system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is a posterior wall fracture?

Tua Tagovailoa sustained a dislocated hip and posterior wall fracture. I need a medical professional's explanation as to what exactly occurred to satisfy my pea brain.
gpt
It's probably referring to the posterior wall of the acetabulum, which is the medical term for the hip socket (comes from the Latin for "vinegar cup"). 

The hip is a ball and socket joint. The top end of the femur (thigh bone) has a ball on it which fits into the acetabulum (socket). In a dislocation, the thigh is pulled away from the pelvis so strongly that the ball comes out of the socket and can't get back in. At the same time the posterior surface - the back surface - of the socket has cracked. Sore.