Fryette's principles and how to name a spinal dysfunction

5 min read. Updated October 9, 2026.

Fryette's principles describe how rotation and sidebending travel together in the spine, and they are how OMM names a spinal dysfunction. Principle I (Type I): in neutral, sidebending and rotation go to opposite sides, across a group of segments. Principle II (Type II): in flexion or extension, they go to the same side, at a single segment. Principle III: moving a segment in one plane changes how much it can move in the other two. Principles I and II describe the thoracic and lumbar spine; Principle III applies to the whole spine, neck included.

The three principles

	Type I	Type II
Position	Neutral (no strong flexion or extension preference)	Flexed or extended
Sidebending and rotation	Opposite sides	Same side
Usual scope	A group of segments	One segment
Rotation goes toward	The convexity of the curve	The side of sidebending
Example	T5-T9 N SL RR	T6 F RR SR

Principle III: introducing motion in one plane modifies motion in the others. Flex a segment and its sidebending and rotation change. This is why diagnosis compares neutral, flexion and extension, and why treatment positions combine planes.

How a dysfunction is named

A dysfunction is named for its position of ease: the directions the segment moves into freely, not the directions it is restricted.
It describes the upper vertebra relative to the one below.
Rotation is named for where the front of the vertebral body faces. Rotated right means the body turns right, so the right transverse process moves back.
Notation: F, E or N (flexed, extended, neutral), plus R with the rotation side and S with the sidebending side. T6 F RR SR is T6 flexed, rotated right and sidebent right. Type II segments are usually written rotation first (F RR SR) and Type I groups sidebending first (N SL RR); the order does not change the meaning.

Reading the vertebra

The posterior transverse process is the rotation side. Right TP back means rotated right.
In the simplified model the spinous process points opposite to the body's rotation: rotated right, spinous process to the left.
Translation tests sidebending. Pushing a segment to the right (right translation) creates left sidebending. If right translation is restricted, left sidebending is restricted, and the segment prefers to sidebend right.
Always test motion as well as position. A congenitally asymmetric vertebra or a bent spinous process can look rotated without being dysfunctional.

Tripositional diagnosis

Find the posterior transverse process in neutral. That gives the rotation.
Flex the patient and recheck. Then extend and recheck.
If the TPs become level in flexion and worse in extension, the segment is flexed. If they level in extension and worsen in flexion, it is extended. Name it Type II: sidebending goes with rotation.
If the asymmetry stays the same in all three positions across several segments, it is a neutral group. Name it Type I: sidebending goes opposite rotation.

What you find	Diagnosis
Right TP of T6 posterior; level in flexion, worse in extension	T6 F RR SR
Right TP of T6 posterior; level in extension, worse in flexion	T6 E RR SR
Left TP of L2 posterior; level in flexion, worse in extension	L2 F RL SL
Right TPs posterior from T5 to T9; no change with flexion or extension	T5-T9 N SL RR

A posterior TP that only shows up in extension does not prove flexion on its own; read the whole comparison.

Practice naming

Name it

Left transverse process of T4 posterior in neutral
The T4 asymmetry disappears in flexion
In extension, the T4 asymmetry gets worse

F, E, N: flexed, extended, neutral. RR: rotated right. SL: sidebent left. Named for the position of ease.

Groups and curves

A group dysfunction is a curve. A curve that is convex to the right is sidebent left and rotated right: N SL RR. A curve convex to the left is N SR RL.

Group treatment usually targets the apex of the curve.
A Type II segment can sit inside a group curve, but it does not have to be at every apex.

Treatment follows from the name

Once you have the name, both treatment directions are fixed:

Direct techniques take the segment to its barrier: the opposite of every part of the name. For T6 F RR SR, that is extension, left rotation and left sidebending.
Indirect techniques take it into ease: flexion, right rotation and right sidebending for the same segment.

The thoracic rule of threes

The thoracic spinous processes slope down, so a spinous process does not sit at the level of its own transverse processes. This palpation rule estimates where it is:

Vertebrae	Spinous process tip sits at
T1-T3	Its own transverse processes
T4-T6	Halfway between its own and the next vertebra's transverse processes
T7-T9	The next vertebra's transverse processes
T10	Like T7-T9: one level down
T11	Like T4-T6: half a level down
T12	Like T1-T3: its own level

Individual anatomy varies; this is a surface estimate.

Region	Superior facets face	Memory hook
Cervical	Backward, upward and medially	BUM
Thoracic	Backward, upward and laterally	BUL
Lumbar	Backward and medially	BM

The inferior facets face the opposite way. Orientation changes gradually between levels, and the lumbosacral facets are more coronal than the upper lumbar ones. Thoracic rotation is relatively free; extension is limited by the rib cage and posterior elements.

Where the rules change

Exams emphasize the transition zones: OA, C7-T1, T12-L1 and L5-S1. Mechanics change at each one, and dysfunction often collects there. C2-C7 couple sidebending and rotation to the same side regardless of position, and OA and AA have their own patterns.

Frequently asked

What is the difference between Type I and Type II somatic dysfunction?

Type I is neutral, involves a group of segments, and has sidebending and rotation to opposite sides (for example T5-T9 N SL RR). Type II is flexed or extended, usually involves one segment, and has sidebending and rotation to the same side (for example T6 F RR SR).

Does Fryette's first principle apply to the cervical spine?

No. Principles I and II describe the thoracic and lumbar spine; only Principle III applies to the neck as well. C2-C7 rotate and sidebend to the same side, OA rotates and sidebends to opposite sides, and AA mainly rotates.

How do you know if a segment is flexed or extended?

Compare the posterior transverse process in neutral, flexion and extension. If the asymmetry goes away in flexion, the segment is flexed; if it goes away in extension, it is extended. If it does not change across a group of segments, it is neutral.

Which way does the spinous process point when a vertebra rotates right?

To the left. The vertebral body turns right, the right transverse process moves back, and the spinous process swings left.

What is the rule of threes?

A palpation estimate for thoracic spinous processes: T1-T3 sit at their own transverse process level, T4-T6 halfway down to the next level, and T7-T9 a full level down. T10 behaves like T7-T9, T11 like T4-T6 and T12 like T1-T3.