Spine and Pelvis Range of Motion

1. High-Yield Summary

Evaluation of spine and pelvis range of motion (ROM) isolates segmental mobility across the axial skeleton while decoupling true spinal excursion from pelvic rotation and coxofemoral kinematics across dynamic postural transitions:

• Primary Diagnostic Objective: To systematically quantify regional mobility (cervical, thoracic, lumbar) and evaluate dynamic spinopelvic-coxofemoral kinematic coupling, differentiating structural axial stiffness (ankylosing spondylitis, surgical arthrodesis, diffuse idiopathic skeletal hyperostosis) from pelvic rotation and hamstring contracture.
• Pathognomonic Physical Findings: Quantitative restriction of lumbar forward flexion (<4.0 cm expansion on the Modified Schober Test, <50° true lumbar flexion on dual inclinometry); absence of caudal descent of the posterior superior iliac spine (PSIS) on the Gillet/Stork test indicating sacroiliac hypomobility; and discordance between standing and seated forward bend highlighting hamstring tethering.
• Statistical Accuracy Benchmarks: The Modified Schober Test achieves a sensitivity of 88% and specificity of 86% for structural lumbar hypomobility; Dual Inclinometry demonstrates a sensitivity of 89% and specificity of 91% against radiographic gold standards; Standing versus seated forward bend decoupling yields a sensitivity of 91% and specificity of 93% for distinguishing isolated hamstring contracture from true lumbar ankylosis.
• Primary Diagnostic Pitfall: Hamstring tightness anchors the ischial tuberosities in standing, artificially limiting forward reach (finger-to-floor distance) and falsely mimicking structural spine rigidity; seated forward flexion eliminates hamstring tension and immediately exposes true spinal excursion.
• Spinopelvic Mobility Phenotyping: Differentiating the “stuck standing” phenotype (rigid lordosis with low pelvic tilt, creating severe seated posterior hip dislocation risk) from the “stuck sitting” phenotype (rigid flatback with high pelvic tilt, creating standing anterior hip dislocation risk) is essential prior to total hip arthroplasty.

2. Clinical Indications & Target Pathology

Assessment of spine and pelvis range of motion is indicated across several clinical scenarios where axial symptoms, spinal deformity, and lower extremity mechanics overlap:

• Screening for Axial Spondyloarthritis and Seronegative Arthropathies: Young to middle-aged adults presenting with insidious, inflammatory low back pain, morning stiffness exceeding 30 minutes, buttock pain alternating between sides, and symptom improvement with activity rather than rest. Serial measurement of lumbar and thoracic excursion provides objective monitoring of disease progression and response to biologic therapy.
• Preoperative Total Hip Arthroplasty (THA) Risk Stratification: Quantifying dynamic spinopelvic mobility is critical to prevent post-arthroplasty instability. Patients with a stiff spinopelvic complex (ΔSS < 10° between standing and sitting) exhibit a three-fold to seven-fold increase in dislocation rates when managed with traditional static acetabular component targets.
• Adult Spinal Deformity (ASD) and Sagittal Imbalance Evaluation: Patients presenting with flatback syndrome, anterior trunk tilt, crouched gait, and severe paraspinal muscle fatigue secondary to progressive loss of lumbar lordosis. Range of motion testing defines whether deformity is flexible or fixed.
• Disentangling Hip-Spine Syndrome: Differentiating true coxofemoral pathology (groin pain, restricted internal rotation, positive FADIR test) from lumbar radiculopathy or spinal stenosis (buttock and posterior thigh radiation, neurogenic claudication, dermatomal deficits) and sacroiliac joint dysfunction.
• Diffuse Idiopathic Skeletal Hyperostosis (DISH) and Ankylosing Conditions: Older adults presenting with progressive global axial stiffness, dysphagia from anterior cervical osteophytes, or chalk-stick fracture vulnerability following low-energy trauma.
• Postoperative Arthrodesis Surveillance: Functional assessment of patients with prior instrumented spinal fusion to evaluate adjacent segment hypermobility or mechanical stress concentration at the sacroiliac and coxofemoral joints.

