Suddenly stopped Walking

My 2 year old son suddenly stopped walking. He was walking normally in the morning and had his breakfast then we he tried to stand up and walk he felt pain in his knee and below and had to crawl.
He has no fever and there is no swelling or bruise on his leg. he can bend his knee normally.
We are very worried. please tell us what to do.

[mamaz073]

Take him to the paediatrician  or emergency room  ...it might be something serious.

[Hossein_Karami]

Hi, Thanks for your feedback.
After he finished his breakfast as usual started walking to his room playing with his toys, but suddendly sat down and pointed in his knee area, he again tried to stand up but failed with a lot of pain so that he had to crawl. He had no fever or no lump or any unusual thing on his knee and when I called his doctor he asked me to give him Brufen to ease the pain. the medicine was effective and in the evening he was again able to walk but not as usual. He had no surgery or any deseases related to his bones but last month he caught cold with running nose and it took him almost three weeks to get better.

After one day he started walking again as if there was no pain again.
We took him to a pediatric and he watched my son walking and also did some other physical examination on his both legs. Everything seemed to be normal. So his doctor suggested no more investigation like sonar is needed and asked us not to be worry.

I would like to know if we should persue the matter further.
He is no fine. He walks, runs and play as usual again but we are still a bit worry.
Your feedback is highly appreciated.