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Tutorial 106 - Rotational Movements of the Joints
🕑 Added 2016-04-17 06:37:43 +0000 UTC For the limbs, rotation can occur toward the body or away from the body.Medial Rotation
Rotations toward the center of the body are called medial rotation (or internal rotation).
Lateral Rotation
Rotations away from the center of the body are called lateral rotation (or external rotation).
These rotational terms apply to a bone turning on it's own axis. However, there are a few other terms used to describe what's happening with the forearm and the foot. These are supination and pronation.
Pronation and Supination of the Forearm
When the arm is in the anatomical position (palms facing forward), the two bones of the forearm (radius and ulna) are parallel to each other. When the forearm rotates medially the radius pivots at the elbow, crossing over from the outside to the inside. Hence the name radius. The ulna stays fairly in place. You can observe this tactilely by turning your hand while gripping your forearm with the other hand.
Pronation of the forearm is when the hand is facing down.
Supination of the forearm is when the hand is facing up.
Pronation and Supination of the Foot
It's best to think of a runner when talking about these positions. If a runner's weight is bearing on the outside of the foot then we say this is supinated, the foot is turned slightly inwards. The opposite is pronated, weight bearing on the inside of the foot.
We can also use these terms to describe the position of the whole (or any individual part) of the body. For example, laying on the back is the body in supination, on the stomach, pronation.
Again, there are certain muscles responsible for these actions. They're called (no prizes for guessing) pronators and supinators.
Comments
Nathan Aardvark
phew! that's good to know. I always get a bit worried when there's not so many fancy pictures to look at. But I'll try to make some cool looking examples in upcoming tutorials, just to make sure we really cover the joints. :) Thanks for all the likes, Julianne! :)
Julianne McCartney
I've been enjoying all of them! Gives me things to consider about when I'm animating/rigging/skinning. I always like learning anatomy
Nathan Aardvark
Sorry if these ones are a bit ... boring?
