Dentists do not treat TMJ!!

Why do my docs keep telling me to talk to my dentist about my TMJ? I've had a bite guard for 25 years. It protects my teeth but it doesn't stop me from clenching all night and waking up with the resulting headache at 4am. What do other docs think a dentist can do? Feels like they're both just shoving it off on the other practitioner. Last thing my wise dentist said was try PT 🤷‍♀️