i am glad to help you out. your nephew needs urgent and through evaluation from an orthopedician. one possibility for his symptoms can be osgood schlatter disease in which there is tender swollen bump just under their knee cap on the tibial tuberosity. although usually just on one knee both knees can also be affected. this bump can appear as enlarged knee cap. it can cause pain during certain activities such as running kneeling jumping etc. he needs to get an x-ray and mri knees done. moreover other causes also need to be ruled out. treatment includes nonsteroidal anti-inflammatory drugs such as ibuprofen rest putting ice on the area knee braces and knee immobilizer. i sincerely hope that helps. take care.
"my nephew about 3 years old has an enlarged left knee cap. his left knee bone (cap) is bigger than the right and he can't stretch his legs straight. sometimes he complains pain and does not want to walk on his own. he crawls when he feels the pain. as far as we know he didn't have any injury. please advise.