Visible Popping Over Fibular Head

Hi guys,

As the title suggests, my left knee/fibular head pops every time I try to squat/flex my knee with an anterior pelvic tilt. Its not immediately painful on its own, but after 25-30 pops in a row it starts to ache. See below for a gif of the aforementioned snap, taken sitting on the floor with an extended lower back, dragging my heel towards my torso. If I release my lower back and do the same motion the popping disappears. My physiotherapist has given me some hip/knee stretches/stabilizers to perform, but I wanted to know if anyone else might have a differing opinion/idea about what's going on. Thanks in advance!

Visible Knee/Fibular Popping - Album on Imgur