One image each of two separate patients with collapse and necrosis of the femoral head, both of which are secondary to repeated injection of steroids. A rapid progression of change in a joint secondary to steroid injections. Transition of a joint from one of minor alterations (such as narrowing, sclerosis) to one of significant bony fragmentation and collapse. Gouged-out areas of bony destruction may be similar to small animal bites, hence the bite sign.
Reference
Martel W, Sitterley BH: Roentgenologic Manifestation of osteonecrosis. AJR Am J Roentgenol 1969, 106;509-522.
