In Figure 1, decreased signal intensity is observed in the femoral head (wedge shape), which strongly suggests AVN. MRI is the most sensitive test for detecting AVN. Plain radiographs can be negative in early AVN. There is no evidence of hip fracture on this patients MRI, and she had no history of recent trauma. Osteoarthritis has a more insidious course and would not progress this rapidly (this patients hip pain developed over 5 days). Trochanteric bursitis causes lateral hip pain; Patricks maneuver would not be positive in trochanteric bursitis.