Let’s Break It Down Part 1- Demystifying a TMJ Diagnosis

“TMJ” as I have discussed before can encompass a lot of different things. I am going to hit some of the highlights of the most common things I see in my practice that can fall under the diagnostic heading of “TMJ Disorder.”

1. Disorders of the joint itself
2. Disorders of the muscles in the head/neck
3. Neuropathic Pain

First things first- Disorders of the Joint Itself. There are a variety of things that can fall in this category. The most common disorder of the joint is an internal derangement or dislocation of the articular disc. In between the jaw bone (called the condyle) and the skull lies a cartilage disc or cushion that allows you to open and close your mouth without these two bones bumping into each other. Due to acute accidental trauma (a fall, a hit, an airbag deploying, a whiplash injury) or from repetitive microtraumas (such as clenching/grinding), that little cushion can slip forward. When that happens, you start to notice your jaw starts to click or pop when you open and close. The sound is caused by the cartilage disc sliding in between the two bones. The “popping” is the disc actually sliding back into it’s normal position so that you are able to fully open your mouth.

Eventually the disc can slide so far out of position that the popping may stop. When that happens, patient’s often start to think their TMJ has resolved, when it actually is a signal that the damage is progressing/getting worse. Patients who stop popping usually have a disc that is no longer going into the proper position and they can no longer open as wide as they once did. It is oftentimes at this point that the inflammation progresses to the point that pain in the actual joint starts. This type of pain usually presents as a constant sharp or dull pain that happens directly in front of the ear canal. It can sometimes present as ear pain or ringing in the ears as well. Over time, if this condition remains untreated, the two bones begin rubbing together when you open, close, swallow, speak or chew food and the bone will start to deteriorate, which begins to cause the arthritic breakdown of the joint space. This breakdown, when severe, can lead to a patient needing a full joint replacement! Did you know surgeons can do total joint replacements of the jaw just like a knee or hip replacement?

So how do you know if the disorder is in the joint itself? The only way to know FOR SURE is to have an MRI which tells us where the disc is on opening and closing. That, however, can be a very expensive and time consuming way to figure it out, and I often don’t recommend imaging unless treatment is not going how I would expect or if the diagnosis isn’t clear based on the clinical presentation. I usually can make the diagnosis based on clinical findings and a detailed history. When I see a patient with an articular disc disorder or internal derangement here are the signs and symptoms:

• History of popping and clicking that is ongoing or has ceased
• Limited opening when no pop/click is present (opening to 1 or 2 finger widths stacked as opposed to 3 fingers width which is normal)
• Deviation (or movement of the jaw to the side) when opening
• Change in the bite position that has happened gradually over time (a patient hitting more on one side usually indicates arthritis in the side where the bite is heavy)
• Ear pain on the affected side
• Difficulty moving the jaw to the opposite side of the affected joint
• Pain on closing the teeth together
• Pain on palpation of the space directly in front of the ear

A thorough exam by a trained professional will help make or confirm a diagnosis of internal derangement. Stay tuned, next post will be on muscle disorders of the head and neck!