Question

We can move our arms in circular motion but not our elbow why

Answer 1

arms are made up of ball and socket type joint but elbow is made up of hing joint which is only move in one direction

other example of hing joint:- phalanges, knee and elbow

Answer 2

EXPLANATION:

We can move our arms in circular motion but not our elbow because the joints at the elbow are the ball and the socket joint whereas the joints that are present in our elbow is the hinge joint. The ball and the socket joints can be rotated to 360 degree.  

The ball and socket consists of a rod fixed in a cup and therefore it moves in all directions whereas the hinge joint moves only in a fixed plane.