Toddler developed limp, but X rays show nothing wrong

Hi, my 24 months old son is normally a verly lively and curious little boy. Yesterday, at 5 pm, he started to fall over. I noticed that one of his legs started to give in. He then started to use furniture to lean on, and anything else that would help him to stand up. This is not normally the case. He is very mobile, with good coordination and motor skills.
I took him to A & E, but all blood tests are normal and the X ray was normal too. So, we were sent home. This morning he is worse, and he is refusing to walk all together. When he tries, he lands on his bottom. Now I am really worried, because a/ I don't know what this is;  and b/ because he may injure himself from falling.
He had no injuries or traumas before the accident, so that cannot explain the symptoms. Any advice?

[meniere135]

What kind of x-rays did he have?

[tiredbuthappy]

"About Toxic Synovitis
Toxic synovitis, also known as transient synovitis, is the most common cause of hip pain in children. It is caused by a viral infection that sometimes (but not always) settles in the hip joint. The virus causes swelling at the hip joint, which makes walking painful. Usually just one hip is affected. But later on, the virus can pass to the other hip."

http://kidshealth.org/parent/infections/bacterial_viral/toxic_synovitis.html

If you read the article, you will see that it is not permanent, nor cause for alarm. However, until he receives this diagnosis from an actual doctor, I would keep getting him evaluated and push for answers. But, don't panic, since this is probably what it is.

[AnnieBrooke]

Are his feet and legs warm and normal to the touch?

[elwira127]

Hi Annie, yes- his feet are normal in temperature. He has no temperature, and does not seem in pain. He is frustrated with not being able to get to places, or get his toys, but he didn't seem to be in pain. He knows ward "ouch", and when I asked him, he didn't respond.
Today he is much better, and he can stand on his feelt and wlka (with a little limp, and a bit stiff, but walking!). I decided not to go back to hospital, because the whole expereince was very traumatic. Aha, and I gave him some ibuprofen for the last two days, so that might have helped.