Fig. 1 — The WAD ladder: grades 0 through IV, with the progression markers on grades I–III.
The mechanism: acceleration, then deceleration
In a rear-end collision the struck vehicle is shoved forward. The occupant's torso accelerates with the seat back, but the head — heavy, and attached only by the neck — lags for a fraction of a second. The neck is dragged into extension, then whips into flexion as the head catches up and overshoots. That sequence is cervical acceleration-deceleration, and the injury pattern it produces is what clinicians call whiplash.
Vehicle damage is a poor predictor of the injury: the energy that deforms bumpers is absorbed by the vehicle, while the energy that accelerates the occupant is what loads the neck. A low-speed collision with little visible damage can still produce a neck injury.
The Quebec Task Force grades
In 1995 the Quebec Task Force on Whiplash-Associated Disorders published a classification that remains the standard reference. It grades the clinical picture, not the collision:
- WAD 0 — no complaint about the neck, no physical signs.
- WAD I — neck pain, stiffness, or tenderness only; no physical signs.
- WAD II — neck complaint plus musculoskeletal signs: decreased range of motion, point tenderness.
- WAD III — neck complaint plus neurological signs: decreased or absent deep tendon reflexes, weakness, sensory deficits.
- WAD IV — neck complaint plus fracture or dislocation.
The grade is a clinical finding recorded in the medical record — it is one of the pieces of documentation the evidence file is built from.
Symptom onset: usually soon, sometimes late
The Task Force monograph noted that symptoms frequently appear within the first 24 hours after the collision — but delayed onset is common, with pain and stiffness sometimes emerging days later as inflammation builds. The late appearance of symptoms is not evidence that the injury is minor; it is how soft-tissue injuries declare themselves. The underestimation file covers that pattern in detail.
When to be evaluated: new or worsening neck pain, pain radiating into an arm, numbness, tingling, or weakness after a collision belong in a clinical evaluation. This desk does not triage — it documents the structure of the injury.
What whiplash means for the record
Because the WAD grade is assigned from the physical exam, the timing and content of the first evaluation matter. A grade recorded on day one reflects the day-one picture; symptoms that develop later can change the picture. The imaging file explains why the X-ray taken at the first visit rarely tells the whole story.