HISTORY: 21 year old Hispanic male volleyball player who presents with persistent right shoulder pain × 7-8 weeks. Patient reports increased right shoulder pain when spiking the volleyball at the peak of his swinging motion. Otherwise, with everyday movements his shoulder does not bother him. He has been receiving local heat, electrical stimulation, rotator cuff strengthening exercises, and NSAID's. However, overall his right shoulder symptoms are unchanged. The patient also reports decreased ROM of right shoulder in abduction. He denies any numbness or tingling, denies any recent trauma. PHYSICAL EXAMINATION: On general examination in the training room, the patient is a muscular Hispanic male, looks stated age, in no acute distress. Musculoskeletal exam revealed no atrophy and 5/5 motor strength symmetrically throughout all 4 extremities. Moderate amount of pain on internal rotation of right shoulder, mild right scapular winging. Multiple trigger points appreciated on the anterior and middle deltoids. Anterior and posterior drawer tests on bilateral shoulders did not reveal any increased laxity. Reflexes revealed 2/4 MSR symmetrically throughout all 4 extremities. Sensation was intact to light touch and pin prick in bilateral upper extremities. Range of motion revealed 170° of right shoulder abduction and otherwise ROM of bilateral upper extremities was WNL. Provocative tests found Spurling's negative bilaterally, impingement sign right shoulder equivocal at 160°. Initially treated conservatively with NSAID's, moist heat, electrical stimulation, and strengthening exercises without any change in symptoms. Then 2% Lidocaine injected into right deltoid trigger points again with no effect. DIFFERENTIAL DIAGNOSIS: Right shoulder labral tear Right rotator cuff pathology Right shoulder instability Right humeral fracture Myofascial right shoulder pain TESTS AND RESULTS: Right shoulder pain films: large radiolucent lesion in metaphysis of right humerus. Right shoulder MRI: large unicameral cyst of proximal right humerus, 70-80% of entire humeral circumference. FINAL/WORKING DIAGNOSIS: Unicameral bone cyst of proximal right humerus; pain secondary to microfractures of cyst wall. TREATMENT: Surgical consultation Open currettage, methylprednisone injection, then iliac crest bone graft