The knee contains two crescent-shaped cartilage constructions called menisci, which work as shock absorbers and facilitate sleek motion in the joint. Tears within the meniscus or cartilage can develop from unexpected twists, deep squats, or degenerative alterations with time.  Surgical reconstruction on the PCL is controversial, and frequently only recommended https://www.theorthopaedicandpainpractice.com/what-happens-if-i-injure-my-posterior-cruciate-ligament/