Anatomy chapters
Joints of the head and neck (TMJ)
The temporomandibular joint in detail (its disc, ligaments, movements and dislocation), plus the atlanto-occipital and atlanto-axial joints of the upper neck.
- The TMJ is a synovial joint between the mandibular condyle and the mandibular fossa and articular eminence of the temporal bone.
- An articular disc splits it into upper (gliding) and lower (hinge) compartments.
- The neck's key joints: atlanto-occipital (yes) and atlanto-axial (no).
On this page
Overview
The temporomandibular joint (TMJ) connects the mandible to the skull. It is used in chewing, speaking and yawning.
It is a synovial joint with an articular disc. It works as a hinge and a gliding joint together.
The other key joints of this region are between the skull and the top two vertebrae: the atlanto-occipital and atlanto-axial joints.
Temporomandibular joint
Articular surfaces
- Above: the mandibular fossa and the articular eminence (tubercle) of the temporal bone.
- Below: the head (condyle) of the mandible.
The joint surfaces are covered by fibrocartilage, not hyaline cartilage, because the bones form by membrane ossification.
The articular disc
An oval plate of fibrocartilage lies between the bones. It divides the joint into two separate synovial cavities:
- Upper compartment: between the disc and the temporal bone. Gliding (forward and back) happens here.
- Lower compartment: between the disc and the condyle. Hinge (rotation) happens here.
The disc is attached around its edge to the capsule. In front, the lateral pterygoid tendon attaches to it.
Capsule and ligaments
| Ligament | Attachments | Notes |
|---|---|---|
| Lateral (temporomandibular) | Articular tubercle to the neck of the mandible | Strengthens the capsule; stops backward displacement |
| Sphenomandibular | Spine of sphenoid to the lingula of the mandible | Accessory; remnant of the first arch (Meckel's) cartilage |
| Stylomandibular | Styloid process to the angle of the mandible | Accessory; part of the deep cervical fascia |
Nerve and blood supply
- Nerves: the auriculotemporal and masseteric branches of the mandibular nerve.
- Arteries: branches of the superficial temporal and maxillary arteries.
Movements of the TMJ
| Movement | Muscles |
|---|---|
| Depression (opening) | Lateral pterygoid, helped by digastric, geniohyoid, mylohyoid; gravity |
| Elevation (closing) | Temporalis, masseter, medial pterygoid |
| Protrusion | Lateral and medial pterygoids together |
| Retraction | Posterior fibres of temporalis |
| Side to side (grinding) | Pterygoids of one side acting with those of the other side alternately |
When the mouth opens wide, two things happen together:
- The condyle rotates on the disc (lower compartment).
- The condyle and disc glide forward onto the articular eminence (upper compartment).
When the mouth is fully open, the condyle sits below the articular eminence. This is the position from which it can dislocate.
Clinical relevance
Dislocation of the TMJ
How it happens: yawning very widely, a blow to the open jaw, or a long dental procedure. The condyle slips forward in front of the articular eminence.
What you see: the mouth is stuck open and the patient cannot close it. Spasm of the masseter, temporalis and medial pterygoid holds it there.
Reduction: press the molars downward (with the thumbs well protected) and then backward, so the condyle passes back over the eminence.
TMJ dislocation is almost always anterior.
Temporomandibular disorder
How it happens: problems with the disc or muscles, teeth grinding or stress.
What you see: pain in front of the ear, clicking and limited opening. Pain can spread to the ear because both share the auriculotemporal nerve.
Fracture of the neck of the mandible
How it happens: a blow to the chin.
What you see: the condyle is pulled forward and medially by the lateral pterygoid.
Atlanto-occipital joints
These are paired synovial (condyloid) joints between the occipital condyles and the superior facets of the atlas (C1).
They allow nodding (flexion and extension), as in saying "yes", and a little side bending.
Atlanto-axial joints
There are three synovial joints between the atlas (C1) and axis (C2):
- Median atlanto-axial joint: a pivot joint between the dens of the axis and a ring formed by the anterior arch of the atlas and the transverse ligament.
- Two lateral atlanto-axial joints: plane joints between the facets.
They allow rotation of the head, as in saying "no".
Ligaments
- Transverse ligament of the atlas: holds the dens against the anterior arch. With upper and lower bands, it forms the cruciate (cruciform) ligament.
- Alar ligaments: from the dens to the sides of the foramen magnum; they limit rotation.
- Tectorial membrane: the upward continuation of the posterior longitudinal ligament to the occipital bone.
If the transverse ligament ruptures (trauma or rheumatoid arthritis), the dens can press on the spinal cord and medulla, which can be fatal.
Atlanto-occipital says "yes"; atlanto-axial says "no".
Common angles: the type of cartilage on the TMJ, what happens in each compartment, the muscle attached to the disc, the direction of dislocation and how it is reduced, the nerve supply, and the movements at the atlanto-occipital and atlanto-axial joints.
Quick revision
- TMJ: synovial, condyle with mandibular fossa and articular eminence.
- Fibrocartilage surfaces; disc divides upper (gliding) and lower (hinge) compartments.
- Lateral ligament is the main ligament; sphenomandibular is a Meckel's cartilage remnant.
- Lateral pterygoid opens the mouth and pulls the disc forward.
- Dislocation is anterior; reduce by pushing down then back.
- Atlanto-occipital: yes. Atlanto-axial: no. Transverse ligament holds the dens.
Written by The House Job from standard anatomy references (Snell's Clinical Anatomy by Regions is the book named in the UHS PGET syllabus).
FAQ
What type of joint is the TMJ?
A synovial joint with an articular disc, working as a hinge in its lower compartment and a gliding joint in its upper compartment.
Which nerve supplies the TMJ?
The auriculotemporal and masseteric branches of the mandibular nerve.
In which direction does the mandible dislocate?
Forward, in front of the articular eminence.
What movement occurs at the atlanto-axial joint?
Rotation of the head, as in shaking the head to say no.