It is basically a long name for the back of your kneecap hurts. Many people have heard of this even if they don't realize it. It goes by many different names. A few are chondromalacia, patellofemoral disorder, patlellar malalignment, and runner's knee. (Runner's knee is probably the easiet to say!) Patellofemoral pain syndrome is pain behind the kneecap

Patellofemoral means related to the joint between the kneecap and thighbone.

The patellofemoral joint is found in the knee, between the kneecap and thighbone.

The increased q angle typically found in females increases the risk of patellofemoral pain syndrome.

it is not really a joint but protects the HINGE joint at tibia and femur