A 48-year-old female presented to our hospital on referral for evaluation and treatment for pain of the left ankle for approximately 3 months’ duration. She had no history of ankle or leg trauma, and her medical and family histories were unremarkable. The physical examination revealed mild swelling and edema over the lower leg and ankle, more towards the lateral aspect. Tenderness was present over the distal fibula. No neurovascular deficits noted. Ankle range of movement was full, with pain in the terminal range. No evidence of ipsilateral inguinal or popliteal adenopathy. General examination and other system examinations were within the normal limits. The laboratory data, including complete blood count, erythrocyte sedimentation rate, calcium, phosphorus, and alkaline phosphatase levels, were normal. Plain radiographs of her left ankle showed a coarse, perpendicular periosteal reaction with ‘’hair on end’’ pattern and thickening of the shaft of distal fibula (diaphyseal/metaphyseal) cortex, without scalloping or erosion (). The lesion decreased in intensity from the cortical base (medullary surface) toward the surface. The cortex of the fibula was intact, and cortical scalloping was not seen. Computed tomography showed a lesion about one-half of the circumference of the fibula in width without obvious medullary involvement. The foci of mineralization was also seen and which was in continuation with the periosteal reaction (). shows the Magnetic resonance imaging of the patient. The distal end of the fibular shaft for a length of 7 cm showed periosteal elevation on the posterior, lateral, and medial aspects. A 2.1 × 1.7 cm sized focus of lysis within the periosteal reaction was noted on the posteromedial aspect of this periosteal elevation. This focus appears heterogeneously T2 hyperintense, T1 hypointense with mild diffusion restriction. Mild diffuse edema was noted in the surrounding muscles of the posterior aspect of the leg. Minimal edema was noted in the adjacent fibular marrow, but that did not appear significant in proportion to the periosteal changes. Other visualized bones, joints, medial and lateral ligaments, and tendons around the ankle were normal. After initial evaluation and imaging studies, the initial differentials were metastatic disease and primary bone tumor. Ultrasonography (USG) abdomen, USG thyroid, and mammogram were done to rule out a primary in the breast, thyroid, and kidney, and were unremarkable, thus suspicion of a primary bone tumor was made. USG-guided tru-cut biopsy showed () spindle-shaped cells arranged in sheets. The cells had moderate cytoplasm and hyperchromatic nuclei with occasional mitotic figures. Areas of osteoid formation were noted within the spindle cell proliferation. The histological features were consistent with periosteal osteosarcoma. Further, the patient underwent a metastatic workup (NCCT chest and Bone scan), and there was no evidence of metastasis. Hence, the patient was planned for resection with reconstruction. Wide excision (distal fibulectomy) and reconstruction of ankle mortise with ipsilateral proximal fibula done. Tumor was located at the distal fibula, 3 cm above the lateral malleolus. Surrounding muscle fibers were edematous. Wide excision of the tumor with adhered muscle fibers done. Biopsy tract excised en bloc with the specimen. Peroneus longus muscle saved, part of brevis excised. Proximal fibular cut taken 15 cm from the tip of the lateral malleolus (Imaging studies showed periosteal reaction up to 11.5 cm). Ipsilateral proximal fibula exposed and harvested as an autograft. The head of the fibula was reversed and fixed to the lower tibia with two syndesmotic screws and fixed to the remaining shaft of the fibula using a 7 hole titanium plate with screws. shows immediate postoperative radiographs. Excised specimen () showed a tumor mass of 6.5 × 3 × 3 cm over the posteromedial aspect of the distal fibular dia-metaphyseal region accompanied by periosteal elevation. This lesion was located at a distance of 2 cm from the proximal and 7 cm from the distal bony margin. Cut section of the lesion showed gray white and myxoid areas. Histopathological evaluation showed a low-to-intermediate-grade periosteal osteosarcoma. Mitotic rates were 1–2/10 hpf. No areas of necrosis or lymphovascular invasion identified. Closest soft-tissue clearance was 0.5 cm. Both resected margins and skin are free of tumor. Pathologic stage was pT1. The patient had an uneventful postoperative recovery. Initially, the ankle was immobilised in a slab and later changed to below knee cast. Nonweight-bearing continued for 8 weeks, and after that, the patient mobilized on a weight-bearing cast for 4 more weeks. Follow-up radiographs at 6 months and 1 year showed adequate union and congruent ankle mortise. At 6 months and 1 year, the patient was evaluated with USG soft tissue of the left lower leg and NCCT chest, and both were found to be within normal limits and no evidence of local recurrence or metastasis detected. The patient has neither pain related to the surgical site nor difficulty in carrying out her activities of daily living. shows clinical images of the patient’s limb at 1 year follow-up, demonstrating tiptoe standing, standing comfortably, and ankle range of movements with dorsiflexion and plantar flexion. At 1-year follow-up, her Foot and Ankle Disability Index Score is 82.7 and her American Foot and Ankle Score is 77 out of 100.