What is the pulled elbow?
It is one of the disorders with the highest frequency in the external injuries of the elbow in a child.
It often occurs at two to six years old children, and recurrence is repeated, and it stops occurring with aging without realizing.

When a child has a hand pulled suddenly or it falls over by turning an arm down, the arm will not rise suddenly.
A child will cry out.

Let’s think about the cause.
Let’s look at the bone of the left arm 　

Left humerus side

 　
thumb side
Ulna radius 　
Left hand side 　

There is an annular ligament (the one in pink) on the head of radius.
This ligament is fixing the radius so that a radius may not fall out to the lower one.
Looking at the left elbow from the front. Looking at the left elbow from the outside

1 is the head of a radius

2 is neck
Annular ligament is twisting around the surround of a neck.

A child’s radius
A radius is growing, and since a head of radius are in a state like a stick, it will fall out from the annular ligament by slight external force.
When we grow up, a head of radius becomes large and constriction is formed so that it will not fall out from the annular ligament.

Yellow shows a ligament in the left animation.

:If you pull on the arm suddenly

A head of a radius arises sneaking through an annular ligament.

It is the feature that a pulled elbow does not accept a swelling unlike fracture.

Let’s consult an orthopedics.