hockey, martial arts
• Bankart lesion: the glenoid labrum lesion reduces stability by 20%
• Bone defect (glenoid > 20% or engaging Hill-Sachs): high risk of recurrence even after surgery
• Generalized joint hyperlaxity: Beighton score ≥ 4/9

Symptoms

Acute Dislocation

• Intense and sudden pain in the shoulder
• Visible deformity: the shoulder appears “squared off” (epaulet sign) due to the dislocated humeral head
• Inability to move the arm
• The patient supports the arm with the opposite hand
• Possible associated injuries: axillary nerve (deltoid hypoesthesia), vascular injuries (rare)
• Requires manual reduction in the emergency room

Chronic Instability (between episodes)

• Apprehension: feeling of the “shoulder about to come out” in certain positions (typically abduction + external rotation — apprehension position)
• Pain: dull, deep, often anterior or posterolateral
• “Dead arm”: sudden episodes of weakness and sharp pain during athletic movements (throwing, serving)
• Functional instability: feeling of insecurity, avoidance of certain movements
• Reduced athletic performance
• Clicking or “shifting” sensation during movement

Diagnosis

Clinical Examination

• Anterior apprehension test: the arm is brought into 90° abduction and external rotation — positive if the patient feels fear/pain (sensitivity 72%, specificity 96%)
• Relocation test (Jobe’s relocation): from the apprehension position, posterior pressure on the humeral head reduces apprehension — sudden removal of pressure reproduces the symptom
• Anterior and posterior drawer test: translation of the humeral head forward and backward
• Sulcus sign: inferior traction of the arm — positive if a dimple appears below the acromion (inferior instability). A sulcus > 2 cm that does not reduce with external rotation suggests inferior capsular laxity (multidirectional instability)
• Beighton test: assessment of generalized hyperlaxity
• Rotator cuff evaluation: tests for the supraspinatus and other rotator cuff muscles

Imaging

• X-ray (AP, lateral, axillary): evaluation of fractures, Hill-Sachs lesions, bony Bankart, signs of osteoarthritis
• MRI (magnetic resonance imaging): evaluation of the glenoid labrum, rotator cuff, capsule. Arthro-MRI (with intra-articular contrast medium) is the gold standard for labral lesions (sensitivity 89-95%)
• CT scan: to quantify glenoid bone loss (important criterion for surgical choice) and Hill-Sachs lesions

Conservative Treatment

When It Is Indicated

• First episode of dislocation in patients > 30-35 years old (low risk of recurrence)
• Atraumatic/multidirectional instability (AMBRI): rehabilitation is the first-choice treatment
• Micro-instability in overhead athletes
• Subluxations without significant structural lesions
• Patients who do not participate in contact sports

Phase 1: Post-dislocation Immobilization (0-3 weeks)

• External rotation brace (15-20°): recent evidence suggests that immobilization in external rotation reduces the recurrence rate compared to the classic arm-at-side position (in internal rotation), because it brings the detached labrum closer to the glenoid
• Duration: 2-3 weeks (controversial — reduce if possible to avoid stiffness)
• Cryotherapy: 15 minutes, 4-5 times a day for the first few days
• Isometric contractions of the rotator cuff and deltoid even during immobilization

Phase 2: Mobility Recovery (3-6 weeks)

• Passive and active assisted mobilization: gradual recovery of elevation and external rotation
• Codman’s pendulum exercises: arm swings for joint decoaptation
• Isometric strengthening of the rotator cuff and scapular stabilizers
• Avoid the apprehension position (abduction + external rotation) in this phase

Phase 3: Muscle Strengthening (6-12 weeks)

This is the key phase of rehabilitation:

Rotator Cuff Strengthening

• External rotation with resistance band: elbow at side at 90°, externally rotate against the band. 3 sets of 15
• Internal rotation with resistance band: same setup, internally rotate. 3 sets of 15
• External rotation at 90° abduction: with resistance band or light dumbbell. 3 sets of 12
• Full can (elevation in the scapular plane with thumb up): 3 sets of 12

Scapular Stabilization

• Scapular retraction: bring shoulder blades together and down. 3 sets of 15
• Push-up plus: push-up with upward scapular protraction (serratus anterior strengthening). 3 sets of 12
• Resistance band row: pull the band towards the body, bringing the shoulder blades together. 3 sets of 12
• Y-T-W-L from prone: 2 sets of 8 for each position

