Summary Deltoid ruptures are very are injuries that generally occur secondary to massive rotator cuff tears, repeat corticosteroid injections into the deltoid, or acute trauma. Diagnosis is made clinically with depression over the deltoid in acute ruptures with deltoid strains and partial ruptures presenting with localized tenderness and ecchymosis. Treatment of partial tears is rest, NSAIDs and observation. Early surgical repair is indicated for complete tears. Epidemiology Incidence rare Risk factors repeated corticosteroid injections about the shoulder rotator cuff tear trauma Etiology Pathophysiology mechanism secondary to repeated corticosteroid injections about the shoulder massive rotator cuff tear proximal migration of the humeral head leads to compression/abrasion of undersurface of deltoid by greater tuberosity iatrogenic injury during open rotator cuff repair trauma sudden deltoid contracture shoulder contusion Associated conditions rotator cuff tear Anatomy Deltoid anatomy Presentation Symptoms shoulder pain Physical exam inspection depression over deltoid soft tissue mass distal to depression (contracted muscle) Imaging Radiographs recommended views shoulder radiographs findings associated with cuff tear arthropathy proximal humeral head migration Ultrasound indications noninvasive method of detection findings shows deltoid gap with intact surrounding fibers MRI indications differentiate partial vs complete deltoid tears associated rotator cuff pathology findings deltoid defect associated rotator cuff tear Treatment Nonoperative observation only indications chronic injuries in elderly patients Operative early surgical repair indications complete rupture deltoplasty with mobilization and anterior transfer of the middle third of the deltoid indications iatragenic injury during rotator cuff repair