Emily kumpattk in Mesa Grande dictionary and in another example by Cuevas, though here sounds like emily kumputt, similar to meputtk (mepuuttk) "is short".
Literally, "his stub leg" or "his leg is a stub one", from emily "his leg" and kumpattk "which is short/broken off(?)", either from pattk (paattk) "is broken off" or from meputtk (mepuuttk) "is short".
Mesa Grande dictionary translates as if a verb: "has a peg leg (lit. short leg)", though it appears rather like a noun phrase.