3. Functional Anatomy & Biomechanical Mechanism

The axial skeleton and pelvis function as a closed, reciprocal kinematic chain. Motion occurs through specialized multi-axial articulations coordinated across distinct spinal regions:

• Cervical Spine Motion Segments: The craniocervical junction possesses specialized kinematics: the occipitoatlantal (C0-C1) articulation accommodates approximately 50% of total cervical flexion-extension (20° to 30° arc), governed by the cup-shaped superior articular facets of C1. The atlantoaxial (C1-C2) pivot articulation accommodates approximately 50% of total cervical axial rotation (40° to 45° to each side), centered on the odontoid process. The subaxial cervical spine (C3-C7) provides the remaining sagittal flexion-extension and coupled lateral bending/rotation, dictated by articular facets oriented at 45° to the transverse plane.
• Thoracic Spine and Rib Cage Restraint: The thoracic motion segments are inherently rigid due to the stabilizing framework of the costovertebral and costotransverse joints attached to the sternal cage. Thoracic facet joints are oriented in the coronal plane, which facilitates axial rotation (approximately 30° to 35° total thoracic rotation) but strongly restricts sagittal flexion-extension and lateral bending, protecting thoracic viscera and maintaining a stable thoracic kyphosis.
• Lumbar Facet Architecture and Segmental Constraints: Lumbar facet joints from L1 to L4 are oriented primarily in the sagittal plane. This orientation accommodates substantial flexion (40° to 60°) and extension (20° to 35°) while mechanically blocking axial rotation (limited to less than 5° to 10° across the entire lumbar spine). At L5-S1, the facet joint transitions abruptly to the coronal plane, providing critical bony resistance against anterior gravitational shear forces.
• The Spinopelvic Invariant Identity (PI = PT + SS): Spatial pelvic orientation is governed by the invariant geometric law established by Duval-Beaupère and Legaye: Pelvic Incidence (PI) = Pelvic Tilt (PT) + Sacral Slope (SS). Pelvic Incidence is an immutable morphological constant fixed upon physeal closure, reflecting the spatial width and shape of the pelvis. Sacral Slope (inclination of the S1 endplate to the horizontal) and Pelvic Tilt (spatial rotation around the femoral heads relative to vertical) are dynamic reciprocal positional angles. Any reduction in sacral slope produces an equal, obligatory increase in pelvic tilt (ΔPT = -ΔSS).
• Normal Standing-to-Sitting Kinematics and Dynamic Cup Anteversion: Moving from standing to relaxed slump-sitting requires 90° of torso-thigh flexion. In healthy individuals, this arc is shared: 20° is accommodated by pelvic retroversion (mediated by lumbar flexion shedding 20° to 30° of lordosis, with sacral slope decreasing by 20° and pelvic tilt increasing by 20°), while the remaining 70° is accommodated by true coxofemoral joint flexion. Because the acetabulum is rigidly embedded within the innominate bone, every 1° of posterior pelvic tilt dynamically increases functional acetabular anteversion by 0.7° and functional inclination by 0.5°. This normal 20° pelvic retroversion adds 12° to 15° of functional anteversion, opening the anterior acetabular rim to clear the anterior femoral neck during seated hip flexion.
• Pathomechanics of Spinopelvic Stiffness: Loss of dynamic spinopelvic mobility (ΔSS 20°), the pelvis cannot antevert during standing, locking the cup in excessive functional anteversion and vertical inclination, triggering standing posterior impingement and anterior dislocation during terminal hip extension.

4. Step-by-Step Examination Technique

Patient Positioning

Precision execution requires standardized patient positioning across standing, seated, and supine postures to systematically decouple regional biomechanical contributors:

• Upright Standing Assessment: The patient is barefoot, disrobed appropriately to expose the entire spinal column, pelvic dimples, and lower extremities. Feet are positioned shoulder-width apart (approximately 15 cm intermalleolar distance), with knees fully extended without hyperextension. Arms rest naturally at the sides. The examiner verifies that the floor is level and that any true leg length discrepancy is compensated with calibrated foot blocks under the short limb to eliminate pelvic obliquity.
• Slump-Seated Decoupling Setup: The patient sits on an armless, backless examination stool with thighs horizontal (parallel to the floor) and knees flexed to 90°. Feet rest flat on the floor or foot support. This posture stabilizes the pelvis, locks the ischial tuberosities onto the bench, and completely slackens the hamstring musculature, removing hamstring tension as a confounder.
• Supine and Prone Table Setup: A rigid, flat examination table is utilized for passive hip range of motion testing, contracture identification (Thomas test), popliteal angle measurement, and provocative sacroiliac maneuvers.

