A child with a history of pain over lower extremities since few moths shows radiological evidence of osteosarcoma. Most common site of osteosarcoma is:

The classic form of osteosarcoma is typically seen in patients in their second or third decade, with a peak in the adolescent growth spu. It occurs more frequently in males than in females and is found in the metaphyseal areas of long bones, with 50% of lesions seen about the knee joint. The distal femur is the most common site, followed by the proximal tibia and then the proximal humerus. Ref: Randall R.L., Hoang B.H. (2006). Chapter 6. Musculoskeletal Oncology. In H.B. Skinner (Ed), CURRENT Diagnosis & Treatment in Ohopedics, 4e.