If working a sweater in pattern, such as Mishke or Anna, I tend to work the sleeve in ribbing to keep the lines running vertically up the arm thereby slimming it. When you are working a sleeve in pattern, whether ribbing or some other pattern, you need to work the newly added stitches in the established pattern. This is difficult for some people to visualize.
Think of the underarm stitch or stitches as the trunk of a tree and the new sts grow off of it to join with the rest of the stitches. Here is the underside of Marta’s sleeve:
You have a center core of 2 knit stitches running all the way up but each stitch that is added on either side of that core must remain in pattern with the established pattern. This means that you’ll begin every round with k1, then make sure you continue with the established pattern to the last st, and no matter what, k the last st. As the sleeve grows you can see sometimes you will have 6 knits in a row, sometimes you will be in perfect pattern.
You may, as with Anna, have only one core knit running up the sleeve with increases on either side. The reason for this core running up the sleeve is to mimic a seam, thus keeping the sleeve increases neat-looking.