2 year Kid unable to walk Properly. Now?

Hi Doctor, My kid is 2 year male, On December 16 - he was running very fast in evening- at night he started saying some pain in right leg. Later we had seen mild swelling in ankle on next morning. Mild fever also there. Withinn 48 hours we had visited doctor. With x ray report doctor said it's normal bleeding from muscle. Within 3 day ferver completely reduced and only he was not able to walk properly in right leg. Later we waited more than 27 days but it's not recovered still.. He is unable to walk properly.. Jan 11- after 20 days fever started and currently he is having fever since last 3 days.. Checked with pediatric doctor and he took all the blood test and suspected remothoid arthritis. So he took RF test and ASO.. Reports attached it shows normal.. Still he is unable to walk properly is there any chance for remothoid arthritis for my 2 years baby? What I have to do now?