Site : Metaphysis of the lower end of the femur, the upper end of the tibia and humors.
Age incidence
-         10-25 years (prior to epiphyseal fusion)
-         Old age (Secondary to paget’s disease)
Sex- Boys > Girls
The tumour extends within the medulla and across the physeal plate and extending into the soft tissue. Grey white invasive and destructive masses having focal haemorrhase & nerosis. There are areas of bone loss and cavitation alternate with dense patches of abnormal new bone.

Clinical Features
Ø Pain, swelling, near a joint with history of trauma
Ø Overlying skin stretched & shiny
Ø Local rise of temp due to increased vascularily
Ø Firm in consistency
Ø Sign & symptoms of bronchitis, pnenmonia if there is lung metastasis
Ø Pathological fracture
Spread- haematogenous spread to lung, usually sometimes to other bone.
Types:
a)    Primary or Secondary
b)   Dahlin’s prognostic classification
Ø Osteoblastic
Ø Chondroblastic
Ø Fibroblastic
c)    Geschickter and copeland classification
Ø Selerosing type
Ø Osteolytic type
Ø Both osteoblastic and osteolytic (Mixed)
Ø Telangicetatic.
X-ray
1.    Both osteolytic (Radiolucent) & osteolbastic (Dense) areas
2.    Sunray appearance – due to deposition of tumour osteoid along the vessels.
3.    Codman’s triangle- due to raised periosteum

CT & MRI: To see extend of the tumour
X-ray Chest: To see pulmonary metastasis.

Biopsy
1. FNAC
2. Open biopsy

Varients of osteosarcoma
Parosteal                :    A thin gap between cortex & tumour, cortex is not corded.
Periosteal               :    A superficial defect of the cortex
Paget’s sarcoma    :    Feature’s of paget’s disease + Bone destruction with soft tissue invasion.
Treatment
·       Multi-agent chemotherapy for 8-12 weeks
·       Resection of the tumour or amputation
·       The pathological specimen is examined to assess the response to preoperative chemotherapy. It tumour necrosis is marked, chemotherapy is continued for another 6-12 months.
·       Bone gap is filled by a large bone graft and custom-made implant.