What is Normal? - Rating Tip of the Week

First we must know the working definition of 'normal' as outlined in the Guides (5th ed.,2):

'range or zone representing healthy functioning'

Impairment is present when this normal state is altered. The Guides offer the following discussion on 'Normal':

'When evaluating an individual, a physician has two options: consider the individual's healthy pre-injury or pre-illness state or condition of the unaffected side as 'normal' for the individual if this is known, or compare that individual to a normal value defined by population averages (5th ed., 2).'

The accepted population values as described above are those values listed in the Figures and Tables for each chapter.

The Guides explain how to calculate impairment when the contralateral upper extremity measurements are less than the normal values in the Figures and Tables. Chapter 16, The Upper Extremities, offers the following discussion:

'If a contralateral 'normal' joint has a less than average mobility, the impairment value(s) can serve as a baseline and are subtracted from the calculated impairment for the involved joint (5th ed., 453).'

It is appropriate to make adjustments for each component of the motion impairment rather than the added impairment values.

Example:

Shoulder Flexion on the injured right is 140 degrees resulting in 3% upper extremity impairment. Shoulder flexion on the uninjured left is 150 degrees resulting in 2% upper extremity impairment. The 3% is subtracted from the 2% to result in a true impairment for flexion of 1%.