What characterizes disc displacement without reduction?

Disc displacement without reduction is characterized by intermittent locking of the jaw and decreased opening. In this condition, the articular disc associated with the temporomandibular joint (TMJ) has moved out of its normal position but has not returned to its original alignment during jaw movement. This can lead to a feeling of the jaw being "locked" in certain positions, as the disc may block the normal movement of the condyle within the joint.

Decreased opening occurs because the positioning of the displaced disc can restrict the full range of motion of the jaw, leading to limited mouth opening during attempts to open wide. This distinctive feature of intermittent locking alongside reduced mouth opening differentiates this condition from other forms of TMJ dysfunction where full movement might be involved.

Other potential answers present characteristics that are not typically associated with disc displacement without reduction, such as continuous joint noises, which might be more indicative of conditions with disc instability or disc reduction. Excess opening of the jaw generally pertains to hypermobility disorders, while painless jaw movement suggests no underlying mechanical issues, which is not the case with a displacement scenario.