Maybe this is an amazing discovery of a big argument, maybe not. Here I write down what I just found – Before 3000 years, when the 商周 persons said the words related bones, they pronounced “k” in these words. These are some examples(the pronunciations are from Baxter, 2014 ):
骨 – *【k】ˤut
肩 – *【k】ˤen
膝 – *stsi【k】
臂 – *pe【k】s
足 – *tso【k】s
甲(finger nail) – *【k】ˤrap