Background: This paper aims to compare the inherent geometry of the human lumbar spine in supine, standing, and sitting postures. Carried out at the Department of Anatomy and Radiology, Qazi Hussain Ahmad Medical Complex (QHAMC), Nowshera the study's objectives are to offer a detailed understanding of the morphological adaptation and mechanics of the lumbar spine during different postures. Objectives: The present study is a descriptive cross-sectional study at the Anatomy with the collaboration of the Radiology Department of QHAMC Nowshera. One hundred patients aged 20 to 70 years were involved in the study. Study design: This cross-sectional, descriptive study Duration and place of study: Department of Anatomy and Radiology faculty at Nowshera Medical College (NMC), Nowshera from DEC 2023to May 2024 Results The study involved 100 patients, with a mean age of 25 years and a standard deviation of 15 years. It was identified that there are differences in the lateral curvature and axial inclination of the lumbar region according to the supine, standing, and sitting positions. Standing posture showed that the lumbar spine had higher lordosis than the supine one (p<0.05). The sitting posture revealed that the sitting forward curve was significantly (p . < 0.05) less than the supine and standing postures, and the sitting back curve was significantly (p < 0.05) more than the two other postures. Conclusion Regarding the intrinsic curvature of the lumbar spine, it was found that its shape changes depending on the patient's position, whether supine, standing, or sitting. Knowledge of these changes is vital for diagnosing spinal disorders, reconstructing treatment, designing ergonomic solutions, and creating effective rehabilitation programs. More studies should be conducted to understand the effects of the mentioned postural changes on spinal biomechanics and related health consequences.