Spinal Deviations

Populations and Risk Factors

• Adolescents during growth spurts — the period of peak height velocity is the highest-risk window for scoliosis progression and Scheuermann's disease onset; skeletal immaturity means the spine is still malleable and susceptible to deformation
• Postmenopausal women with osteoporosis — vertebral compression fractures produce progressive structural kyphosis; one compression fracture increases the risk of subsequent adjacent fractures 5-fold
• Individuals with neuromuscular conditions — cerebral palsy, muscular dystrophy, Parkinson's disease, poliomyelitis all produce spinal deviations through trunk muscle imbalance, spasticity, or paralysis
• Individuals with chronic postural imbalances — upper crossed syndrome drives kyphosis; lower crossed syndrome drives lordosis; combined "layer syndrome" affects the entire spine
• Leg-length discrepancy (true or functional) — even a 5 mm discrepancy can produce a compensatory lumbar scoliosis that becomes structural over time
• Ankylosing spondylitis — progressive inflammatory spinal fusion eliminates spinal curves and locks the spine in a fixed, deviated position
• Congenital vertebral anomalies — hemivertebrae, failure of segmentation, or vertebral bars produce structural deviations from birth
• Family history: scoliosis has a significant genetic component; first-degree relatives of individuals with AIS have a 10-fold increased risk

Causes and Pathophysiology

Sagittal Plane Deviations (Kyphosis/Lordosis)

• Normal sagittal alignment: The spine has four physiological curves: cervical lordosis (~20–40 degrees), thoracic kyphosis (~20–45 degrees), lumbar lordosis (~40–60 degrees), and sacral kyphosis (fixed). These curves develop sequentially — the thoracic and sacral curves are primary (present at birth), while the cervical and lumbar curves are secondary (develop with head control and walking). Together, they position the body's center of gravity over the base of support and distribute compressive forces efficiently. The curves act as a spring mechanism: the Euler column buckling equation predicts that a column with N curves can withstand (N squared + 1) times more load than a straight column — a spine with three mobile curves withstands 10 times more force.

• Hyperkyphosis (excessive thoracic curve): Thoracic kyphosis beyond 45 degrees. Functional causes involve anterior soft tissue shortening (pectorals, anterior intercostals) and posterior extensor weakness/inhibition (thoracic erector spinae, lower trapezius) — the thoracic component of upper crossed syndrome. Structural causes involve vertebral body wedging from Scheuermann's disease (developmental endplate irregularity during growth) or osteoporotic compression fractures (bone density loss leading to anterior vertebral collapse). The key pathophysiological consequence is respiratory compromise: increased kyphosis reduces rib cage anteroposterior diameter, displaces the diaphragm, and reduces vital capacity by approximately 9% per 10 degrees of additional curvature. See hyperkyphosis for full detail.

• Hyperlordosis (excessive lumbar curve): Lumbar lordosis beyond 60 degrees. Most commonly driven by lower crossed syndrome — hypertonic iliopsoas and erector spinae creating anterior pelvic tilt. The key pathophysiological consequence is posterior element overloading: as lordosis increases, weight-bearing shifts from balanced distribution to predominantly posterior, loading the facet joints (up to 40–50% of axial load) and narrowing the intervertebral foramina. This explains the extension-provocative pain pattern and the association with facet syndrome and spondylolisthesis. See hyperlordosis for full detail.

• Hypolordosis (reduced lumbar curve): Lumbar lordosis below 40 degrees or absent. Driven by hamstring dominance and posterior pelvic tilt (inverse of LCS) or by structural causes (ankylosing spondylitis, post-surgical fusion). The key pathophysiological consequence is anterior compressive overloading: axial forces concentrate on the anterior vertebral bodies and disc, reducing shock absorption capacity. A flat spine withstands only 1/10th the compressive force of a normally curved spine. See hypolordosis for full detail.

Coronal Plane Deviations (Scoliosis)

• Scoliosis mechanism: Lateral spinal curvature of 10 degrees or more (measured by Cobb angle on radiography) with accompanying vertebral rotation. The rotation distinguishes scoliosis from simple lateral bending — the vertebral bodies rotate toward the convexity while the spinous processes rotate toward the concavity. This rotation produces the rib hump visible on Adam's forward bend test. Adolescent idiopathic scoliosis (AIS) accounts for approximately 80% of all scoliosis cases, with a strong female predominance (7–10:1) during the growth spurt years.

