A Patient Experiencing Shoulder Pain Is Seen by an Orthopedic

A patient experiencing shoulder pain is seen by an orthopedic specialist who notes erythema, warmth, and fluctuance of the shoulder joint. What is the next step in treatment for this patient?

A) Admit to the hospital for intravenous antibiotics.
B) Inject lidocaine into the joint and reassess in 5 to 10 minutes.
C) Order a plain radiograph of the shoulder to identify possible fracture.
D) Perform a shoulder ultrasound to further evaluate the cause.