About
The ulna is situated on the inside of the joint and forms a cup shape which allows articulation with the humerus. The radius is the smaller of the two forearm bones and sits on the outside of the joint. The radial head is round and again cup-shaped to allow it to move around the wide base known as the capitulum of the humerus.
There are actually three joints at the elbow. The first being the hinge joint formed between the humerus and the ulna called the humeroulnar joint, which allows us to bend and straighten our elbows.
The second is the humeroradial joint between the radius and humerus which again allows flexion and extension but is also involved in the more complex motion of turning the hand over so the palm faces up or down. This movement of the forearm is called supination (palm up) and pronation (palm down). The third is a pivot joint formed by the radius and ulna and is called the proximal radioulna joint.
There are actually three joints at the elbow. The first being the hinge joint formed between the humerus and the ulna called the humeroulnar joint, which allows us to bend and straighten our elbows.
The second is the humeroradial joint between the radius and humerus which again allows flexion and extension but is also involved in the more complex motion of turning the hand over so the palm faces up or down. This movement of the forearm is called supination (palm up) and pronation (palm down). The third is a pivot joint formed by the radius and ulna and is called the proximal radioulna joint.
