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Topic

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Lateral atlantoaxial joint

The lateral atlantoaxial joint is a paired synovial articulation between the inferior articular facets of the atlas (C1) and the superior articular facets of the axis (C2). These plane-type synovial joints allow rotation of the head and neck, contributing to approximately 50% of cervical rotation. Each joint is enclosed by a fibrous capsule reinforced by the capsular ligaments, and contains synovial fluid to facilitate smooth movement.

The lateral atlantoaxial joints are oriented obliquely in the axial plane, permitting rotational motion while maintaining stability through ligamentous support, including the transverse ligament of the atlas, alar ligaments, and the joint capsules. Degenerative changes, trauma, or inflammatory processes can compromise joint integrity, leading to atlantoaxial instability, pain, or restricted movement.

Function

  • Enables rotation of the head and neck

  • Maintains atlantoaxial stability through capsular and ligamentous support

  • Facilitates smooth gliding motion between C1 and C2

  • Contributes to load transfer from skull to cervical spine

  • Serves as a landmark in spinal imaging and surgical planning

Synonyms

  • Lateral C1-C2 joint

  • Lateral atlantoaxial articulation

  • Facet joint of atlas and axis

MRI Appearance

T1-weighted images:

  • Joint space is low signal intensity, surrounded by hypointense cortical bone of C1 and C2 facets

  • Articular cartilage appears slightly intermediate signal

  • Surrounding fatty marrow in the vertebral bodies is high signal, enhancing contrast

  • Pathology such as joint effusion, degenerative changes, or trauma may alter signal intensity

T2-weighted images:

  • Articular cartilage and joint space appear hyperintense if fluid is present, while cortical bone remains hypointense

  • Degenerative changes such as cartilage loss or joint effusion are readily visualized

  • Useful for assessing inflammation, synovitis, or ligamentous edema

STIR (Short Tau Inversion Recovery):

  • Normal joint capsule and bone remain low signal

  • Edema, synovitis, or inflammatory changes appear hyperintense, highlighting acute injury or arthritis

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal joint capsule shows minimal enhancement

  • Pathological conditions (inflammation, infection, or post-traumatic changes) demonstrate capsular or synovial enhancement, aiding diagnosis

CT Appearance:

  • Cortical margins of C1 and C2 facets are hyperdense, clearly outlining the joint

  • Joint space may be visualized as a small gap between the articular surfaces

  • Excellent for assessing fractures, osteophytes, degenerative changes, and congenital anomalies

  • Axial and coronal reconstructions provide optimal visualization of atlantoaxial alignment and rotational anatomy

MRI images

Lateral atlantoaxial joint MRI sagittal image

MRI image

lateral atlantoaxial joint MRI coronal image