Arthroscopy: arthroscopy, a minimally invasive procedure could be performed in which a small camera is inserted in to the knee joint to visualise the buildings inside of. The obvious way to diagnose a PCL tear is to look at the knee for posterior sag at ninety levels of knee flexion https://www.theorthopaedicandpainpractice.com/what-happens-if-i-injure-my-posterior-cruciate-ligament/