TMJ and TMD - Jaw Click & Jaw Lock Explained for TMJ Disorder | Dr. Agatha Bis

In Temporo-mandibular Joint Disorder, also known as TMD, a common sign is a click or a pop in the jaw joint, often called TMJ, which stands for Temporo-Mandibular Joint.

In a healthy joint, we have the head of the jaw joint, called the condyle, seated centered in the glenoid fossa of the skull, with the articular disc in between acting as protection and insulation for the condyle against forces and wear.

In a healthy TMJ, when a person opens and closes, the condyle slides down the eminence, and the articular disc slides with it in order to support and protect the condyle at all times. This is a healthy relationship between the condyle, the articular disc, and the glenoid fossa, and the movement of opening and closing is silent.

When a person feels or hears a click, that usually indicates that the condyle is seated posterior to where it should be, and the disc is located in front of it when the teeth are touching. As a person opens, the condyle moves down the eminence and “clicks” back onto the disc, which then allows a silent further opening of the jaw. When the condyle clicks back onto the disc, typically people don’t have pain associated with this but may experience pain or tension when the condyle clicks off. The condyle clicks off the disc as the person goes to close again and if the teeth are not touching where the condyle and disc should be positioned, then the muscles will force the jaw to close further until the teeth touch, resulting in a posterior positioning of the condyle, which causes it to “click” or “pop” off the disc, leaving the disc in front of it displaced. This is called “Disc Displacement with Reduction”.
When a person has a click for some time but doesn’t do anything about it, in some cases, the constant clicking off and on the disc will result in damage to the condyle or tearing of the posterior connective tissue and the condyle will be seated more posteriorly or the disc will remain anterior to the condyle due to this damage or tearing. This will cause the condyle to be unable to “click” back onto the disc and, depending on where the disc is now positioned, the person may experience jaw lock, or inability to open wide. The disc, being anteriorly displaced, prevents the condyle from popping back onto it and this causes the condyle to be stuck and unable to move further down the eminence. People with locked jaw may have pain associated with it, and have difficulty chewing if the connective tissue has been damaged or the condyle has degenerative changes as a result of this chronic dysfunction.

00:00 Introduction
00:10 Healthy Joint
00:44 Disc Displacement causing Jaw Click
01:07 Disc Displacement causing Jaw Lock

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