Final answer:
The hip reaches maximum extension during the terminal stance phase of the gait cycle, where the hip joint's multiaxial ball-and-socket structure provides stability and motion essential for walking.
Step-by-step explanation:
In normal gait, the hip joint reaches its maximum extension during the terminal stance phase of the gait cycle. This is the phase when the heel of the weight-bearing leg initially makes contact with the ground, progressing to when the same foot is lifted off the ground. During this phase, the hip of the supporting leg extends to help propel the body forward. The extension of the hip joint at this point is crucial for providing the necessary leverage and momentum for the swing phase of the opposite leg.
The hip joint is a multiaxial ball-and-socket joint that provides both stability and a wide range of motion, necessary for such complex actions as walking. Stability during standing and walking is maintained through tightly pulled supporting ligaments that secure the head of the femur within the acetabulum. This type of joint is critical to bear the body's weight during the gait cycle.