Whats the difference between tmj & lock jaw?

TMJ vs Lockjaw: Lockjaw refers to a medical problem where the jaw muscles will not allow jaws to open due to a tetanus infection. However, there are several other causes of a jaw not opening involving the masseter muscle which are related to spasm or trismus. Tmj is the joint of the jaw and there are a number of conditions related to it that block the opening of the jaw too, i.e. Disc displacement.

Symptom: Symptoms of tmj/tmd can vary from person to person, severity, location and duration. It can affect the ears: ringing, aching, roaring, stuffiness, hearing loss; head, facial and neck: headaches, neck and facial pain; locking of the jaw: closed lock- limited opening, open lock- can't close; bite problems: can't touch the teeth, grinding, clenching; toothaches; lose teeth, fatigue, etc.

Different: LockJaw (Trismus), a pathological condition in which the mouth is held shut by sustained spasm of the masseter (jaw) muscle, often observed in cases of tetanus. Tetanus, an infectious disease of the central nervous system. TMJ is a disorder of the jaw joint and associated structures