607 - Intramuscular Infraspinatus Cyst as a Cause of Chronic Refractory Shoulder Pain: A Case Report

Thursday, February 19, 2026

5:00 PM - 6:30 PM AST

Presenting Author(s)

JJ

Jasmin Johnson, MD

PGY-3 Resident Physician
MedStar Georgetown-NRH
Accokeek, Maryland, United States

Co-Author(s)

CS

Corey T. Spector, DO

Attending Physician
Montefiore Einstein
New York, New York, United States

Submitter(s)

JJ

Jasmin Johnson, MD

MedStar Georgetown-NRH
Accokeek, Maryland, United States

Case Diagnosis: Infraspinatus Intramuscular Cyst

Case Description: A 50-year-old female with a history of cervical radiculopathy s/p ACDF and arthroplasty C4-5, C5-6 and ACDF C6-7, left rotator cuff tendinopathy, and a partial infraspinatus tear presented with severe left shoulder and periscapular pain, worsened by overhead movements. Physical examination revealed restricted external rotation and forward flexion, positive impingement tests, and left shoulder weakness. Despite prior interventions including physical therapy, trigger point injections, glenohumeral corticosteroid injection, and a left subacromial space corticosteroid injection, the pain persisted for over three years. MRI of the left shoulder revealed a low-grade partial-thickness articular-sided tear of the supraspinatus and a moderate-grade partial-thickness intrasubstance tear of the infraspinatus, and a large intramuscular cyst. The patient subsequently underwent an ultrasound-guided aspiration of the left infraspinatus cyst and a corticosteroid injection, resulting in significantly decreased pain, improved range of motion, and resolution of weakness at 2-months follow-up.

Discussions: Periarticular cysts are a recognized source of shoulder pain. Paralarbal cysts, the most common type, usually result from glenoid labral tears secondary to trauma or overuse. Intramuscular cysts, though less common, are strongly associated with rotator cuff pathology. While often asymptomatic, they can be a significant source of pain. These cysts are identified via MRI, as their location within the substance of a rotator cuff muscle or sheath prohibits detection via palpation or arthroscopy. If unrecognized, these cysts may enlarge and cause chronic refractory pain, compressive neuropathy, weakness, and muscle atrophy.

Conclusions: Because intramuscular cysts are frequently asymptomatic and undetectable on exam, their diagnosis is often missed. However, in cases of persistent pain that is unresponsive to conventional rotator cuff management, further evaluation with an MRI is warranted. Early identification allows for timely and appropriate intervention. Ultrasound-guided aspiration can provide symptomatic relief and reduce the risk of complications that may subsequently lead to lasting functional impairments.