This chapter explores the biomechanics of the human skeletal system, focusing on the distribution of gravitational forces on the skeleton and pelvic ring. It examines how these forces vary with posture, movement, and specific activities, highlighting the role of the pelvis in force transmission between the trunk and lower limbs. The pelvic ring’s structure, composed of bones, joints, ligaments, and muscles, is crucial for maintaining stability and mobility during everyday activities. The chapter also delves into the pathologies affecting the pelvic region, such as fractures and sacroiliac joint dysfunctions, and their clinical implications. Further, it discusses bone metastases, detailing their histological features and the impact of osteolytic, osteoblastic, and mixed metastases on bone integrity. The importance of understanding bone biomechanics in the treatment of bone metastases is emphasized, particularly with regard to the use of cementoplasty and combined screw fixation. The chapter highlights the need for a multidisciplinary approach in managing pathological fractures, improving patient outcomes, and ensuring long-term stability and pain relief.