My 3 year old was jumping on a trampoline then

Patient: My 3 year old was jumping on a trampoline then started crying saying her leg hurt. Her right knee was warm and a bit swollen. She can bend it without pain but wont walk on it. Weve been putting ice on it and give her motrin. She wont put her leg down to try to put weight on it. What could be the problem?

Doctor: