Well I guess this didn’t allow to enlarge the image as much as I’d hoped, but the key finding is the super femoral head - ie a crescenteric subchondral lucency = the so-called “crescent sign” of avascular necrosis (specifically stage 3).

References:

Crescent sign: http://radiology.rsna.org/content/217/1/213.full

Ficat stages (I quickly made this chart using the reference below)

Adapted from: http://radiopaedia.org/articles/avascular-necrosis-of-the-hip-classification