Chiropractic Safety: Known Risks and Contraindications

Chiropractic care carries a documented safety profile that spans minor transient discomfort to rare but serious adverse events, including vertebral artery dissection and cauda equina syndrome. This resource catalogs the known risk categories, absolute and relative contraindications, and the regulatory and clinical frameworks that govern disclosure and risk stratification in chiropractic practice across the United States. Understanding these parameters is essential for patients, referring clinicians, and policymakers evaluating the role of spinal manipulation in musculoskeletal care. The reference material draws on published positions from the World Health Organization, the American Chiropractic Association, and documented clinical literature indexed by the National Institutes of Health.

• Definition and Scope
• Core Mechanics or Structure
• Causal Relationships or Drivers
• Classification Boundaries
• Tradeoffs and Tensions
• Common Misconceptions
• Checklist or Steps (Non-Advisory)
• Reference Table or Matrix

Definition and Scope

The safety profile of chiropractic care is formally bounded by two overlapping categories: adverse events and contraindications. An adverse event, in clinical nomenclature, is any unintended outcome causally or temporally linked to a therapeutic intervention. A contraindication is a clinical condition in which a given treatment is inadvisable because the risk of harm exceeds any plausible benefit.

The World Health Organization's WHO Guidelines on Basic Training and Safety in Chiropractic (2005) categorizes chiropractic adverse events as either minor/benign or serious, and establishes that spinal manipulative therapy (SMT) carries contraindications that must be assessed before treatment. The document identifies two primary contraindication classes — absolute and relative — which have since been adopted, in modified form, by licensing bodies across all 50 U.S. states as part of the clinical competency frameworks administered through the National Board of Chiropractic Examiners (NBCE).

Scope in this context is national. Every state licenses chiropractors independently, but all states require passage of NBCE Part IV (Practical Examination), which includes direct assessment of the candidate's ability to identify contraindications before performing adjustive procedures. This means safety screening is a licensure-level requirement, not a professional courtesy, across all U.S. jurisdictions. For a broader review of the regulatory structure, the page on chiropractic regulation and oversight covers the state-board framework in detail.

Core Mechanics or Structure

Chiropractic spinal manipulation applies a high-velocity, low-amplitude (HVLA) thrust to a specific vertebral segment, or a lower-force mobilization technique, with the goal of restoring segmental motion and reducing pain-related neuromuscular dysfunction. The biomechanical forces involved vary substantially by technique — the diversified technique employs manual HVLA thrusts, while the activator method uses a spring-loaded instrument generating forces measured in the range of 0.5 to 4.0 kg, depending on the device setting.

The tissues most directly loaded during cervical HVLA manipulation include the joint capsule of the zygapophyseal (facet) joints, the intervertebral disc annulus, the anterior and posterior longitudinal ligaments, and critically, the vertebral artery as it traverses the transverse foramina of C1–C6. Mechanical strain on the vertebral artery during end-range rotation and extension is the primary proposed mechanism for the most serious adverse event associated with cervical manipulation: vertebrobasilar stroke secondary to vertebral artery dissection (VAD).

For lumbar manipulation, the primary structural risk involves the intervertebral disc and the neural elements of the cauda equina. A pre-existing large central disc herniation at L4–L5 or L5–S1, when subjected to an HVLA posterior-to-anterior or rotational thrust, can theoretically be displaced further, compressing the cauda equina and producing cauda equina syndrome — a surgical emergency characterized by bilateral leg weakness, saddle anesthesia, and loss of bladder or bowel control.

The WHO (2005) document specifies that the risk differential between cervical and lumbar manipulation is significant: serious adverse events following lumbar manipulation are estimated to occur less frequently than those associated with cervical manipulation in documented literature reviewed by that body.

