When the other man pushed, David shifted his right leg farther out and used the leverage he had on the trapped leg to prevent the roll, then dropped onto his back and brought his right leg back in to hook around Dylan's right wrist, pulling it out from under him to remove any leverage he might have gained from it, then began applying force to the trapped leg in order to hyper-extend or even break the knee. A LOT of force, in fact, using his hip as the fulcrum point of this makeshift lever to prevent the leg (which would now be between his own legs) from simply hitting the floor and going no further.