Some people mistake this for a shoulder dislocation, and vice versa. This is a very different injury than a shoulder dislocation. Let's look at what structures are involved in this injury. The part of the scapula that makes up the roof of the shoulder is called the acromion. There are ligaments that hold these two bones together.
Ligaments are soft tissue structures that connect bone to bone.
One set of ligaments surround the joint and make up the joint capsule. Two other ligaments hold the clavicle down, and attach the clavicle to a bony knob on the scapula called the coracoid process. The AC joint can be injured in varying degrees . As the shoulder strikes the ground, the force from the fall pushes the scapula down. The collarbone, because it is attached to the rib cage, cannot move down enough to follow the motion of the scapula.