Causal Relationships or Drivers

The causal pathway from cervical spinal manipulation to vertebral artery dissection remains contested in the scientific literature. A key methodological challenge, documented in a 2008 paper by Cassidy et al. published in Spine, is that patients with VAD frequently present with neck pain and headache — the same symptoms that lead patients to seek chiropractic care — before the dissection has been clinically identified. This creates a strong selection bias that complicates attribution.

Three primary driver categories are recognized in the risk literature:

Pre-existing arterial pathology. Connective tissue disorders such as Marfan syndrome, Ehlers-Danlos syndrome (hypermobile type), and fibromuscular dysplasia are established risk multipliers for spontaneous or manipulation-related arterial dissection. These conditions weaken the arterial wall and lower the strain threshold required to initiate a tear.

Technique parameters. Rotational HVLA at end range, particularly when combined with extension, generates the highest documented strain on the vertebral artery. Reduced-force techniques — including flexion-distraction, mobilization, and instrument-assisted adjustment — carry a substantially lower theoretical risk profile for this mechanism. The spinal manipulation vs. spinal mobilization page addresses the biomechanical distinction in detail.

Patient age and comorbidities. Patients over 65 present with higher prevalence of osteoporosis, degenerative joint disease, and vascular calcification — all of which alter the risk-benefit calculation for HVLA techniques, particularly in the cervical spine. The chiropractic for older adults and seniors page provides additional context on age-stratified considerations.

Lumbar cauda equina syndrome from manipulation is considered extremely rare; published case series in the Journal of Manipulative and Physiological Therapeutics (JMPT) document isolated incidents rather than population-level frequencies, and the causal relationship often involves manipulation applied to a patient with an already-symptomatic large disc herniation that was not identified before treatment.

Classification Boundaries

Contraindications to chiropractic spinal manipulation are divided into absolute contraindications (where SMT must not be applied to the affected region) and relative contraindications (where SMT requires modification, additional screening, or is applied at the clinician's informed judgment).

Absolute contraindications as enumerated in the WHO (2005) guidelines include:
- Malignancy of the spine (primary or metastatic)
- Fracture of the segment to be manipulated (acute or unstable)
- Severe osteoporosis (quantified by bone density criteria)
- Acute myelopathy or cord compression
- Infection of the spine (spondylodiscitis, epidural abscess)
- Cauda equina syndrome (active or suspected)
- Significant arteriopathy or known vertebral artery anomaly at the segment targeted

Relative contraindications include conditions where HVLA may be modified or avoided in favor of low-force alternatives:
- Anticoagulant therapy (elevated risk of hematoma formation)
- Spondylolisthesis with neurological deficit
- Inflammatory arthropathies (rheumatoid arthritis, ankylosing spondylitis) at active phase
- Hypermobility syndromes (Marfan, Ehlers-Danlos)
- Pregnancy (for certain techniques and spinal regions; see chiropractic care during pregnancy)
- Acute radiculopathy with progressive neurological deficit

The Federation of Chiropractic Licensing Boards (FCLB) maintains model practice act language that references contraindication assessment as part of the standard of care, aligning with the NBCE competency framework.

Tradeoffs and Tensions

The core tension in chiropractic safety discourse involves the relative risk of SMT versus the relative risk of the alternatives it displaces. Nonsteroidal anti-inflammatory drugs (NSAIDs), the most common pharmacological alternative for acute low back pain, carry a documented risk of gastrointestinal hemorrhage and cardiovascular events at population scale. A Cochrane Review-level body of evidence consistently places minor adverse event rates for chiropractic SMT (primarily soreness, temporary stiffness) in the 33–60% range for transient post-treatment effects, while serious adverse event rates remain low-frequency.

A second tension exists between the precautionary principle and access equity. Aggressive contraindication screening may exclude patients — particularly those with older age, comorbidities, or prior vertebral pathology — from a non-pharmacological therapy that may be their safest available option. This tension is sharpest in geriatric populations where both opioid risk and surgical risk are elevated.

