The anterior suprapatellar fat pad is an intracapsular, but extrasynovial structure, located just posterior to the quadriceps tendon, anterior to the prepatellar joint recess, and superior to the patellar base and retropatellar cartilage, usually triangular in shape. 

Anterior suprapatellar fat pad signal abnormalities and mass effect (indicating edema), with no other significant findings, and the clinical presentation in this case, are compatible with anterior suprapatellar fat pad impingement syndrome.