1. If her pain is only in legs around knee without involving any other joints of upper limb, then she might be suffering from osgood schlatters disease or juvenile rheumatoid arthritis
involving only knees +/- rashes
2. But still a complete clinical examination by an orthopaedician is mandatory along with an xray examination of both knees to rule out any other cause,
3. Such pains can occur at this age group, but other causes which might need acute intervention has to be ruled out.
4. Giving a crepe bandage to her knees might help her.
5. Further management depends upon xray finding or if necessary relevant blood investigations depending upon the clinical examination findings.