The knitted neck tie is more casual than its silk colleague. 

A knitted tie works very well with odd jackets.

The casual look is die to the coarser textures as a result of the knotting process.

Whilst the majority of knotted ties have a square cut finish, a diamond-cut end look (see the photo above) less plump. 

Knitted ties of a finer knit (like the one above) are less casual and more elegant, although less so than silk ties.