William Soriano, DC | Apex Chiropractic

The alar ligaments are paired stabilizing ligaments of the craniocervical junction, the place where the neck and head meet. These ligaments extend primarily from the lateral aspects of the odontoid process of the axis(C2), toward the medial surfaces of the occipital condyles(C0).

Their principal mechanical role is to restrain/check excessive axial rotation, lateral bending, and, to a lesser degree, flexion-extension motion of the head and upper cervical spine. They function bilaterally as part of an integrated stabilizing system rather than standalone stabilizers.

Alar ligament injury may happen when craniocervical trauma induces severe rotational, lateral-bending, distraction, or high-energy forces. However, diagnosing an isolated alar ligament injury/tear is difficult. Symptoms can be nonspecific and physical examination cannot independently establish the injury/tear. Plus, conventional MRI findings may be variable or difficult to interpret, especially if the right slice, stack, or sequences are not properly ordered/taken.

An alar ligament injury cannot be determined by any one single method. Instead, take into account and integrate:

Mechanism of injury
Neurological findings
Craniocervical alignment
Osseous imaging
Ligament-sensitive MRI when indicated
Dynamic imaging in selected cases
Specialist consultation when instability is suspected

An abnormal signal within an alar ligament does not automatically mean a traumatic rupture or clinically meaningful instability is present.

Figure 1. Overview of the craniocervical junction demonstrating the occiput, atlas (C1), axis (C2), odontoid process, and major stabilizing ligaments.

The alar ligaments are two short, strong bands of dense connective tissue located at the craniocervical junction. Alar derives from the Latin word for “wing.” When viewed from the front, the right and left ligaments extend outward and upward from the odontoid region in a wing-like fashion.

They form part of the ligamentous complex connecting:

The occiput
The atlas
The axis
The odontoid process

Their main purpose is to regulate and limit excessive motion between the skull and the upper cervical spine. The alar ligaments are located deep within the craniocervical junction.

Located:

Lateral to the apical ligament of the dens
Anterior to portions of the tectorial membrane
Superior and lateral to the transverse ligament
Between the dens and the medial occipital condylar region

Figure 2. The paired alar ligaments extend from the lateral aspects of the dens to the medial occipital condyles.

The ligaments are typically not visible on standard X-rays or CBCT because these modalities primarily depict mineralized tissue. MRI is the principal imaging used when direct evaluation of ligament integrity is indicated. Each alar ligament typically originates from the upper lateral surface of the odontoid process.

The exact attachment may vary in:

Height
Width
Fiber orientation
Shape
Relationship to adjacent connective tissues

The dens attachment is generally narrower than the occipital attachment.The fibers then travel superiorly and laterally to attach primarily to the medial surfaces of the occipital condyles.This orientation allows the ligaments to span the transition between the axis and skull while crossing both the atlantoaxial(C1/C2) and atlanto-occipital(C0/C1) regions.

Figure 3. Atlas and axis demonstrating the osseous relationships supporting the alar ligaments.

Some anatomical descriptions may include fibers extending toward the lateral mass or other components of the atlas, but the presence of a distinct atlantal portion has not been consistently established.This variability is important because simplified anatomical diagrams may imply that every person has identical, sharply defined alar ligament bundles. Actual anatomy is more complex, especially in this area.

The alar ligament fibers and shape are described as:

Cord-like
Fan-shaped
Ovoid
Rounded
V-shaped when viewed together

Fiber orientation varies among individuals. Fibers may travel:

Nearly horizontally
Superolaterally
Slightly inferolaterally
In mixed bundles with different orientations

Figures 4/5. Posterior view illustrating the relationship between the occipital condyles, atlas, axis, and alar ligaments and odontoid process demonstrating the attachment site of the alar ligaments.

Orientation influences when each ligament becomes tensioned during movement. A more horizontal ligament may respond differently to rotation than a ligament with a stronger superior or inferior orientation. Therefore, anatomical variation may influence both normal motion and how ligaments appear on MRI.

The alar ligaments are composed primarily of collagen-rich dense connective tissue organized to resist tensile loading forces. In a cadaveric tensile study involving 19 ligament specimens, failure occurred between 87 and 346 newtons, with a mean failure force of approximately 187 newtons. However, the specimens came from older adult cadavers, meaning these values should not be treated as universal thresholds for living patients of all ages. Also, laboratory failure does not represent the exact force necessary to produce injury during a real world collision. Biological injury largely depends on:

Direction of force
Speed of loading
Head position
Repetition
Combined rotation and translation
Bone quality
Age
Existing degeneration
Congenital anatomy
Contributions from surrounding ligaments

The alar ligaments are particularly important in restraining excessive upper cervical axial rotation. During rotation of the head, the ligament opposite the direction of rotation will become more tensioned.

