Student Pulls Heel Hook in School Bathroom Fight

Two students square off in a school bathroom. The BJJ practitioner pulls guard immediately, dragging the fight to the filthy tile floor covered in who knows what. His opponent lands on top throwing punches but the grappler ignores the strikes. He's hunting for something specific. His hands grab the standing leg, controlling the ankle and knee.

The heel hook entry develops fast. The BJJ kid wraps the leg, isolates the foot, and begins rotating. His opponent stands over him throwing weak punches downward but realizes something's wrong with his knee. The rotation increases. The foot twists further than it should. Pain registers on his face as the pressure builds on ligaments not designed to handle this torque.

The standing fighter has every opportunity to stomp or kick the face of the person twisting his leg apart. He doesn't. Instead he taps frantically on the grappler's shoulder. Multiple taps, desperate taps. The BJJ practitioner releases immediately, respecting the submission signal despite this being a bathroom brawl with no referee.

Both kids stand up covered in bathroom floor filth. Did the heel hook cause permanent knee damage despite the tap? Was the angle wrong enough to save the ligaments or did something tear anyway?