Severe Knee pain for 2 months. Consult!

Our 12 years old daughter has been suffering from Knee pain.. On Dec 8th she hit iron bench at school.. No pain found for 5 days.. She got little pain 12th.. Used pain killers for 2days.. Consulted Doctor on 15th.. Gave some antibiotics and pain relief but no use.. Suggested to take blood, Xray, MRI ESR 101 Some fluid formed at knee patella.. Prescribed injection Zostem 1.5gm (Cefoperazone (1000mg), Sulbactam (500mg) 10days and other Little relief in pain Changed to Tablets Ceftum 500mg for 10days Taxim 200 for 20days Infection came down but not pain Again introduced Taxim 200 and Lizolid 600mg 2 weeks But no relief in pain Then done arthroscope to see whether any chondral erosion.. But no use.. Knee absolutely clear.. No damage and no infection found.. Doctors who got gold medal in ortho to consult Rheumatologist.. Now we are in confusion and remained at 1st step and no other step found to go.. Please suggest anyone.. What to do and whom to consult