For example:

Right head rotation tensions the left alar ligament.
Left head rotation tensions the right alar ligament.

This description is useful, but it should not be interpreted as an absolute on-off mechanism. Both ligaments interact with the transverse ligament, facet joints, joint capsules, tectorial membrane, muscles, and osseous geometry. Cadaveric studies have demonstrated increased motion at both C0-C1 and C1-C2 following alar ligament transection. More recent robotic testing found that unilateral alar ligament sectioning increased lateral bending, axial rotation, and flexion-extension motion.

The same study estimated that the intact alar ligaments contributed approximately 19% of resistance to axial rotation and 16% of resistance to lateral bending under the tested conditions.These figures describe one experimental model and should not be interpreted as fixed percentages in every living patient.

Lateral Bending

The alar ligaments also limit excessive lateral bending. Lateral bending produces coupled motion within the craniocervical junction. Because the ligaments cross from the dens to the occiput, side bending changes their length and tension.The opposite-side ligament is generally expected to become more tensioned, although fiber orientation and coupled rotation may alter the precise loading pattern.

Flexion and Extension

The alar ligaments are not the primary restraints to sagittal-plane motion, but experimental evidence shows that they contribute to stability in both flexion and extension.Their influence should therefore be understood as multidirectional rather than limited exclusively to rotation.The ligaments work as a paired system.

Mechanical modeling suggests that injury to one ligament may alter how the entire bilateral restraint mechanism functions. The remaining ligament does not necessarily act as a complete substitute for the injured side.

Relationship to Other Craniocervical Stabilizers

Figure 6. The major stabilizing ligaments of the craniocervical junction.

The alar ligaments should never be evaluated in isolation. Craniocervical stability depends on the combined function of:

Transverse ligament of the atlas
Cruciform ligament
Tectorial membrane
Atlanto-occipital joint capsules
Atlantoaxial joint capsules
Apical ligament
Anterior and posterior membranes
Osseous congruity
Suboccipital musculature
Neuromuscular control

The transverse ligament is especially important in restraining anterior translation of the atlas relative to the dens.The alar ligaments primarily regulate rotational and lateral motion, but they also assist in preventing excessive displacement when the broader stabilizing system is stressed.

A patient may therefore have:

An isolated alar abnormality
A combined alar and capsular injury
Multiligamentous injury
Osseous injury with secondary ligament compromise
MRI signal changes without mechanical instability

These are not equivalent clinical situations.

Injury Mechanisms

Alar ligament injury is most plausible when the head and upper cervical spine are exposed to substantial:

Axial rotation
Lateral bending
Distraction
Flexion-extension
Combined multiplanar loading

Potential mechanisms include:

Motor-vehicle collision
High-energy whiplash
Contact-sport collision
Diving injury
Fall from height
Direct cranial impact
Craniocervical distraction
Severe rotational trauma

Minor neck pain alone is insufficient evidence of alar ligament injury, however, the probability of meaningful ligament disruption increases when the mechanism is accompanied by:

Fracture
Dislocation
Abnormal craniocervical alignment
Neurological deficits
Severe occipital pain
Marked guarding
Altered consciousness
Other indicators of high-energy trauma

Possible Clinical Presentation

There is no symptom pattern that is specific enough to diagnose an alar ligament injury without further evaluation. The following presentations may raise suspicion of alar ligament involvement.

Potential findings may include:

Upper cervical or suboccipital pain
Pain aggravated by rotation
Restricted or guarded head movement
Sensation of instability
Headache
Dizziness
Visual-motion sensitivity
Nausea
Disequilibrium
Neurological complaints after trauma

These symptoms overlap with many other disorders, including:

Cervical muscle injury
Facet-joint injury
Concussion
Vestibular disorders
Migraine
Occipital neuralgia
Vertebral artery pathology
Upper cervical fracture
Atlantoaxial instability
Craniocervical dissociation

Symptoms alone cannot determine ligament integrity.

Physical Examination

Alar Ligament Stress Tests

Clinical tests described for evaluating possible alar ligament compromise include:

Rotation stress test
Side-bending stress test
Lateral shear-type testing
C2 spinous-process or “kick” test
Bending-rotation test

The theoretical basis is that controlled movement of the skull should produce early tension through the alar ligament and associated motion of C2.

Interpretation Limitations

Manual examination has important limitations.

A positive test may reflect:

Pain
Muscle guarding
Normal anatomical variation
Capsular restriction
Examiner technique
Generalized hypermobility
Apprehension

Cadaveric biomechanical testing demonstrated measurable motion changes after alar ligament transection, but the investigators specifically noted that it remains uncertain whether clinicians can reliably feel changes of that magnitude. A small diagnostic study reported moderate accuracy for several manual alar ligament tests when compared with MRI, but the sample was limited and MRI itself is not a perfect gold standard for functional instability. Clinical testing should therefore be regarded as part of a screening process, not definitive proof of injury.

