You can see on the images that the enthesis when normal has bright collagen turning into almost anechoic unossified fibrocartilage, then smooth bony looking calcified fibrocartilage.
In the abnormal ones you can see the bony irrecularity and the way the ultrasound seems to get into the bone. This is due to the destruction of the enthesis. Once you see this if you look at the adjacent tendon it is going to be abnormal!
Steve