Focused examination for shoulder instability including anterior, posterior, and multidirectional instability testing, apprehension signs, and hyperlaxity assessment.
Shoulder instability examination requires assessment of anterior, posterior, and inferior laxity. Examiners expect you to differentiate between laxity (asymptomatic translation) and instability (symptomatic), recognize the apprehension-relocation sequence, and identify multidirectional instability (MDI).
High-Yield Exam Summary
Laxity vs Instability:
Classification:
| Type | TUBS | AMBRI |
|---|---|---|
| Etiology | Traumatic | Atraumatic |
| Direction | Unilateral (anterior 95%) | Multidirectional |
| Lesion | Bankart | Bilateral capsular laxity |
| Treatment | Surgery (often) | Rehabilitation (first line), Inferior capsular shift |
Direction of Instability:
Look:
Generalized Hyperlaxity (Beighton Score):
| Test | Points |
|---|---|
| Passive little finger MCP extension greater than 90° (each hand) | 1 each |
| Passive thumb to forearm (each hand) | 1 each |
| Elbow hyperextension greater than 10° (each arm) | 1 each |
| Knee hyperextension greater than 10° (each leg) | 1 each |
| Palms flat on floor with knees straight | 1 |
| Total | 9 |
Score greater than 4/9 = generalized hyperlaxity (relevant for MDI)
Anterior instability
Apprehension (not just pain) - patient feels shoulder will dislocate, resists further movement
Anterior instability
Ability to detect true positives
Ability to exclude false positives
Confirm anterior instability
Relief of apprehension when posterior force applied
Anterior instability (relocation prevents subluxation)
Ability to detect true positives
Ability to exclude false positives
Confirm anterior instability
Return of apprehension or pain when force released
Anterior instability (highly specific)
Ability to detect true positives
Ability to exclude false positives
Anterior laxity
Increased anterior translation compared to opposite side
Anterior laxity (not necessarily instability)
Ability to detect true positives
Ability to exclude false positives
Quantify translation (anterior and posterior)
Graded translation: Grade I: Translation to glenoid rim. Grade II: Over rim with spontaneous reduction. Grade III: Over rim, stays dislocated
Direction and degree of laxity
Ability to detect true positives
Ability to exclude false positives
Posterior instability
Apprehension or pain as humeral head subluxates posteriorly
Posterior instability
Ability to detect true positives
Ability to exclude false positives
Posterior instability
Clunk as humeral head subluxates posteriorly, then reduces on returning to neutral
Posterior instability
Ability to detect true positives
Ability to exclude false positives
Posteroinferior instability
Pain and posterior clunk
Posteroinferior instability
Ability to detect true positives
Ability to exclude false positives
Inferior laxity
Sulcus (hollow) appears below acromion. Graded: I: less than 1cm. II: 1-2cm. III: greater than 2cm
Inferior laxity (positive in MDI)
Ability to detect true positives
Ability to exclude false positives
Rotator interval competency
Sulcus persists in external rotation (normally reduces)
Rotator interval incompetence (significant MDI)
Ability to detect true positives
Ability to exclude false positives
Inferior capsule laxity
Abduction greater than 105° with scapula stabilized
Inferior glenohumeral ligament laxity
Ability to detect true positives
Ability to exclude false positives
TUBS Pattern (Traumatic Anterior):
AMBRI Pattern (Atraumatic MDI):
Posterior Instability Pattern:
Apprehension is Key: The apprehension test is most sensitive and specific when it elicits APPREHENSION (feeling of impending dislocation), not just pain. Pain alone may be from other pathology (impingement, labral tear).
"22-year-old male rugby player with history of anterior shoulder dislocation 6 months ago. Now has recurrent 'giving way' of the shoulder."
| pattern | history | examination | laxity | treatment |
|---|---|---|---|---|
| Traumatic Anterior (TUBS) | Clear dislocation event | Apprehension +, Relocation + | Unilateral | Often surgical |
| MDI (AMBRI) | Atraumatic, gradual onset | Bilateral laxity, Sulcus + | Bilateral | Rehabilitation first |
| Posterior | May be voluntary or post-trauma | Jerk test +, Posterior apprehension + | May be bilateral | Rehab, surgery if fails |
| Voluntary | No true instability, psychological | Can voluntarily sublux | Variable | Avoid surgery, psychology |
High-Yield Exam Summary