Examiner Hand Placement & Setup

Accurate palpation and instrument calibration are mandatory prior to initiating provocative maneuvers:

• Landmarking the Posterior Superior Iliac Spines (PSIS): The examiner sits or kneels behind the standing patient with eye level aligned with the lumbosacral junction. Bilateral thumbs firmly locate the inferior osseous contours of the PSIS, visible as the cutaneous “dimples of Venus.” A horizontal line connecting the bilateral PSIS marks the second sacral vertebral level (S2).
• Landmarking the Lumbosacral and Thoracolumbar Junctions: The intercristal line (Tuffier’s line) connecting the superior apices of the iliac crests identifies the L4-L5 interspace. The L5-S1 junction is palpated directly below. The T12-L1 interspinous space is localized by tracing the 12th rib cephalad to its costovertebral articulation.
• Instrumentation Placement and Calibration: For tape measurement, a flexible, non-elastic metric tape is held flush against the skin contour. For dual inclinometry, digital inclinometers are positioned firmly over the T12-L1 spinous interspace (cranial sensor) and the S1-S2 sacral base (caudal sensor), and zeroed in the patient’s neutral upright standing posture.

Provocative Maneuver Execution

Provocative examination proceeds systematically through active cervical, thoracic, and lumbar arcs, followed by validated quantitative maneuvers and hip-spine decoupling:

• Active Cervical Spine ROM:
  1. Flexion and Extension: The patient actively flexes forward attempting to touch the chin to the chest (normal: 45° to 50°). The patient then extends backward gazing directly toward the ceiling (normal: 55° to 60°).
  2. Lateral Bending: The patient bends the neck laterally, bringing each ear toward the ipsilateral acromion without elevating the shoulder girdle (normal: 40° to 45° bilaterally).
  3. Axial Rotation: The patient rotates the head to look over each shoulder, aligning the chin with the clavicle (normal: 70° to 80° bilaterally). Inclinometry over the vertex provides objective degree measurements.
• Active Thoracic and Lumbar Global ROM:
  1. Thoracolumbar Rotation: The patient sits on the stool with arms crossed over the chest to eliminate pelvic rotation. The patient actively twists the upper body to each side (normal: 30° to 40° bilaterally, reflecting isolated thoracic excursion).
  2. Lateral Flexion: Standing erect, the patient slides the palm down the lateral aspect of the thigh without rotating the trunk or flexing the knees (normal: 25° to 35° bilaterally).
  3. Gross Standing Flexion (Finger-to-Floor Distance): The patient bends forward at the waist with knees locked in full extension. The vertical distance between the tip of the middle finger and the floor is measured with a rigid ruler (normal: 0 to 5 cm; >10 cm indicates significant restriction).
• The Modified Schober Test (MST) Execution:
  1. With the patient standing erect and knees locked in full extension, the examiner identifies the horizontal line connecting the PSIS (S2 level) or the lumbosacral junction (S1).
  2. A skin mark is drawn at this midline baseline point. A second mark is placed exactly 10 cm superiorly along the midline spine. In the classic Modified Schober method, a third mark is placed 5 cm inferiorly, establishing a 15 cm baseline span.
  3. The patient performs slow, maximal active forward flexion with knees kept strictly locked in full extension.
  4. The examiner maintains the flexible tape against the skin contour and records the distracted distance between the cutaneous marks at maximal forward bend.
  5. Interpretation: An increase of ≥5.0 cm (total span ≥20.0 cm from a 15 cm baseline, or ≥15.0 cm from a 10 cm baseline) indicates normal lumbar excursion. An expansion of <4.0 cm confirms structural lumbar hypomobility.
• Dual Inclinometry (AMA Guides Method):
  1. Inclinometer 1 is positioned over the T12-L1 interspinous space; Inclinometer 2 is positioned over the S1-S2 junction. Both sensors are zeroed in neutral standing.
  2. The patient bends forward maximally into full flexion with knees straight.
  3. The examiner reads both sensors simultaneously: the T12 sensor records gross thoracolumbar flexion (normal: 100° to 110°); the S1 sensor records pelvic (sacral/hip) flexion (normal: 50° to 60°).
  4. True Lumbar Flexion Calculation: True Lumbar Flexion = T12 Angle – S1 Angle (normal: ≥60°; pathological: <40° to 50°).
  5. True Lumbar Extension: The patient extends backward maximally. True Lumbar Extension = T12 Extension Angle – S1 Extension Angle (normal: ≥25°; pathological: <15°).
• Gillet / Stork Sacroiliac Mobility Test:
  1. The patient stands erect facing a wall or rail for balance assistance, feet positioned 15 cm apart. The examiner sits or kneels directly behind.
  2. The examiner places one thumb firmly over the median sacral crest / S2 spinous process and the other thumb over the ipsilateral PSIS.
  3. The patient is instructed to actively flex the ipsilateral hip and knee to 90° or higher, standing on the contralateral extremity.
  4. Normal Mobility Response: The ipsilateral PSIS rotates posteriorly and descends caudally 1 to 2 cm relative to the static sacrum (palpable inferior “drop” of the examiner’s PSIS thumb).
  5. Positive / Pathological Response: The ipsilateral PSIS fails to descend caudally, remains stationary, or paradoxically migrates cephalad along with the sacrum, confirming sacroiliac joint hypomobility, intra-articular locking, or ankylosis. The maneuver is repeated bilaterally.
• Standing versus Seated Hip-Spine Decoupling Maneuver:
  1. The examiner observes the patient during standing forward flexion, noting whether the lumbar spine reverses its lordosis to form a smooth convex curve, and records the fingertip-to-floor distance.
  2. The patient is transitioned to the seated position on the firm examination stool with knees and hips flexed to 90° and feet flat on the floor.
  3. The patient is asked to bend forward slowly, bringing the chest toward the thighs.
  4. Decoupling Analysis: If the patient had severe standing restriction (e.g., finger-to-floor >20 cm) but demonstrates effortless, smooth forward flexion and brings the chest to the thighs when seated, the restriction was caused entirely by tight hamstrings tethering the pelvis. If the lumbar spine remains rigid, flat, and unable to flex during both standing and seated maneuvers, true structural axial ankylosis is confirmed.

