Pathologic conditions mimicking osteonecrosis.

MRI has become increasingly helpful in establishing an early diagnosis of avascular necrosis(AVN). AVN often demonstrates a classic pattern on MRI; findings earlier in the course of the disease are less specific. Many pitfalls can complicate interpretation, and a number of pathologic conditions can share features of early AVN on MRI and plain radiographs. These entities should be distinguished from AVN, because treatment and prognosis may differ significantly.