There are 409 4-letter words containing K in the ENABLE dictionary — 10% of all 3,903 words at this length. At 5 points, K is worth more than most tiles without being awkward enough to hold back for — it is generally better placed than saved.
The K falls in the fourth position more often than any other, in 186 of them. 11 of them use the letter more than once — kaka, kaki, keck, keek among them, which is the case worth checking twice when a game has told you a letter is present but not how many times.
If you know more than one letter, this page stops being the fast way to find it. Enter what you have in the unscrambler — the Contains, Starts with and Ends with filters combine, and setting both length fields to 4 narrows this list to the handful your letters actually allow.
Where the K sits
K in the first position (121)
kaas kabs kadi kaes kafs kagu kaif kail kain kaka kaki kale kame kami kana kane kaon kapa kaph karn kart kata kats kava kayo kays kbar keas keck keef keek keel keen keep keet kefs kegs keir kelp kemp keno kens kent kepi keps kept kerb kerf kern keto keys khaf khan khat khet khis kibe kick kids kief kier kifs kike kill kiln kilo kilt kina kind kine king kink kino kins kips kirk kirn kirs kiss kist kite kith kits kiva kiwi knap knar knee knew knit knob knop knot know knur koan koas kobo kobs koel kohl kola kolo konk kook koph kops kore kors koss koto kris kudo kudu kues kuru kvas kyak kyar kyat kyte