bandy leg vs impairment

bandy leg and impairment both are nouns.

Word	Noun	Adjective	Verb	Adverb
bandy leg	Yes	No	No	No
impairment	Yes	No	No	No

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

bandy leg: a leg bowed outward at the knee (or below the knee)
impairment: the condition of being unable to perform as a consequence of physical or mental unfitness

Other hypernyms of bandy leg include leg, disability, disablement, handicap.

bandy leg (noun)	impairment (noun)
a leg bowed outward at the knee (or below the knee)	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