A chiropractic adjustment, formally known as Spinal Manipulative Therapy (SMT), is a procedure where a practitioner applies a controlled, high-velocity, low-amplitude thrust to a specific joint, most often in the spine. The procedure is intended to restore joint mobility, reduce pain, and improve function. As with any medical intervention, the question of safety is paramount and subject to extensive scientific research. Examining the evidence distinguishes between minor, expected reactions and extremely rare, severe complications to provide an accurate safety profile.
Common Side Effects Versus Serious Adverse Events
The majority of adverse reactions following a chiropractic adjustment are minor and temporary, falling into the category of common side effects. These transient, self-limiting symptoms are reported by 50% to 67% of patients following SMT. Reactions frequently include temporary soreness, stiffness, or an increase in the presenting pain. These effects typically occur within an hour of treatment and resolve completely within 24 to 48 hours, representing a normal musculoskeletal response to the physical intervention.
In contrast, serious adverse events (SAEs) are severe, life-threatening, or result in permanent disability, and they are statistically rare. The most discussed SAE associated with neck manipulation is vertebral artery dissection (VAD), a tear in the inner lining of an artery that can lead to a stroke. The estimated incidence rate of VAD following a cervical adjustment is extremely low, ranging from approximately 1 in 20,000 manipulations to less than 1 in 1 million manipulations. Researchers debate whether the adjustment causes the dissection or if patients already experiencing a spontaneously developing dissection seek treatment, creating an association rather than causation.
For the lower back, the most documented SAEs are cauda equina syndrome (CES) and lumbar disc herniation, which are exceedingly rare events. CES involves severe compression of the spinal nerve roots, requiring immediate surgical intervention. A systematic review of lumbopelvic SMT cases identified CES and disc herniation as the most frequent serious events reported. However, the anecdotal nature of case studies makes it difficult to establish a definitive causal link. The overall risk of a serious event is considered negligible when compared with other common treatments for musculoskeletal pain, such as nonsteroidal anti-inflammatory drugs (NSAIDs) or surgery.
Identifying and Managing Contraindications
Safety in SMT is highly dependent on a practitioner’s ability to appropriately screen patients and identify pre-existing conditions that make the procedure unsafe. A thorough patient history and physical examination are the primary mechanisms used to mitigate risk before any adjustment is performed. This screening process identifies absolute contraindications, which are conditions where a high-velocity thrust should never be applied.
Absolute contraindications include acute spinal fractures, active infections of the bone or joint like osteomyelitis, and spinal tumors or metastasis. Conditions that severely compromise spinal integrity, such as advanced osteoporosis, spinal cord compression, or acute inflammatory arthritis affecting the cervical spine, prohibit high-velocity manipulation due to the risk of fracture or neurological injury. Identifying these conditions ensures that patients are either referred for other forms of medical care or managed using gentle, low-force techniques.
Other conditions are considered relative contraindications, meaning an adjustment may still be possible but requires extreme caution and significant modification of the technique. Examples include moderate osteoporosis, known disc herniations without progressive neurological deficit, or patients undergoing anticoagulant therapy. In these cases, the practitioner must weigh the risk-benefit ratio and may choose to use alternative treatments, such as soft tissue therapy or gentle mobilization. The core safety principle is that any signs of instability, infection, or severe neurological compromise must be recognized and respected to prevent complications.
Risk Profile Based on Spinal Region
The risk profile of an adjustment varies significantly depending on the region of the spine being treated, primarily due to anatomical differences. The cervical spine, or neck, carries the most scrutiny regarding safety because of the close proximity of the vertebral arteries. These arteries travel through the transverse processes of the cervical vertebrae to supply blood to the brainstem and cerebellum, forming the vertebrobasilar system.
A forceful, rotatory adjustment in the neck has the theoretical potential to mechanically stress or injure an already weakened vertebral artery, potentially causing a dissection. This mechanism is linked to the rare instances of stroke following cervical manipulation. The American Heart Association has noted the need to inform patients of a potential association between cervical manipulative therapy and cervical dissection prior to manipulation.
In contrast, adjustments to the thoracic spine (mid-back) and lumbar spine (lower back) are associated with a lower risk of serious vascular complications. The primary concern in the lower spine is related to disc injuries, such as a worsening disc herniation or cauda equina syndrome. While still rare, these lower back complications involve mechanical injury to the spinal structures or nerves, rather than the vascular concerns prominent in the neck. The difference in risk reflects the distinct anatomy of the vertebral canal and surrounding vascular structures in each spinal region.
Professional Training and Licensing Standards
The safety of a chiropractic adjustment is linked to the competency and extensive training of the practitioner delivering the care. To become a licensed Doctor of Chiropractic (D.C.) in regulated jurisdictions, a candidate must complete a rigorous educational pathway. This typically requires a minimum of three years of undergraduate pre-professional college education, followed by a four-year Doctor of Chiropractic degree program from an accredited institution.
The D.C. curriculum is comprehensive, involving extensive hours of classroom and clinical instruction that often totals over 4,200 hours, comparable to other doctoral-level medical education programs. Coursework focuses heavily on fundamental medical sciences, including anatomy, physiology, pathology, and advanced clinical skills such as diagnosis, radiology, and differential diagnosis. These diagnostic skills enable the practitioner to identify the contraindications and underlying pathologies that would make SMT unsafe for a patient.
Licensure is granted only after the candidate successfully passes all parts of the standardized national examinations administered by the National Board of Chiropractic Examiners (NBCE). These boards test knowledge across basic sciences, clinical sciences, and practical skills, including adjusting techniques and case management. Seeking care from a licensed professional who adheres to these rigorous standards is the patient’s most reliable measure of safety.