bow legs vs impairment

bow legs and impairment both are nouns.

Word	Noun	Adjective	Verb	Adverb
bow legs	Yes	No	No	No
impairment	Yes	No	No	No

As nouns, impairment is a hypernym of bow legs; that is, impairment is a word with a broader meaning than bow legs:

bow legs: outward curvature of the legs
impairment: the condition of being unable to perform as a consequence of physical or mental unfitness

Other hypernyms of bow legs include disability, disablement, handicap.

bow legs (noun)	impairment (noun)
outward curvature of the legs	damage that results in a reduction of strength or quality
	the act of making something futile and useless (as by routine)
	the occurrence of a change for the worse
	the condition of being unable to perform as a consequence of physical or mental unfitness
	a symptom of reduced quality or strength