The most mobile bones of the body attach to one another in a series of "ball and socket" joints, around which they can pivot and rotate. These joints are often deep inside the body, and not visible to the naked eye. For example, consider the thigh connecting to the hip.
A small protrusion of bone known as the "Femoral head" joins the femur to the hip socket. This socket is so ensconsed in muscle and fatty tissue that it can't be easily seen. And yet for most, once it's mentioned, it's easy to picture where that connection must be. Stand up. Walk around. Stand on one foot and lift and twist your free leg. It's easy to see that your leg is joined to your hip at a single connection point, from which all the positions your leg can take originate. This is true of all the mobile bones in your body. The range of motion allowed by each one's individual socket might differ, but the concept remains the same. When you've completed the line of action and the three ovals representing the head, rib cage and pelvis, try to quickly note down the major pivot points of the body. These are:
- Hip socket
Now connect the dots, and you've recorded the basic underlying anatomy required for a useful gesture study. From here, you can begin to work up the musculature of the body.
Mastering the basics of the skeletal underpinnings of the body will make all of your drawing faster, easier, and more convincing, whether from life or from your imagination. It is a crucial part of beginning to master perspective. Even if you intend to work in a "cartoony" style, knowing the rules will allow you to break them in effective, planned ways, rather than leaving you at the mercy of accident.
To learn more about joints, check out: