Jointing Joints

Does anybody know how the knee and elbow joints on a standard bjd are cast? Are they done separately from the shin and forearm and then attatched after casting? It's the most logical way I can think of for them to be properly hollow, but I was hoping someone with a bit more experience could confirm that for me. Are any of the other sections done like that or just the knees and elbows (I already know the wrists and ankles for sure are). Is the neck generally like that too? I know there's a few different ways dolls seem to have their necks... Can anybody tell me what they think is the best kind of neck-joint? If possible send a picture of it? I would really appreciate it.