I gather that part of the tacit-knowledge movement is to talk about knowledge that cannot be put into words. The example of how to move a muscle is extremely instructive: There is no sequence of words that will allow a person to examine and select the correct bundles of nerves for moving a muscle, and instead a person simply must learn to do it somehow. Even then, if somebody does something like isolating grouped muscle movements, they might be able to explain in words how to fine-tune control over some muscles.