No offense but this is a sophomoric take. I'd be willing to bet that more native English words have irregular spelling than norman/Latin/other imports. The same thing happened in French too. Often orthographic changes lags pronouciation changes. The reason many English words have irregular spellig is because English has been a written language for a long time. That is why you have words like Knight, Knee, Enough, Eight, Cough, etc which are all native words. My understanding is the k in kn words used to be prounouced.
Knee is the same in German as it is in English. However, the Germans pronounce the K, e.g., "Kah-nee."
The word for "Knight" in German is "Ritter" if I am not mistaken? Though, I have no idea where the word Knight comes from. (Which I intend to look up after posting this).