• Functional vs. structural distinction: Functional scoliosis is caused by external factors (muscle spasm, leg-length discrepancy, protective guarding) — the spine itself is structurally normal. On Adam's forward bend test, the lateral curve straightens and no rib hump appears. Structural scoliosis involves fixed vertebral rotation and bony adaptation — on forward bending, the curve persists and a rib hump is visible on the convex side. This distinction determines treatment approach: functional scoliosis is potentially fully correctable by addressing the underlying cause; structural scoliosis is managed for symptom relief and progression prevention, not cure.

• Convex/concave muscle pattern: On the concave side of a scoliotic curve, the muscles are shortened, hypertonic, and often fibrotic — they are chronically contracted to maintain the deviation. On the convex side, the muscles are elongated, weakened, and often inhibited — they are chronically stretched beyond their optimal length-tension relationship. This pattern is clinically critical because it determines treatment targeting: the concave side requires release and lengthening; the convex side requires facilitation and strengthening. Treating both sides identically will be ineffective.

Combined and Compensatory Patterns

• Compensatory curve chains: Spinal deviations rarely exist in isolation. A primary kyphosis produces compensatory cervical and lumbar hyperlordosis to maintain the gaze horizontal and the center of gravity over the base of support. A primary lumbar scoliosis produces a compensatory thoracic scoliosis in the opposite direction to balance the head over the pelvis. These compensatory curves are initially functional but can become structural over time as the soft tissues and bony structures adapt to the deviated position. Clinically, the primary curve must be identified and treated first; treating a compensatory curve without addressing the primary deviation will destabilize the compensation without resolving the root cause.

• Combined sagittal and coronal deviations: Patients frequently present with deviations in multiple planes — for example, thoracic kyphosis with lumbar scoliosis, or hyperlordosis with thoracic scoliosis. The three-dimensional nature of spinal deviation means that sagittal plane assessment alone is insufficient — both sagittal (lateral profile) and coronal (posterior profile) planes must be assessed, along with rotation (Adam's forward bend test). The plumb line assessment evaluates both planes simultaneously.

• Panjabi's three-subsystem model: Spinal stability depends on three interdependent subsystems: (1) the passive subsystem (bones, ligaments, discs, facet joints — provides structural constraint); (2) the active subsystem (muscles — provides dynamic stabilization); (3) the neural control subsystem (proprioceptors, CNS integration — coordinates the active subsystem). Spinal deviations represent failure in one or more subsystems: postural/functional deviations primarily involve the active and neural control subsystems (muscle imbalance, poor motor control); structural deviations involve the passive subsystem (bony deformity, ligamentous adaptation); neuromuscular deviations involve all three. Treatment must address all affected subsystems for lasting correction.

Signs and Symptoms

By Deviation Type

General Symptoms Across All Deviations

• Chronic dull ache and muscular tension in the deviated region
• Loss of spinal ROM — restricted in the direction that would correct the deviation
• Fatigue — maintaining an abnormal spinal position requires constant muscular effort
• Progressive loss of height with structural deviations (compression fractures, disc narrowing)
• Respiratory compromise — thoracic deviations (kyphosis >60 degrees, thoracic scoliosis >40 degrees) reduce vital capacity

Severity Indicators

• Mild: cosmetic concern and mild discomfort; no functional limitation; no respiratory compromise
• Moderate: persistent pain; ROM limitation; early respiratory compromise measurable on chest expansion
• Severe: significant respiratory and/or cardiac compromise; neurological involvement possible; structural deformity visible at rest

Assessment Profile

Subjective Presentation

• Chief complaint: Variable depending on the deviation — may present with the postural concern itself ("my back is curved"), with secondary pain (neck pain from cervical compensation, low back pain from lumbar loading), or with functional limitation (reduced breathing capacity, inability to stand upright)
• Pain quality: Dull, aching, diffuse in postural deviations; sharp, localized at the apex of structural curves; may be absent in mild deviations that are identified incidentally
• Onset: Postural: insidious, developing over months to years; Scheuermann's/AIS: noticed during adolescent growth spurt; osteoporotic: may be sudden (compression fracture event) superimposed on gradual progression; neuromuscular: progressive with the underlying condition
• Aggravating factors: Sustained postures, prolonged standing or sitting, activities that load the deviated curve (extension for kyphosis, extension for lordosis, lateral loading for scoliosis)
• Easing factors: Position change, movement, correction of the primary driver (e.g., heel lift for leg-length discrepancy), warmth
• Red flags: Rapidly progressive curvature in an adolescent (referral for orthopedic monitoring); sudden severe localized thoracic pain in a patient with osteoporosis risk (compression fracture — medical referral for imaging); bilateral leg weakness, saddle anesthesia, or bladder/bowel dysfunction (cauda equina — emergency referral; do not treat); suspected spinal malignancy (unrelenting pain worse at night, weight loss, previous cancer history — medical referral)

