You can find different definitions hiding under these concepts, so, as with the hip rim or hips, it is worth to clarify this.
The shoulder (often used interchangeably with the term shoulder joint) is a term referring to the part of the upper limb rim (shoulder rim), which consists of the shoulder joint, the shoulder-collarbone, the collarbone-sternum joint and the joint between the scapula and the chest wall, not being a joint in the anatomical sense (but this joint functions as a joint), but is held in its proper position primarily by the muscles.
The shoulder hoop consists of two shoulders connected by a bridge.
Below are engravings showing this area: first a general front view of the chest with the shoulder girdle, then a front and rear view of the shoulder, as well as a close-up of the shoulder and shoulder-collarbone.
It can be seen that the connection of the shoulder girdle is not as tight as in the case of the hip girdle, which is related to the function of this part – the upper part of our body is used to perform precise, fluid movements, while the pelvis gives us a “base”. Thanks to this, we have greater mobility in this part of the body (the largest range of movements among all joints), but it is also prone to overload and damage.
If we look again at the shoulder joint, we see that it has a small and shallow pelvis and therefore the stabilization of the head of the humerus in the pelvis depends mainly on the interaction of muscle forces, in contrast to other joints in which stabilization is largely determined by passive elements. It should be remembered that this joint takes part in almost every movement of the upper limb, this is because it is a multi-axis joint, in which movements take place around an infinite number of axes.
In addition to the muscles, which, as you can see, are not missing, do not forget about the fascia-a tissue that greatly affects the lack of mobility or mobility of this area (about fascia I will write later).