Safety Principle

Provocative upper cervical stress testing should not be performed aggressively when the patient has:

Recent high-energy trauma
Suspected fracture
Suspected dislocation
Severe neurological symptoms
Signs of craniocervical instability
Possible vascular emergency
Marked midline tenderness
Inability to actively control the head

In these situations, stabilization and appropriate medical imaging take priority.

Imaging Radiographs

Routine radiographs cannot directly visualize the alar ligaments, but they may demonstrate indirect evidence of instability, including:

Abnormal alignment
Lateral-mass asymmetry
Increased atlantodental interval
Fracture
Translation
Abnormal motion on appropriately indicated dynamic studies

Apparent asymmetry on open-mouth imaging may also result from head rotation, positioning, beam geometry, or normal anatomy.

CT and CBCT

CT and CBCT provide excellent visualization of:

Occipital condyles
Atlas
Axis
Odontoid process
Joint alignment
Fractures
Congenital variants
Degenerative change

However, a structurally intact-looking bone study does not directly establish normal alar ligament tissue. CT is generally favored in acute trauma because it is fast and highly effective for identifying fracture and gross osseous malalignment. CBCT can provide detailed osseous anatomy at relatively high spatial resolution, but it is not a substitute for MRI when direct ligament or neural-tissue evaluation is required.

MRI

MRI may visualize the alar ligaments using high-resolution, thin-section sequences oriented to the craniocervical junction.

Potential MRI observations include:

Fiber continuity
Ligament thickness
Signal intensity
Asymmetry
Surrounding edema
Associated tectorial or transverse-ligament injury
Hemorrhage
Joint effusion
Neural or soft-tissue injury

MRI interpretation is technically difficult because the ligaments are small, obliquely oriented, and anatomically variable.

Figure 7. Normal coronal MRI of the craniocervical junction.

MRI Signal Changes and Whiplash

Earlier studies reported increased high-signal changes in the alar ligaments of some patients with chronic whiplash symptoms. These observations led to proposals that MRI could identify persistent ligament injury. Subsequent research raised substantial concerns about this interpretation.

High-signal changes have also been identified in:

Uninjured individuals
Patients with nontraumatic neck pain
People without demonstrable instability

Prospective research found that upper cervical ligament high-signal changes after lower-grade whiplash were not predictive of outcome at 12 months. Follow-up imaging also found that these signals did not meaningfully change over the first year and were similarly prevalent in whiplash patients and noninjured patients with chronic neck pain. The investigators concluded that some of these appearances were more likely normal variants than traumatic lesions. Therefore, high signal within an alar ligament is not, by itself, proof of traumatic rupture, instability, or the cause of a patient’s symptoms.

Reliability of MRI Diagnosis

Even in major craniocervical trauma, MRI assessment of the alar ligaments can show inconsistent agreement between observers. One study evaluating MRI for ligament injury in atlanto-occipital dissociation found unsatisfactory interobserver and intraobserver reliability for alar ligament assessment. The authors emphasized the need for standardized imaging and interpretation protocols.This does not mean MRI is useless, it means MRI findings must be interpreted alongside:

Trauma mechanism
CT findings
Neurological status
Alignment measurements
Other ligament findings
Dynamic stability when appropriate
Clinical progression

Isolated Alar Ligament Injury

Isolated alar ligament injury appears to be uncommon and is reported primarily through small case series and case reports.The available literature does not establish one universally accepted treatment protocol. Management has included:

Temporary rigid immobilization
Activity restriction
Clinical observation
Repeat imaging
Dynamic CT or radiography
Specialist consultation
Gradual return to activity after stability is established

A 2024 case review emphasized that the significance of treating an MRI finding alone remains uncertain and that clinical recovery and demonstration of stability are important components of decision-making.

Differential Diagnosis

When alar ligament injury is considered, the differential diagnosis should include:

Osseous Injury

Occipital-condyle fracture
Atlas fracture
Odontoid fracture
Axis fracture
Atlanto-occipital dislocation
Atlantoaxial dislocation

Ligamentous Injury

Transverse-ligament injury
Tectorial-membrane injury
Capsular injury
Multiligamentous craniocervical injury

Neurological and Vascular Conditions

Spinal cord injury
Brainstem injury
Vertebral artery dissection
Concussion
Traumatic brain injury
Cervical nerve injury

Musculoskeletal Conditions

Suboccipital strain
Facet-joint injury
Cervicogenic headache
Occipital neuralgia
Myofascial pain
Temporomandibular dysfunction

Vestibular Conditions

BPPV
Peripheral vestibular injury
Vestibular migraine
Persistent postural-perceptual dizziness

Red Flags Requiring Urgent Medical Evaluation

Urgent assessment is warranted after trauma when the patient presents with:

New limb weakness
New numbness or loss of coordination
Difficulty walking
Loss of bladder or bowel control
Altered consciousness
Severe or rapidly worsening occipital pain
Cranial-nerve abnormalities
Difficulty swallowing or speaking
Double vision
Drop attacks
New facial sensory changes
Inability to support or control the head
Signs of fracture or dislocation
Symptoms concerning for vascular injury

These findings should not be attributed to a routine upper cervical “misalignment” without appropriate emergency evaluation.