5. Positive Test Criteria & Interpretation

Positive criteria are stratified by validated quantitative metric thresholds, dynamic angular excursions, and pathognomonic visual or tactile findings:

• Modified Schober Test (MST) Quantitative Thresholds:
  – Normal Mobility: Excursion ≥5.0 cm (total distance ≥20.0 cm from a 15 cm baseline, or ≥15.0 cm from a 10 cm baseline).
  – Borderline / Mild Restriction: Excursion between 4.0 cm and 4.9 cm.
  – Positive / Pathological Ankylosis: Excursion <4.0 cm (total distance <14.0 cm from a 15 cm baseline). Reflects structural lumbar stiffness pathognomonic of axial spondyloarthritis, severe multi-segmental spondylosis, or surgical fusion.
• Dual Inclinometry Quantitative Thresholds (AMA Impairment Standards):
  – True Lumbar Flexion: Normal is ≥60°. Mild impairment: 40° to 59°. Moderate/Severe structural impairment: <40°.
  – Pelvic / Sacral Flexion: Normal is 50° to 65°. Pelvic hypomobility: 70°.
  – True Lumbar Extension: Normal is ≥25°. Severe restriction: <15°.
• Stefl Spinopelvic Mobility Classification (Dynamic Sacral Slope Excursion: ΔSS = SS_standing – SS_sitting):
  – Normal Spinopelvic Mobility (ΔSS 10° to 30°): In transitioning from standing to sitting, the sacral slope decreases by 10° to 30° (mean ~20°), and the pelvis retroverts reciprocally (ΔPT ~ +20°), increasing functional acetabular anteversion by 12° to 15°.
  – Stiff Spinopelvic Complex (ΔSS < 10°): Pelvic excursion is frozen. Subdivided into:
    • “Stuck Standing” (Rigid Lordosis / Standing PT < 13°): Pelvis fails to retrovert when sitting. Functional cup remains retroverted; seated hip flexion produces anterior neck-cup impingement and posterior dislocation.
    • “Stuck Sitting” (Rigid Flatback / Standing PT > 20°): Pelvis locked in permanent retroversion. Functional cup remains excessively anteverted and vertical when standing; hip extension produces posterior neck-cup impingement and anterior dislocation.
  – Hypermobile Spinopelvic Complex (ΔSS > 30°): Exaggerated dynamic shifts create dual instability (posterior dislocation seated, anterior dislocation standing).
• Tactile and Palpable Endpoints:
  – Gillet Test: Absence of palpable inferior excursion or paradoxical cephalad elevation of the PSIS during hip flexion confirms mechanical restriction of the sacroiliac joint.
  – Thoracolumbar Contour: Absence of normal lordotic reversal during standing forward bend (lumbar spine remains persistently lordotic or flat without forming a smooth dorsal convexity) visually confirms structural axial rigidity.

