TMJ disorders can occur if:

The disk erodes or moves out of its proper alignment.
The joint's cartilage is damaged by arthritis.
The joint is damaged by a blow or other impact.
The muscles that stabilize the joint become fatigued from overwork, which can happen if you habitually clench or grind your teeth.
Accidents – trauma to the head or neck caused by falls, sports injuries, car accidents, etc.
Bad habits such as clenching or grinding of the teeth, poor posture, improper sleep habits

• Forward Head posture (i.e. when you jut your head forward when working on a computer for hours; or cradling the phone between your shoulder and ear; or reading a book)

Misalignment of the upper and lower jaw
Problems with the bite. When the Upper and Lower teeth do not fit properly.

• Poorly fitting dentures
• Missing or misaligned teeth