The arm slammed into his throat and Batman fell onto his back. It felt for a moment that his windpipe had been crushed and it took him a few seconds to catch his breath. By the time he did, the Joker was on top of him. He struggled underneath the madman. One arm still free, he struck upwards, aiming for the Joker's ribcage. Against the floor, he didn't have much room to pull back his fist and gain momentum, so it was a weaker swing than he would've liked. He had to get up. This was not an advantageous position.