A 28-year-old woman presents with a 6-month history of progressive swelling and pain in the left knee. Plain radiographs show an eccentric, lytic lesion in the distal femur extending to the articular surface with a soap-bubble appearance. MRI confirms a lesion measuring 4 cm × 3 cm with heterogeneous signal intensity. A biopsy confirms giant cell tumor of bone. The lesion is intra-articular and extends to the subchondral bone. What is the most appropriate next step in management?