8yo competitive irish dancer with left knee pain for two days with slight limp on occasion. x-ray normal. dr thinks overuse of knee. should i get evaluated further ask for blood work or mri?

Some basics: To have any 3rd party (insurance) pay for an MRI you would have to meet their criteria which include exam findings & duration of problem. I doubt seriously they would approve it based on your post. Blood work is also unnecessary unless physical findings suggest the need. If you are willing to pay out of pocket for all rather than give it a rest/wait, you can likely find someone willing to do it.

Competitive Athlete: Best option is to rest. Competitive athletics/dance in young child common reason for this kind of problem. No reason for further evaluation. Child's emotional health also best protected by taking a break. If this is a year round endeavor as in other competitive dance, don't get swept away by the endeavor, other parents, coaches. Knee over toe mechanics probable contributor.