A 17-year-old male basketball player presents with right lateral thigh pain for the past 3 weeks. He had a collision with another player 5 weeks ago that resulted in a bruise that has since resolved. He is mildly tender over the lateral mid-thigh in the soft tissues and has a decreased knee flexion. You obtain X-rays (Figure 1). What is your suspected diagnosis? What is your initial workup in the ED? What imaging confirms the diagnosis? What is your management and disposition?