40 patients admitted in Kidwai Memorial Institute Of Oncology , Bengaluru between 2009 to 2016 and  underwent distal femoral or proximal Tibial resection with endoprosthetic  reconstruction  for benign and malignant bone tumors were studied retrospectively.  24 were males and 16 were female patients  belonging to the age group between 16 years and 42 years. After complete staging.  patients underwent surgery for osteosarcoma or aggressive GCT with  modular prosthesis in 22 pateints and custom made prosthesis  used in 18 patients for the Endoprosthetic reconstruction. Patients were followed up for a mean of 18 months and assessed for functional outcome.Complications included superficial and deep seated infections, fractures and local recurrences. Limb sparing surgery after distal femoral and proximal tibial resections  using modular and custom made prosthesis  have similar results  and have shown to be a safe and reliable technique of reconstructing a large bony defect, providing good functional and oncologic outcomes in most patients.. There were no differences noted in the rate of postoperative complications although modular prosthesis is advantageous allowing necessary intraoperative changes and eliminates the waiting period as in the costum made prosthesis which is more cost effective comparatively.