Proprioception and Dynamic Stabilization

• Rhythmic stabilization: the physical therapist applies manual perturbations while the patient maintains the arm in different positions
• Closed-chain exercises: wall push-ups, floor push-ups — joint compression stabilizes the shoulder
• Ball on wall: roll a ball against the wall with the hand at different heights
• Exercises on unstable surfaces: push-ups on a fitball or Bosu

Phase 4: Return to Sport (12-24 weeks)

• Sport-specific re-athleticization: progressive athletic movements
• Graduated throwing program (for throwing sports)
• Plyometrics: explosive exercises for power restoration
• Kinesio taping: can be used as proprioceptive support during return to sport
• Return criteria: external rotation strength ≥ 85% of the healthy side, absence of apprehension, completion of the sport-specific program

Surgical Treatment

Indications

• Young athletes (< 25 years old) with a first episode of dislocation in contact sports: the recurrence rate is so high (80-90%) that early surgery is increasingly recommended
• Recurrent dislocations (2 or more episodes)
• Significant structural lesions: Bankart, SLAP, HAGL, bone defect
• Failure of rehabilitation after 6 months

Techniques

• Arthroscopic Bankart repair: reinsertion of the glenoid labrum with suture anchors. It is the standard for anterior instability. Success rate: 85-92%
• Latarjet (coracoid transfer): the coracoid with the conjoint tendon is transferred to the anterior glenoid. Indicated when there is glenoid bone loss > 20% or engaging Hill-Sachs. Success rate: 95-98%
• Remplissage: filling of the Hill-Sachs defect with capsule and infraspinatus. Can be combined with Bankart
• Capsular plication: reduction of capsular volume — indicated in multidirectional instability
• Shoulder prosthesis: in rare cases of chronic instability arthropathy with severe osteoarthritis

Post-surgical Rehabilitation

Rehabilitation after instability surgery requires 4-6 months:

• 0-4 weeks: immobilization in brace, isometric contractions
• 4-8 weeks: gradual recovery of passive mobility
• 8-12 weeks: active mobility and light isometric/isotonic strengthening
• 12-16 weeks: progressive strengthening of the rotator cuff and scapular stabilizers
• 4-6 months: return to sport (6-9 months for contact sports)

Frequently Asked Questions (FAQ)

Frequently Asked Questions

What are the common symptoms indicating potential shoulder instability?

Individuals with shoulder instability may experience pain, a sensation of the shoulder “coming out” or feeling loose, and apprehension when moving the arm into certain positions. These symptoms can range from acute and severe after a dislocation to more chronic and subtle with recurrent instability.

How is shoulder instability typically diagnosed?

Diagnosis usually involves a thorough clinical examination by a healthcare professional, assessing the range of motion, stability, and specific provocative tests. Imaging studies, such as X-rays or MRI, may also be utilized to confirm the diagnosis and identify any associated structural damage.

What is the primary goal of rehabilitation for shoulder instability?

The main objective of rehabilitation is to restore optimal shoulder stability and function. This involves strengthening the dynamic stabilizers, improving proprioception, and regaining full range of motion under the guidance of a physical therapist.

Can shoulder instability develop without a specific traumatic injury?

Yes, shoulder instability can develop atraumatically, meaning without a direct traumatic event. This form often relates to generalized ligamentous laxity or repetitive microtrauma, contrasting with traumatic instability which typically follows a distinct injury like a fall or direct blow.

For a broader overview of related conditions, see our complete guide to shoulder pain.

Sources and Scientific References

1. Stokes DJ et al. (2023). Physical Therapy for the Treatment of Shoulder Instability. Phys Med Rehabil Clin N Am. 34:393-408. DOI | PubMed
2. Hayes K et al. (2002). Shoulder instability: management and rehabilitation. J Orthop Sports Phys Ther. 32:497-509. DOI | PubMed
3. Jaggi A et al. (2010). Rehabilitation for shoulder instability. Br J Sports Med. 44:333-40. DOI | PubMed
4. Klintberg IH et al. (2015). Consensus for physiotherapy for shoulder pain. Int Orthop. 39:715-20. DOI | PubMed
5. Green S et al. (2003). Physiotherapy interventions for shoulder pain. Cochrane Database Syst Rev. 2003:CD004258. DOI | PubMed