We usually say elbow is 팔꿈치! I think in 태권도 they said striking elbow is called 팔꿉치기 instead of 팔꿈치 치기.(팔꿉 is like adjective of 팔꿈치. But it's not adjective. I just said to understand easier that explanation.) So, that homepage wrote 팔꿉.. In my opinion.. So if you wanna say elbow, it's 팔꿈치 And if you wanna say striking elbow, you can say 팔꿉치기