6. Diagnostic Accuracy & Statistical Benchmarks

The following statistical benchmarks summarize validated diagnostic accuracy metrics extracted from peer-reviewed clinical trials and comparative radiographic investigations:

7. Confounders, Diagnostic Traps & False Results

Accurate interpretation of spine and pelvis mobility requires clinical awareness of common mechanical confounders and compensatory maneuvers:

• Hamstring Tightness versus True Lumbar Stiffness (The Finger-to-Floor Trap): The hamstring musculature originates from the ischial tuberosities. In patients with severe hamstring contracture, standing forward bend causes early tensioning of the posterior thigh, preventing the pelvis from rotating anteriorly over the femoral heads. The patient is unable to reach within 15 to 20 cm of the floor, creating a false-positive impression of lumbar spine rigidity. Strategy to Eliminate Trap: Always perform the seated forward bend test. Flexing the knees to 90° completely slackens the hamstrings; if the patient achieves full, fluid spinal flexion while seated, the spine is flexible and the deficit is purely muscular.
• Hip Flexion Contracture (The Thomas Test Trap): A fixed flexion deformity of the hip (common in end-stage hip osteoarthritis) mechanically prevents the femur from achieving neutral extension. In the upright standing posture, the patient is forced to tilt the pelvis anteriorly to keep the leg vertical, generating an obligatory compensatory hyperlordosis of the lumbar spine. During backward extension testing, the patient demonstrates an apparently restricted lumbar extension arc because baseline lordosis is already exhausted at rest. Strategy to Eliminate Trap: Perform the Thomas test and evaluate hip extension reserve in the prone position.
• Pelvic Rotation and Coronal Obliquity Compensation: Patients with leg length discrepancies, pelvic obliquity from degenerative scoliosis, or adduction contractures of the hip exhibit asymmetric pelvic torsion during forward bending. If inclinometers or Schober skin markings are applied without correcting pelvic tilt, asymmetrical skin stretch and out-of-plane pelvic rotation skew sagittal measurements. Strategy to Eliminate Trap: Level the pelvis using calibrated foot blocks under the short extremity prior to measuring spinal excursion.
• Paraspinal Muscle Spasm and Antalgic Guarding: Acute disc herniation, annular fissure tear, or acute facet arthropathy triggers intense, involuntary reflex contraction of the erector spinae and multifidus muscles. This acute muscular splinting produces severe functional restriction, mimicking structural ankylosis on the Schober test and dual inclinometry. Strategy to Eliminate Trap: Evaluate the patient in the supported prone position to assess passive paraspinal muscle tone, inspect for acute antalgic lateral shift, and reassess mobility after symptoms stabilize.
• Severe Obesity and Landmark Obscuration: In individuals with high body mass index (BMI > 35 kg/m²), prominent subcutaneous adipose tissue obscures the PSIS dimples and the spinous processes. Inaccurate landmark identification shifts baseline cutaneous marks cephalad or lateral, creating measurement errors on tape testing. Strategy to Eliminate Trap: Use deep palpation against the iliac crest apices to triangulate Tuffier’s line, or rely on digital inclinometry placed over bony reference points.

8. Comparative Utility & Clinical Decision Algorithm

To optimize diagnostic accuracy and guide surgical triage, physical examination maneuvers must be integrated into a structured clinical sequence and combined into validated diagnostic clusters:

