"That Mike Napoli ended up accepting a one-year, $5 million guarantee from the Red Sox after originally agreeing to a three-year, $39 million contract suggested that something pretty bad was going on with his hip. The details came out today, courtesy of Napoli’s agent: Napoli was diagnosed with avascular necrosis in both of his hips.
Avascular necrosis is pretty much what it sounds like: the death of bone due to a lack of blood supply. According to Wikipedia, it’s most common in the hip, though it can also take place at the shoulder, knee and other joints."
......I am not a Dr, but steroid use is a cause of avascular necrosis.
"There are several avascular necrosis causes, some of which are related to trauma (trauma-related avascular necrosis) and some of which are not related to trauma (nontraumatic avascular necrosis). Steroid medicines and alcohol use are the two most common causes of nontraumatic avascular necrosis."