knee / nee are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
knee: (noun) hinge joint in the human leg connecting the tibia and fibula with the femur and protected in front by the patella. (noun) the part of a trouser leg that provides the cloth covering for the knee.
nee: (adjective) (meaning literally `born') used to indicate the maiden or family name of a married woman.
knee: n·IY
nee: n·IY
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)