The shoulder joint is made up of three bones. The arm bone, or the humerus, the collarbone, or the clavicle, and the shoulder blade, or the scapula. The bones are connected to each other at two joints. The shoulder joint in itself in the acromioclavicular joint. These joints are surrounded by multiple ligaments around the joints.
The shoulder joint is wrapped around with multiple muscles, essentially important one of those are the rotator cuffs, which insert from the shoulder blades into the ball of the humerus, or the arm bone. There is along here the biceps, which is the arm muscle which comes out of the joint and goes down to the elbow.
The joint stability is provided due to the cup shaped of the joint, as well as a fibrocartilage. It has a rim around it called the labrum. There are multiple nerves and vessels which go around the shoulder and makes it a critical point of the body. The shoulder due to its anatomy has a high range of motion, which also predisposes it to multiple diseases, spatially instability.