When used at the beginning of a sentence, this word is a variety of the 'filler' word basically. Another direct replacement for technically is essentially. Maybe the speaker sees his or her own bad speech patterns and recycles these three words while speaking. Filler words add absolutely nothing to the sentence being spoken. Other filler words include like, just, and stuff and y'know, but they tend to be in the middle of or at the end of a sentence. Filler words are rarely used in writing and are part of acquired speech habits.
Technically, the knee bone is connected to the thigh bone.
Why not say... The knee bone is connected to the thigh bone.
Means basically. If some thing is complicated, or a smudge complex, it can relate back to the first bit. Just look at the example...
i drew a picture for my boyfriend, but I also decided to copy it and enter it into a contest; when i give to to him, i will say 'Technically, i made this for you' since that isn't the only reason I used it.