Chondroblastoma (also known as Codman Tumor) is a rare benign neoplasm of cartilaginous origin, it occurs mostly in males less than 20 years, and occurs most commonly in the epiphysis of long bones.  

Plain radiographs and CT will show a smooth or lobulated lucent lesion, thin sclerotic rim, possible endosteal scalloping, solid periosteal reaction, and internal chondroid calcification in 50% of cases.

On MRI it shows cartilage signal intensity (intermediate on T1 weighted images, high signal on T2 and STIR weighted images) and shows heterogeneous moderate post-contrast enhancement

Differentiating between a chondroblastoma and clear cell chondrosarcoma can be difficult with MRI characteristics and patient age helping to differentiate.