Reciprocal Click or Anterior Disc Displacement with Reduction

Once again, thank you to the original (unknown) author of this video. 

 

1) Jaw Resting Position

Compare the resting position of the condylar head, it is sitting backwards and upwards. The ligaments and capsule that cross the joint line have shortened and are creating compression on the disc. The discs response to compression is to displace forward creating a barrier for movement. Overcoming this barrier under compression leads to a clicking sound, and more importantly from a diagnostic point of view, you can clearly see a second reciprocal click on closing as the condyle drops backwards off the disc. The first click is the jaw reducing back into the correct place, the closing click is moving out of place.

2) Compartmentalised Movement

The distinctive roles of the inferior and superior compartments have been lost, the jaw over rotates and compresses the posterior joint capsule before finally overcoming the obstruction.  

3) Retrodiscal Tissue

When the disc is displaced forward, the retrodiscal tissue can sit across the joint surface and be compressed on basic jaw movements like chewing. This is a common source of pain referring into the ear and pain after function, remembering that the inner workings of the jaw joint are aneural and don’t have the capacity to report pain. 

4) Alveolar Bone Density

As mention in the normal video, the alveolar bone has become compromised and lost its density and white colour. 

5) Disc Position

Once the condyle reduces back onto the disc, you can see that even in this severely affected jaw, the condyle can still translate quite a long way forward though in this case, it would be painful as it is weight bearing on the retrodiscal tissue. This is why it is important to assess a clicking jaw that is changing its properties, as these secondary degenerative changes will be occurring without the patient necessarily feeling them.

 

Author: Nigel Smith