Tear and detachment of the prepatellar continuation beautifully seen in this case of complete tear of quadriceps tendon (figs attached).
Anatomy of this region nicelly published by my brazilian friends Rodrigo Aguiar, Daniel Pastore and Don Resnick:
https://www.ajronline.org/doi/10.2214/AJR.07.3107
https://www.ajronline.org/doi/full/10.2214/AJR.05.1466
Best,
Atul