Experts are uncertain about the exact cause of temporomandibular joint (TMJ) disorder but believe that it may be caused by a variety of factors. In many cases, the cause is due to several interwoven reasons. Some of the most common possible causes include:

• Clenching the jaw
  
  
• Dental procedures (e.g., orthodontics to change the bite)
  
  
• Genetics
  
  
• Hormones
  
  
• Low-level infections
  
  
• Autoimmune diseases
  
  
• Bruxism (teeth grinding or clenching)
  
  
• Stress
  
  
• Trauma, such as facial injuries sustained in a sports or car accident
  
  
• Arthritis in the jaw

• Scar tissue that develops after radiation therapy to the head or neck
  
  
• Other musculoskeletal problems (e.g., degenerative joint disease, internal joint derangements)
  
  
• Stress of muscles around the jaw (e.g., poor posture while looking at TV or computer monitor)