Observation

• Local inspection: Assess from posterior (shoulder height symmetry, scapular position, waistline symmetry, iliac crest height, gluteal fold symmetry) and lateral (cervical lordosis, thoracic kyphosis, lumbar lordosis, pelvic tilt) views; document visible deviations; inspect for rib hump during Adam's forward bend; measure height and compare to previous records; assess leg-length discrepancy visually (iliac crest height) and by measurement if suspected
• Posture: Full plumb line assessment — lateral: external auditory meatus should align vertically with the acromion, greater trochanter, lateral knee joint line, and lateral malleolus; posterior: mastoid processes, shoulder heights, inferior scapular angles, iliac crests, PSIS, gluteal folds, and medial malleoli should be bilaterally symmetric; deviations from plumb line in either view indicate the plane and direction of the deviation
• Gait: Trendelenburg gait indicates gluteus medius weakness (LCS/hyperlordosis); lateral trunk sway suggests scoliosis compensation; reduced arm swing suggests thoracic rigidity; shuffling gait in elderly patients may indicate global spinal stiffness

Palpation

• Tone: Assess bilaterally and compare: in scoliosis, the concave side muscles are shortened and hypertonic while the convex side muscles are elongated and hypotonic; in kyphosis, anterior muscles are shortened (pectorals) and posterior muscles may be overstretched; in lordosis, extensors are hypertonic and abdominals are hypotonic; in hypolordosis, hamstrings are dominant and extensors are inhibited. The specific tonal pattern identifies the deviation type and guides treatment targeting
• Tenderness: Spinous process palpation along the entire spine to identify the apex of curvature and any segmental hypomobility; costovertebral joint tenderness (thoracic deviations); paraspinal tenderness concentrated at the deviation apex; in scoliosis, the concave side muscles are typically more tender (shortened, fibrotic) while the convex side is less tender (stretched, inhibited)
• Temperature: Usually normal; localized warmth at a specific segment may indicate acute fracture, active inflammation (ankylosing spondylitis), or facet irritation
• Tissue quality: Assess paraspinal tissue bilaterally for asymmetry: in scoliosis, the concave side is dense, fibrotic, and shows reduced fascial mobility; the convex side is thin, elongated, and poorly toned; in kyphosis, the thoracic extensors may be thin and atrophied while the pectorals are dense and shortened; in lordosis, the lumbar erectors are dense and ropy while the abdominals are soft; costovertebral stiffness (reduced rib spring) in thoracic deviations reflects the costovertebral adaptation mechanism

Motion Assessment

• AROM: Assess all spinal movements (flexion, extension, bilateral lateral flexion, bilateral rotation) and compare: deviations restrict motion in the direction that would correct the curve — kyphosis restricts extension; lordosis restricts flexion (or extension is provocative); hypolordosis restricts extension; scoliosis restricts lateral flexion toward the convexity and rotation; the pattern of restriction identifies the deviation; assess whether the curve corrects with active effort (functional) or remains fixed (structural)
• PROM / end-feel: Firm tissue stretch end-feel indicates soft tissue restriction (potentially correctable); hard/bony end-feel indicates structural bone deformity (not correctable with manual therapy); empty end-feel (pain prevents full testing) may indicate fracture or severe inflammation; rib spring testing (bilateral comparison) assesses costovertebral mobility in thoracic deviations
• Resisted testing: Test trunk extensors, flexors, and lateral flexors for bilateral symmetry; weakness on the elongated side and strength on the shortened side of a curve confirms the muscle imbalance pattern; specific muscle testing depends on the deviation type (see individual condition articles)

Special Test Cluster

If scoliosis is identified: determine if primary or compensatory; check for leg-length discrepancy (if equalizing leg length corrects the scoliosis, the scoliosis is functional and secondary to the discrepancy). If thoracic deviation with osteoporosis risk: avoid aggressive testing; refer for bone density assessment.

Differential Assessment