The degrees you find listed with the motions of the various joints in this text refer to what is considered “normal” ROM.
“Normal” for the intents and purposes of this text means what most people are capable of doing without showing any signs of weakness, strain, discomfort or pain.
Different Levels of Flexibility
As people have different base lines in regard to their flexibility, bilateral comparison can often provide you with valuable information in addition to the “normal” ROM.
If possible conduct moves simultaneously on both sides.
In most people the dominant side is a bit stronger, right handed people are likely to be stronger on their right.
If there is a big discrepancy between the two sides, consider nerve damage and the client might have to be referred out, in particular if there is atrophy of muscles.