- The temporomandibular joint (TMJ) is classified based on both its structural and functional characteristics.
- Structurally, the TMJ is a synovial joint, meaning it contains a joint cavity filled with synovial fluid, which helps lubricate the movement between articulating surfaces.
- Functionally, it is a diarthrodial joint, which allows for free movement. Specifically, the TMJ permits complex movements such as rotation and gliding, enabling actions like chewing and speaking.

- Unlike fibrous or cartilaginous joints that are either immovable or only slightly movable, the TMJ is highly mobile.
- It also is not a bony fusion or synostosis, where bones are directly fused without a joint cavity. Therefore, the correct classification is synovial, diarthrodial joint.

Key points:
- Structural classification: Synovial joint (presence of a synovial cavity and articular cartilage).
- Functional classification: Diarthrodial joint (freely movable).
- Movement: Allows rotation and translation.
- Contrast with other types: Not fibrous (synarthrotic), cartilaginous (amphiarthrotic), or fused bone (synostosis).

Reference: Gray's Anatomy, 41st Edition, Joint Structure and Function, Chapter 47