Upper Cervical Chiropractic Considerations

The alar ligaments are directly relevant to upper cervical practice because they regulate motion between the skull, atlas, and axis. However, their clinical significance must be presented accurately.

What Can Be Stated Confidently

The alar ligaments contribute to upper cervical rotational and lateral stability.
Trauma can injure the alar ligaments.
Loss of ligament integrity may increase craniocervical motion.
CBCT cannot directly establish ligament integrity.
MRI findings require clinical correlation.
Suspected instability changes the risk profile of manual treatment.

What Should Not Be Claimed Without Evidence

That atlas displacement automatically means alar ligament injury
That a rotated atlas on static imaging proves ligament laxity
That MRI signal automatically represents traumatic tearing
That dizziness confirms alar ligament pathology
That manual palpation can definitively diagnose a tear
That an upper cervical adjustment repairs a structurally torn ligament
That every patient with whiplash requires specialized alar ligament MRI

Treatment-Safety Principle

When significant ligamentous instability is suspected, forceful end-range rotation, aggressive stress testing, and high-velocity procedures should be avoided until instability has been appropriately investigated.

Upper cervical care should be considered safe and appropriate after:

Fracture has been excluded
Major instability has been excluded
Neurological status is understood
Imaging has been reviewed where clinically indicated
The selected procedure is compatible with the patient’s structural condition

Dizziness and Neurological Symptoms

The upper cervical spine contributes sensory input to systems involved in head-position awareness, balance, eye-head coordination, and postural control. An injury affecting the upper cervical joints, muscles, or ligaments could plausibly alter afferent input from the region. However, a direct chain such as alar ligament abnormality to brainstem dysfunction to then dizziness cannot be assumed in an individual patient without supporting evidence.

Dizziness after trauma may instead arise from:

Concussion
BPPV
Vestibular injury
Migraine
Medication effects
Autonomic dysfunction
Cervical sensorimotor disturbance
Psychological and perceptual factors
Multiple simultaneous causes

The alar ligaments are therefore clinically relevant to upper cervical stability but should not be used as a universal explanation for post-traumatic neurological symptoms.

Patient Explanation

The alar ligaments are two small but important stabilizing ligaments near the top of the neck. They connect the second cervical vertebra to the base of the skull and help prevent the head from rotating or bending too far. A major accident can potentially stretch or tear these ligaments, but the symptoms are not unique. Neck pain, headache, dizziness, and stiffness can result from many different injuries.

The ligaments are also difficult to evaluate. They cannot be seen directly on standard X-rays or CBCT, and even MRI findings may not always distinguish injury from normal anatomical variation. For this reason, diagnosis should be based on the entire clinical picture rather than one symptom, one physical test, or one imaging observation.

FAQ

Can an alar ligament heal?

A partial ligament injury may heal or scar over time, but healing depends on the severity of injury, blood supply, mechanical stability, age, health status, and whether the region is repeatedly stressed. Complete disruption associated with instability requires specialist management.

Can CBCT show an alar ligament tear?

No. CBCT may show fractures, alignment, joint relationships, and congenital anatomy, but it does not directly demonstrate the soft-tissue fibers of the alar ligaments.

Is MRI definitive?

No. MRI is the most useful modality for direct ligament assessment, but image quality, sequence selection, anatomy, reader experience, and normal variation affect interpretation.

Can a patient have abnormal MRI signal without instability?

Yes. High-signal changes have been reported in people without acute injury and do not necessarily represent traumatic rupture or mechanical instability.

Can the ligaments cause dizziness?

Upper cervical injury may contribute to altered sensorimotor input, but dizziness has many possible causes. An alar ligament abnormality should not be assumed to be the cause without a broader neurological, vestibular, vascular, and cervical evaluation.

Can an adjustment repair a torn ligament?

A manual procedure does not biologically reconnect a completely torn ligament. Management depends on the severity of injury and stability of the craniocervical junction.

Should the alar ligaments be tested after every whiplash injury?

Not necessarily. Testing should be guided by injury mechanism, symptoms, examination findings, neurological status, and clinical suspicion. Aggressive testing may be inappropriate in acute or high-risk trauma.

References

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