Diagnosis of Chondroblastoma
During a physical exam, the doctor obtains a complete medical history of your child, and conducts neurologic function tests for:

reflexes
muscle strength
eye and mouth movement
coordination
alertness
 
Other diagnostic tests may include:
x-rays: produce images of internal tissues, bones, and organs onto film

MRI (magnetic resonance imaging): produces detailed images of organs and structures within the body; especially useful for assessing soft tissue around injured joints and bones

computed tomography scan (CT, CAT scan): uses a combination of x-rays and computer technology to produce 3-D cross-sectional images (slices), both horizontally and vertically, of the affected area-including bones, fat, soft tissue

bone scan: detects bone diseases and tumors; can determine the cause of bone pain or inflammation

biopsy or tissue sample from the tumor: provides definitive information about the type of tumor; this is collected during surgery