Which muscle assists in flexing the coxal joint?

The psoas major is a key muscle involved in flexing the coxal joint (hip joint) due to its anatomical positioning and functionality. It originates from the lumbar vertebrae and inserts into the lesser trochanter of the femur. When the psoas major contracts, it pulls the femur towards the trunk, resulting in flexion at the hip joint.

This muscle plays a significant role not only in hip flexion but also in stabilizing the lumbar spine, making it crucial in movements that require bending at the hips. It is seen as a primary mover in actions like walking, running, and sitting down, where the flexion of the hip is necessary.

While other muscles mentioned may play various roles in hip and lower body movements, they do not primarily assist in flexing the coxal joint in the way that the psoas major does.