Fryette's Laws of Spinal Motion

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Fryette's Laws is a set of three laws pertaining to skeletal anatomy named after Harrison Fryette, D.O. The laws are defined as a set of guiding principles used by practitioners of osteopathic medicine to discriminate between dysfunctions in the axial skeleton. The first two laws solely apply to the lumbar and thoracic spinal regions, but the third applies to the entire vertebral column [1]


The first two laws were developed by Dr. Fryette in 1918, and the third was developed by C.R. Nelson, D.O in 1948.[2]

The 3 Laws

1. First Law / Neutral Mechanics 

  • When the spine is in neutral, sidebending to one side will be accompanied by horizontal rotation to the opposite side.
  • This law is observed in type I somatic dysfunction, where more than one vertebrae are out of alignment and cannot be returned to neutral by flexion or extension of the vertebrae.
  • The involved group of vertebrae demonstrates a coupled relationship between sidebending and rotation.
  • When the spine is neutral, side bending forces are applied to a group of typical vertebrae and the entire group will rotate toward the opposite side: the side of produced convexity. [3]
  • Extreme type I dysfunction is similar to scoliosis.

2. Second Law / Non – Neutral Mechanics [4]

  • When the spine is in a flexed or extended position (non-neutral), sidebending to one side will be accompanied by rotation to the same side.
  • Non-Neutral mechanics occur in the lumbar spine when it is forward bent.
  • In backward bending, the lumbar spine demonstrates neutral coupling.
  • In the thoracic spine, there is capability for both neutral and non-neutral coupling.
  • The type of coupling occurs to be a function of where you are in the thoracic curve, above or below the apex and whether you introduce side bending or rotation first.
  • In general, if side bending is introduced first, rotation will occur to the opposite side. If rotation is introduced first, side bending couples to the same side
  • This law is observed in type IIsomatic dysfunction, where only one vertebrae is out of place and becomes much worse on flexion or extension.
  • There will be rotation and sidebending in the same direction when this dysfunction is present.

3. Third Law

When motion is introduced in one plane it will modify (reduce) motion in the other two planes.The third principle sums up the other two laws by stating dysfunction in one plane will negatively affect all other planes of motion. [4]


  1. "Fryette's Laws - definition of Fryette's Laws in the Medical dictionary - by the Free Online Medical Dictionary, Thesaurus and Encyclopedia". Retrieved 2012-08-24.
  2. Savarese, Robert G.; Copabianco, John D.; Cox, James J. (2009). OMT review. pp. 3–5. ISBN 978-0967009018.
  3. Nelson, K and Glonek, T. Somatic Dysfunction in Osteopathic Family Medicine. Philadelphia: Lippincott Williams & Wilkins. p. 455
  4. 4.0 4.1 Philip E. Greenman; Principles of Manual medicine; lippincott Williams and Wilkins; 3 rd edn; pg:53 – 65