What is tmj (temporomandibular joint disorder)? what happens inside the joint?

Good question!: Tmj is not one but many conditions known together as temporomandibular disorders. They range from problems with the muscles and the bite to internal derangements of the joint itself. Inside the joint there is a disc which can become displaced, causing painful clicking or popping, locking of the joint, and eventually, a very common kind of arthritis, degenerative joint disease, or osteoarthritis.

Complex: The jaw joint is a very different one from all others. It has a disk which separates the upper jaw bone from the lower jaw bone in all movements of the jaw. It must work in tandem with all the teeth, the other side of the jaw and a myriad of muscles and tendons. Any screwup of any of these parts can cause a tmd.

TMD: TMD (temporomandibular joint disorders) refer to pathological problems within and surrounding the joint. Some derangement of structures. Many types. See an oral surgeon for expert advice.