The hips! We shake them when we dance, glare at them when we diet, and use them every day with barely a thought. They support the weight of the body in both static (e.g. standing) and dynamic (e.g. walking or running) postures. These joints are the most important part in retaining balance and crucial elements in any figure drawing.
In art, the hips are essential in order to display a realistic pose. Take, for example, the Contrapposto. This is when a person stands with most of their weight on one foot. The hips naturally slant in one direction, giving the figure a sense of weight, balance, and grace. The shoulders instantly slope in the opposite direction from the hips, giving the human form a slight sense of sway. To see an example of contrapposto, you need only look around a room of standing people. Artists have been utilizing this pose since the 4th century BC. Of course, one of the most famous examples is the sculpture of “David” by Michelangelo.