OMM

Fryette's Laws & Spinal Mechanics

OMM

Fryette's Laws & Spinal Mechanics

Type I (neutral, group) vs Type II (non-neutral, single segment).

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◆Fryette's First Law (Type I — Neutral)

•In NEUTRAL position, side-bending and rotation occur to OPPOSITE sides
•Involves a GROUP of vertebrae (≥3 segments)
•Compensatory, usually chronic, asymmetric posture
•Example: T5–T8 NSRRL (neutral, side-bent R, rotated L)

◆Fryette's Second Law (Type II — Non-neutral)

•In FLEXION or EXTENSION, side-bending and rotation occur to the SAME side
•Involves a SINGLE segment
•Often acute, traumatic, painful
•Example: T4 FRSR (flexed, rotated R, side-bent R)
•Type II dysfunctions get priority for treatment

◆Fryette's Third Law

•Motion in one plane modifies (limits) motion in the other planes
•Practical: if a segment is held in flexion, side-bending and rotation will be reduced

◆Applies to thoracic & lumbar ONLY

•Cervicals follow different rules (especially C0–C2)
•C2–C7 typically: side-bending and rotation are coupled to the SAME side (Type II-like)
•OA (C0–C1): side-bending and rotation OPPOSITE
•AA (C1–C2): essentially pure rotation (no side-bending coupling)

Type I vs Type II

Feature	Type I (Neutral)	Type II (Non-neutral)
Position	Neutral	Flexed or extended
Coupling	Side-bending opposite rotation	Side-bending SAME side rotation
Segments	Group (≥3)	Single segment
Onset	Chronic, compensatory	Acute, often traumatic
Treatment priority	Lower	HIGHER
Example	T5–T8 NSRRL	T4 FRSR or T4 ERSL

High-yield pearls

◆Mnemonic: Type I — 'opposite' (neutral); Type II — 'same' (flexed/extended)
◆Treat Type II FIRST when both are present
◆Cervical spine doesn't follow Fryette's laws (C2–C7 = same-side coupling regardless of position)
◆OA reversed: side-bend and rotation are OPPOSITE

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