There are muscles called tricep and a bicep, tricep contracts when you extend your arm and your bicep relaxes. When you pull your lower arm up your bicep contracts and your tricep relaxes.
the chicken wing has hinge joints on the elbow like human elbows. In this video, you can see how the tricep contracts when we stretch it and the bicep contracts when we pull the upper arm and lower arm together.—>IMG_0054-2mhnxhk
The chicken wing is very similar to the human arm because they have joints and ball sockets too. There is a ball socket in the shoulder so that humans and chickens can have a full motion in their arm. On the elbow, there are hinge joints that work like a door. It looks like you have a ball socket from the outside of the elbow because it looks like you can move it in a circle but you can move it in a circle because there is a ball socket in the shoulder.