Muscle Weakness After Anterior Shoulder Dislocation

Primary Muscles Affected

The infraspinatus and teres minor demonstrate significant weakness and atrophy following anterior shoulder dislocation, creating a muscular imbalance where the anterior structures are relatively stronger than the weakened posterior external rotators 1
The supraspinatus commonly shows weakness and atrophy after anterior dislocation, with physical examination revealing focal weakness with decreased range of motion during abduction with external or internal rotation 1
Scapular stabilizer muscles demonstrate weakness and contribute to ongoing instability, with scapular dyskinesis compounding the problem by failing to maintain proper humeral head positioning 2

Weakened posterior shoulder musculature combined with overdeveloped or relatively stronger anterior musculature creates the biomechanical environment for anterior instability 1
The posterior rotator cuff experiences repetitive eccentric stress during activities, leading to fatigue and injury 1
This muscular imbalance prevents the humeral head from staying centered in the glenoid fossa during arm motion, perpetuating instability 1, 2

Younger patients are more likely to have labroligamentous injury and persistent instability after dislocation, demonstrating weakness in rotator cuff muscles combined with ligamentous laxity as the primary pathology 2, 3, 4
Older patients are more likely to have associated rotator cuff tears in addition to weakness, presenting with persistent pain and disability from combined rotator cuff pathology and nerve injuries 3, 4

Pain during external rotation maneuvers is a common finding in patients with anterior shoulder dislocation 1

Strengthening must target the external rotators, supraspinatus, and scapular stabilizers to restore the transverse force couple balance, with a focus on re-establishing proper shoulder and spine mechanics while restoring full range of motion 1