Supraspinatus

(M1.AN.17.4719) A 24-year-old baseball player comes into his physician’s office complaining of right shoulder pain that has been going on for several weeks. He has been training intensely during this time period and feels that the pain has gotten worse. The pain is sharp with movement and has started to throb even at rest. On exam, the patient’s vitals are all within normal limits. Both shoulders are symmetrical with no gross deformity, erythema, or muscle atrophy. It is painful for him to actively abduct his right shoulder to 15 degrees, and the pain is worse against resistance. Passive range of motion is full. He has full active range of motion in external rotation, internal rotation, flexion and extension. Strength is 5/5 in all muscle groups. Sensation is intact in all dermatomes and his radial pulses are 2+. He has minimal tenderness to palpation over the bony prominences of the shoulder. The physical exam maneuver depicted in the photograph elicits pain (see Figure A). The muscle that is most likely injured in this patient is innervated by which nerve?