Shoulder Instability

What is Shoulder Instability?

Shoulder instability occurs when the structures that normally keep your shoulder joint stable are compromised, allowing the upper arm bone (humerus) to move excessively within the shoulder socket (glenoid). This can range from subtle looseness that causes pain and dysfunction to complete dislocations where the joint comes completely apart.

The shoulder joint sacrifices stability for mobility, making it the most commonly dislocated joint in the body. Shoulder instability can be traumatic (resulting from injury) or atraumatic (developing gradually), and may involve anterior (forward), posterior (backward), or multidirectional instability patterns.

What Causes Shoulder Instability?

Shoulder instability develops through various mechanisms and contributing factors:

Traumatic causes:

  • Shoulder dislocations from falls, tackles, or direct impact

  • High-energy injuries during contact sports

  • Falls onto an outstretched arm with external rotation

  • Sudden forceful movements that exceed joint limits

  • Motor vehicle accidents or significant trauma

Overuse mechanisms:

  • Repetitive overhead activities stretching joint capsule over time

  • Swimming, particularly with poor technique

  • Throwing sports with excessive volume or poor mechanics

  • Gymnastics or activities requiring extreme range of motion

  • Gradual stretching of ligaments from repetitive stress

Anatomical factors:

  • Naturally shallow shoulder socket (glenoid dysplasia)

  • Loose joint capsule and ligaments (generalised joint hypermobility)

  • Labral tears that reduce socket depth

  • Previous shoulder surgery affecting normal anatomy

  • Congenital variations in bone or soft tissue structure

Contributing factors:

  • Muscle imbalances around the shoulder girdle

  • Weak rotator cuff muscles unable to provide dynamic stability

  • Poor scapular control and positioning

  • Postural stress leading to altered shoulder mechanics

  • Inadequate rehabilitation following previous injury

  • Fatigue during training or competition

What Are the Symptoms?

Shoulder instability presents with varying symptoms depending on the type and severity:

Primary symptoms:

  • Feeling of the shoulder "slipping" or "giving way"

  • Apprehension or fear when moving the arm in certain positions

  • Pain that may be vague and difficult to localise

  • Weakness in the affected arm, particularly with overhead activities

Activity-related symptoms:

  • Difficulty with overhead sports (swimming, tennis, throwing)

  • Pain and apprehension when reaching behind your back

  • Feeling of instability during sleep or when lying on the shoulder

  • Reduced performance in activities requiring shoulder stability

  • Compensatory movement patterns to avoid unstable positions

Recurrent instability symptoms:

  • Episodes of partial dislocation (subluxation) that reduce spontaneously

  • Increasing frequency of instability episodes over time

  • "Dead arm" sensation during throwing or overhead activities

  • Clicking, popping, or grinding sensations

  • Progressive loss of confidence in shoulder function

Functional limitations:

  • Avoidance of certain arm positions or activities

  • Reduced participation in sports or recreational activities

  • Impact on work tasks requiring overhead reach or lifting

  • Sleep disturbance due to fear of shoulder movement

  • Compensatory neck and upper back tension

Associated symptoms:

  • Numbness or tingling in the arm (if nerves are affected)

  • Muscle spasms around the shoulder

  • Chronic pain that may persist between episodes

  • Stiffness if movement is consistently avoided

Experiencing shoulder instability or recurrent dislocations? Our specialist team has extensive experience treating shoulder instability across all levels of sport, from recreational athletes to professional rugby players and UFC fighters. We provide comprehensive assessment, targeted strengthening programmes, and sport-specific rehabilitation to restore confidence and function while preventing future episodes.