What is the main muscle involved in hip joint extension?

The gluteus maximus is the primary muscle responsible for hip joint extension. This muscle is the largest and one of the most powerful in the body, originating from the posterior aspect of the ilium and sacrum and inserting on the femur. Its primary function is to extend the hip joint, which is critical during activities such as standing up from a seated position, climbing stairs, and running.

In terms of the other muscles listed, while the gluteus medius plays a significant role in hip abduction and stabilization, it is not the primary mover for hip extension. The psoas and iliacus are primarily hip flexors, meaning they work to bring the thigh toward the torso rather than extending the leg backward. This differentiation in muscle function highlights why the gluteus maximus is the correct choice for hip joint extension.