A third contested area involves pre-manipulation screening tests for vertebrobasilar insufficiency. The vertebral artery test (sustained end-range rotation/extension) was historically used to screen for arterial compromise before cervical manipulation. The Australian Physiotherapy Association and the International Federation of Orthopaedic Manipulative Physical Therapists have both published position statements indicating that this test lacks sufficient sensitivity and specificity to reliably identify at-risk patients — meaning a negative test result does not reliably exclude risk.

Common Misconceptions

Misconception: The audible "pop" during adjustment confirms therapeutic effect.
The cavitation sound produced during HVLA manipulation is caused by the collapse of gas bubbles within the synovial fluid of the zygapophyseal joint, a phenomenon documented in imaging studies published in PLOS ONE (2015). The presence or absence of the sound does not correlate with clinical outcome or with the magnitude of force applied.

Misconception: Chiropractic adjustment always causes serious strokes.
Absolute serious adverse event rates from cervical manipulation are estimated in the published literature at figures ranging from 1 in 400,000 to 1 in several million manipulations, though methodological debate around these figures persists. The WHO (2005) explicitly states that serious complications are "rare" and that the risk is "low when manipulation is applied correctly."

Misconception: All chiropractic techniques carry equal risk.
Force magnitude, vector, and velocity differ substantially across technique families. The cox flexion-distraction technique applies sustained low-force distraction rather than HVLA thrust, carrying a materially different tissue-loading profile than rotational cervical manipulation.

Misconception: Contraindications only apply to the spine.
The extremity joints — shoulder, knee, ankle — are also adjusted in chiropractic practice and carry distinct contraindication sets, including acute fracture, joint replacement hardware, and active inflammatory flare at the target joint.

Checklist or Steps (Non-Advisory)

The following is a structural representation of the pre-manipulation safety screening sequence as described in NBCE clinical competency standards and WHO (2005) guidelines. This is a reference description of the clinical process, not a care recommendation.

Pre-Manipulation Safety Screening Sequence

1. Chief complaint and history intake — Document the site, onset, character, and progression of symptoms; identify red flag symptoms (bowel/bladder changes, progressive neurological deficit, unexplained weight loss, fever, prior malignancy history).
2. Medication and medical history review — Screen for anticoagulant use, corticosteroid history (osteoporosis risk), and known connective tissue disorders.
3. Orthopedic and neurological examination — Assess motor strength, sensation, deep tendon reflexes, and orthopedic provocation tests relevant to the region of complaint.
4. Imaging review (when indicated) — Evaluate existing radiographs, MRI, or CT for fracture, neoplasm, severe disc herniation, or bony anomaly. The chiropractic x-ray and diagnostic imaging page describes when imaging is indicated.
5. Contraindication determination — Classify identified findings as absolute contraindications, relative contraindications requiring technique modification, or no contraindication.
6. Informed consent — Disclose known risks, including the low-frequency risk of serious adverse events. Documentation of consent is a standard-of-care requirement in most state licensing frameworks.
7. Technique selection — Select manipulative method based on contraindication profile, patient tolerance, and clinical objective.
8. Post-treatment monitoring — Assess patient response immediately post-adjustment; document any adverse reactions per clinical record standards.

Reference Table or Matrix

Chiropractic Contraindication Classification Matrix

Sources: WHO Guidelines on Basic Training and Safety in Chiropractic (2005); NBCE Clinical Competency Frameworks; Federation of Chiropractic Licensing Boards Model Practice Act.

References

• World Health Organization — WHO Guidelines on Basic Training and Safety in Chiropractic (2005)
• National Board of Chiropractic Examiners (NBCE)
• Federation of Chiropractic Licensing Boards (FCLB)
• National Institutes of Health — PubMed / National Library of Medicine
• American Chiropractic Association — Safety and Patient Information
• Journal of Manipulative and Physiological Therapeutics (JMPT) — NIH-indexed archive
• Cassidy JD et al., "Risk of Vertebrobasilar Stroke and Chiropractic Care," Spine, 2008 — PubMed