Final answer:
Resistance to pelvis on femur flexion is provided by gluteal muscles and hip joint ligaments. The femoral neck's strength is crucial in supporting body weight and facilitating leg movements. Knee joint articulations, especially the tibiofemoral joints, contribute to femoral rotations necessary for flexion and extension.
Step-by-step explanation:
The phrase 'pelvis on femur flexion' refers to the movement at the hip joint where the angle between the pelvis and the femur decreases. This movement is in the sagittal plane and involves an anterior bending, such as lifting the thigh towards the torso. The resistance to this movement is primarily provided by the hip extensor muscles, which include the gluteal muscles such as gluteus maximus, gluteus medius, and gluteus minimus, and also by the hamstrings which cross the hip joint posteriorly. Additional resistance comes from the ligaments of the hip joint itself, such as the iliofemoral, pubofemoral, and ischiofemoral ligaments, which get tightened during extension and serve to pull the head of the femur tightly into the acetabulum, providing stability.
The mechanics of the femur and how it supports body weight are also crucial in understanding movement and resistance. The neck of the femur transfers the downward force of the body weight horizontally to the vertical shaft of the femur. This structure must be strong enough to resist the forces applied during movements like flexion and extension at the hip joint.
Moreover, the articulations at the knee joint play a role in the movement of the leg. Specifically, the medial and lateral tibiofemoral joints allow for the femur to perform slight rotations which are important during flexion and extension of the knee. Muscles such as the popliteus are important in initiating the unlocking of the knee from full extension to allow for flexion to occur.