Superior PTFJ dislocation

Ive had problems with the lower outside of my knee for years, with growing instability. Recently, while lying in bed, I moved to shift and had a large pop on the side of my knee resulting in significant pain, and my knee locking all together. I could feel the bony protrusion with my hand. Further, my roommate had to manually reduce my leg. I am confident it was a superior PTFJ dislocation but my PCP said it’s not possible without a “substantially more traumatic mechanism of injury”. I have had traumatic injuries to the side of my knee before but was too young to effectively understand and seek treatment for them.

On the topic,
Should I seek alternate care?
How should I prevent this from happening again?
Beyond RICE and gradual stretching/strengthening what would you recommend as far as self treatment?