European Spine Journal

, Volume 22, Issue 5, pp 1059–1065 | Cite as

The effect of simulated knee flexion on sagittal spinal alignment: novel interpretation of spinopelvic alignment

  • Chong Suh Lee
  • Se Jun Park
  • Sung Soo Chung
  • Keun Ho Lee
Original Article



Many studies regarding spinal sagittal alignment were focused mainly on above-hip structures, not considering the knee joint. Knee–spine syndrome was proposed earlier, but the mechanism of this phenomenon has not been revealed. The aim of the study was to demonstrate how spinopelvic alignment and sagittal balance change in response to simulated knee flexion in normal non-diseased population.


Thirty young male were enrolled in the study cohort. Two motion-controlled knee braces were used to simulate knee flexion of 0°, 15°, and 30° settings. Whole spine and lower extremity lateral radiographs were taken at each knee setting of 0°, 15°, and 30° flexion. Spinal and pelvic parameters were measured, including two angular parameters, femoropelvic angle (FPA) and femoral tilt angle (FTA).


The following equation can be made; PT (pelvic tilt) = FPA + FTA. The mean values of FPA and lumbar lordosis decreased significantly at 15° and 30° knee settings compared to the parameters at the 0° knee setting, while the mean values of pelvic tilt and sacral slope rarely changed. Results also showed FTA was not correlated with PT, but strongly correlated with FPA (R = −0.83, p < 0.01).


The knee flexion resulted in decrease of lumbar lordosis without a significant change of pelvic posture in non-diseased population group.


Simulation Knee flexion Femoral tilt angle Femoropelvic angle Lumbar lordosis Pelvic posture 



The current study was supported by Central Research Fund (nonprofit academic fund) from our institute. This study was conducted under approval of IRB.

Conflict of interest



  1. 1.
    Bernhardt M, Bridwell KH (1989) Segmental analysis of the sagittal plane alignment of the normal thoracic and lumbar spines and thoracolumbar junction. Spine (Phila Pa 1976) 14:717–721CrossRefGoogle Scholar
  2. 2.
    Berthonnaud E, Dimnet J, Roussouly P, Labelle H (2005) Analysis of the sagittal balance of the spine and pelvis using shape and orientation parameters. J Spinal Disord Tech 18:40–47PubMedCrossRefGoogle Scholar
  3. 3.
    Cohen J (1988) Statistical power analysis for the behavioural sciences, 2nd edn. Lawrence Erlbaum Associates, HillsdaleGoogle Scholar
  4. 4.
    Gelb DE, Lenke LG, Bridwell KH, Blanke K, McEnery KW (1995) An analysis of sagittal spinal alignment in 100 asymptomatic middle and older aged volunteers. Spine (Phila Pa 1976) 20:1351–1358Google Scholar
  5. 5.
    Glassman SD, Bridwell K, Dimar JR, Horton W, Berven S, Schwab F (2005) The impact of positive sagittal balance in adult spinal deformity. Spine (Phila Pa 1976) 30:2024–2029CrossRefGoogle Scholar
  6. 6.
    Jackson RP, Hales C (2000) Congruent spinopelvic alignment on standing lateral radiographs of adult volunteers. Spine (Phila Pa 1976) 25:2808–2815CrossRefGoogle Scholar
  7. 7.
    Lafage V, Schwab F, Patel A, Hawkinson N, Farcy JP (2009) Pelvic tilt and truncal inclination: two key radiographic parameters in the setting of adults with spinal deformity. Spine (Phila Pa 1976) 34:E599–E606CrossRefGoogle Scholar
  8. 8.
    Lazennec JY, Ramare S, Arafati N, Laudet CG, Gorin M, Roger B, Hansen S, Saillant G, Maurs L, Trabelsi R (2000) Sagittal alignment in lumbosacral fusion: relations between radiological parameters and pain. Eur Spine J 9:47–55PubMedCrossRefGoogle Scholar
  9. 9.
    Mangione P, Senegas J (1997) Sagittal balance of the spine. Rev Chir Orthop Reparatrice Appar Mot 83:22–32PubMedGoogle Scholar
  10. 10.
    Min K, Hahn F, Leonardi M (2007) Lumbar spinal osteotomy for kyphosis in ankylosing spondylitis: the significance of the whole body kyphosis angle. J Spinal Disord Tech 20:149–153PubMedCrossRefGoogle Scholar
  11. 11.
    Murata Y, Takahashi K, Yamagata M, Hanaoka E, Moriya H (2003) The knee–spine syndrome. Association between lumbar lordosis and extension of the knee. J Bone Joint Surg Br 85:95–99PubMedCrossRefGoogle Scholar
  12. 12.
    Roussouly P, Nnadi C (2010) Sagittal plane deformity: an overview of interpretation and management. Eur Spine J 19:1824–1836PubMedCrossRefGoogle Scholar
  13. 13.
    Roussouly P, Pinheiro-Franco JL (2011) Biomechanical analysis of the spino-pelvic organization and adaptation in pathology. Eur Spine J 20(Suppl 5):609–618PubMedCrossRefGoogle Scholar
  14. 14.
    Schwab F, Lafage V, Boyce R, Skalli W, Farcy JP (2006) Gravity line analysis in adult volunteers: age-related correlation with spinal parameters, pelvic parameters, and foot position. Spine (Phila Pa 1976) 31:E959–E967CrossRefGoogle Scholar
  15. 15.
    Schwab F, Lafage V, Patel A, Farcy JP (2009) Sagittal plane considerations and the pelvis in the adult patient. Spine (Phila Pa 1976) 34:1828–1833CrossRefGoogle Scholar
  16. 16.
    Schwab F, Patel A, Ungar B, Farcy JP, Lafage V (2010) Adult spinal deformity-postoperative standing imbalance: how much can you tolerate? An overview of key parameters in assessing alignment and planning corrective surgery. Spine (Phila Pa 1976) 35:2224–2231CrossRefGoogle Scholar
  17. 17.
    Vaz G, Roussouly P, Berthonnaud E, Dimnet J (2002) Sagittal morphology and equilibrium of pelvis and spine. Eur Spine J 11:80–87PubMedCrossRefGoogle Scholar
  18. 18.
    Yoshimoto H, Sato S, Masuda T, Kanno T, Shundo M, Hyakumachi T, Yanagibashi Y (2005) Spinopelvic alignment in patients with osteoarthrosis of the hip: a radiographic comparison to patients with low back pain. Spine (Phila Pa 1976) 30:1650–1657CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Chong Suh Lee
    • 1
  • Se Jun Park
    • 1
  • Sung Soo Chung
    • 1
  • Keun Ho Lee
    • 1
  1. 1.Department of Orthopedic Surgery, Spine Center, Samsung Medical CenterSungkyunkwan University School of MedicineSeoulKorea

Personalised recommendations