Extreme pain when kneecap is physically moved

My dog backed up into my knee about a month ago and caused severe pain in my knee. Luckily it didnt swell very much. I am able to walk fine and bend it like normal bit when it gets physically moved while my leg is straight, it still causes extreme pain. My 6 mo old grand daughter was on my legs and moved just right and I almost went thru the ceiling! What could be going on under the kneecap? 😏