**Question:** Hypermobility of TMJ is seen in all except

A. Osteoarthritis
B. Dental caries
C. Osteoporosis
D. Ankylosis

**Correct Answer:** D. Ankylosis

**Core Concept:**
The temporomandibular joint (TMJ) is a synovial joint that connects the mandible (lower jaw) to the temporal bone of the skull. Hypermobility of the TMJ is the increased range of motion beyond the normal physiological limits, which can lead to various clinical symptoms and signs. The TMJ is a complex joint with various pathological conditions that can affect its mobility, but some conditions are exceptions.

**Why the Correct Answer is Right:**
Ankylosis is a condition where there is complete fusion of the bones forming the joint, resulting in loss of motion and pain. In this case, the TMJ would be immobile, and hypermobility cannot be present. Thus, Ankylosis is the correct answer as it is an exception to the conditions causing TMJ hypermobility.

**Why Each Wrong Option is Incorrect:**
A. Osteoarthritis: This condition is characterized by joint pain, swelling, and decreased mobility. While there may be some degree of hypermobility in early stages, it is primarily a degenerative joint disorder causing pain and stiffness, not hypermobility.

B. Dental caries: This is a dental condition caused by bacterial infection and destruction of tooth structure. It does not affect the TMJ and is unrelated to hypermobility.

C. Osteoporosis: This is a condition characterized by reduced bone mineral density, which increases the risk of fractures. It does not directly affect the TMJ and is unrelated to hypermobility.

**Clinical Pearl:**
Hypermobility of the TMJ is a clinical concern in certain medical conditions, such as Ehlers-Danlos syndrome, Marfan syndrome, and some joint laxity disorders. Understanding these exceptions to the TMJ hypermobility can help healthcare professionals diagnose and manage patients with TMJ pain and related symptoms appropriately.