Purpose: Anatomic configuration of the ankle joint is useful information during various ankle procedures. This study was prospectively designed to investigate the sagittal inclination pattern of the ankle joint. Materials and Methods: Lateral standing ankle radiographs from one-hundred people (age: $17{sim}68$, M:F=45:55) and magnetic resonance (MR) sagittal ankle images from twenty-four people (age: $16{sim}65$, M:F=14:10) were studied. Post-traumatic, arthritic, or grossly deformed ankles at any reason were excluded. The posterior inclination angle (PIA) of the distal tibia was measured and compared between the lateral and the medial segment. Results: On plain radiographic data, the average PIA of the distal tibia was $6.14^{circ}{pm}3.56^{circ}$ (range $0^{circ}$ to $14^{circ}$) in the lateral segment and $13.16^{circ}{pm}3.05^{circ}$ (range $6^{circ}$ to $22^{circ}$) in the medial segment. On MR imaging data, the average PIA of the distal tibia was $5.08^{circ}{pm}4.26^{circ}$ (range $1^{circ}$ to $10^{circ})$ in the lateral segment and $10.16^{circ}{pm}4.87^{circ}$(range $5^{circ}$ to $17^{circ}$) in the medial segment. The PIA between two segments was significantly different. Conclusion: The sagittal configuration of the medial area ankle joint and the lateral area ankle joint has difference in the degree of posterior inclination and shape of curvature.