Conversation so far:
where does the head of the humerus fit into the scapula
The head of the humerus fits into a shallow socket on the scapula called the glenoid.
in what part of the body is the glenoid
The glenoid cavity or glenoid fossa of scapula is a part of the shoulder.
is there any cartilage in the glenoid cavity
The glenoid cavity surface is covered with cartilage in the fresh state, and its margins, slightly raised, give attachment to a fibrocartilaginous structure, the glenoid labrum, which deepens the cavity.

Question: how can the structure be torn
Self-contained rewrite: how can the glenoid labrum be torn