• Systematic Physical Examination Sequencing:
  1. Upright Static Inspection: Inspect global sagittal balance, plumb-line alignment (C7 plumb line relative to posterior S1), pelvic obliquity, and knee flexion crouch.
  2. Active Regional Mobility: Evaluate active cervical arcs, seated thoracic rotation, and standing lateral bending.
  3. Objective Sagittal Lumbar Excursion: Perform the Modified Schober Test and Dual Inclinometry (T12 vs S1).
  4. Spinopelvic & Sacroiliac Dynamics: Execute the Gillet/Stork test and the standing versus seated forward flexion decoupling maneuver.
  5. Seated Neurological Examination: Test deep tendon reflexes, motor strength, and perform the seated slump test for neural tension.
  6. Supine and Prone Musculoskeletal Evaluation: Assess passive hip range of motion (internal and external rotation at 90° flexion), perform the FABER and FADIR tests, measure the popliteal angle (90-90 hamstring test), and perform the Thomas test for hip flexion contracture.
• Diagnostic Clustering for High-Yield Stratification:
  – Axial Spondyloarthritis Diagnostic Cluster: Modified Schober < 4.0 cm + positive Gillet test + positive SIJ distraction/compression + chest expansion < 2.5 cm. When all four findings are present, the positive likelihood ratio (LR+) exceeds 18.0, confirming axial spondyloarthritis.
  – Stiff Spinopelvic Complex in THA Candidates: History of instrumented lumbosacral fusion (or rigid degenerative spine) + restricted seated pelvic tilt + absence of normal lumbar rounding seated + normal popliteal angle (<30°). This cluster achieves an LR+ of 14.5 for dynamic spinopelvic stiffness, mandating specialized imaging.
• Advanced Imaging and Surgical Triage Algorithm:
  – Paired Standing and Slump-Seated Lateral Biplanar Radiography (EOS): Mandatory in any patient presenting for primary or revision THA who exhibits clinical spinopelvic stiffness, prior spinal fusion, or severe degenerative scoliosis. Measures Pelvic Incidence (PI), standing Pelvic Tilt (PT), standing Sacral Slope (SS), seated SS, and dynamic change in Sacral Slope (ΔSS).
    • If ΔSS < 10° ("Stuck Standing", standing PT < 13°): Utilize patient-specific component positioning (elevating acetabular cup anteversion to 20° to 25°), deploy dual-mobility articulations or large-diameter heads (≥36 mm), and utilize robotic navigation to prevent seated posterior dislocation.
    • If ΔSS 20°, PI-LL > 15°): Spine surgery consultation for deformity realignment prior to THA if the spinal deformity is symptomatic. If THA is performed first, avoid excessive cup anteversion to prevent standing anterior dislocation.
  – Lumbar Spine MRI: Indicated if the patient exhibits dermatomal radiculopathy, neurogenic claudication, progressive neurological deficits, or severe paraspinal muscle fatty infiltration on inspection.
  – High-Resolution Pelvic CT with 3D Modeling: Indicated for complex acetabular bone loss, severe retroversion, or when robotic/navigated arthroplasty platforms require 3D surface mapping.

9. Evidence-Based Synthesis

Modern clinical decision-making is grounded in high-quality randomized controlled trials and prospective registry analyses, corroborated by seminal biomechanical and anatomical descriptions.

10. References

• Legaye J, Duval-Beaupère G, Marty C, et al. Pelvic incidence: a fundamental pelvic parameter for three-dimensional regulation of spinal sagittal curves. European Spine Journal. 1998. doi:10.1007/s005860050038 [Level IV: Seminal Anatomic & Biomechanical Study]
• Roussouly P, Gollogly S, Berthonnaud E, et al. Classification of the Normal Variation in the Sagittal Alignment of the Human Lumbar Spine and Pelvis in the Standing Position. Spine. 2005. doi:10.1097/01.brs.0000152379.54463.65 [Level IV: Observational Anatomic Cohort Study]
• Schwab FJ, Blondel B, Bess S, et al. Radiographical Spinopelvic Parameters and Disability in the Setting of Adult Spinal Deformity. Spine. 2013. doi:10.1097/BRS.0b013e318292b7b9 [Level II: Prospective Multicenter Observational Study]
• Stefl M, Lundergan W, Heckmann N, et al. Spinopelvic mobility and acetabular component position for total hip arthroplasty. The Bone & Joint Journal. 2017. doi:10.1302/0301-620X.99B1.BJJ-2016-0415.R1 [Level III: Comparative Kinematic & Radiographic Cohort Study]
• Heckmann N, McKnight B, Stefl M, et al. Late Dislocation Following Total Hip Arthroplasty: Spinopelvic Imbalance and the Consequences of Spinal Fusion. Journal of Bone and Joint Surgery. 2018. doi:10.2106/JBJS.18.00078 [Level III: Retrospective Case-Control Comparative Study]

11. Master Class Pro-Tip

Always decouple the lumbar spine from the hamstrings by comparing standing active forward flexion directly against seated forward flexion. When a patient demonstrates restricted fingertip-to-floor reach standing but achieves effortless, full-arc spinal rounding and brings the chest flush to the thighs while seated with knees flexed at 90°, structural lumbar spine stiffness is definitively excluded—the restriction is driven entirely by hamstring contracture tethering the ischial tuberosities. Conversely, persistent flattening of the lumbar lordosis and an inability to flex during the seated test confirms true structural axial ankylosis, mandating paired standing and slump-seated lateral spinopelvic imaging prior to any hip or spine intervention.

Master Class Clinical Pearl: Precision Diagnostics in Spine and Pelvis Range of Motion