In which of the following conditions does internal derangement cause mandibular deviation to the same side?
**Core Concept**
The question tests the understanding of **temporomandibular joint (TMJ) pathology**, specifically the effects of internal derangement on mandibular movement. Internal derangement refers to an abnormality in the relationship between the **articular disc** and the **condyle** of the mandible.
**Why the Correct Answer is Right**
In cases of internal derangement, the disc can become displaced, leading to pain and limited movement of the jaw. When the disc is displaced to the same side as the affected joint, it can cause the mandible to deviate towards the affected side upon opening due to the altered mechanics of the joint.
**Why Each Wrong Option is Incorrect**
**Option A:** This choice is incorrect because it does not accurately describe the typical presentation of internal derangement.
**Option B:** This option is also incorrect as it contradicts the known pathophysiology of TMJ internal derangement.
**Option C:** Similarly, this choice does not align with the expected clinical findings in internal derangement of the TMJ.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that the direction of mandibular deviation can help in diagnosing the side of the internal derangement. Understanding the relationship between the disc, condyle, and mandibular movement is crucial for diagnosing TMJ disorders.
**Correct Answer:** D. Unilateral internal derangement with the disc displaced to the same side as the affected joint.