When you work in continental, do you use your left index finger elevated a bit to tension the yarn? If so, try this trick. As you make each stitch and prepare to go to the next one, give the yarn a tiny tug with your left index finger to snug it up against the needle. It doesn't have to be tight, just snugged up and not hanging loose. If you make it a habit to do this with every stitch you make, you will soon see your knitting straighten out and become more even. Don't forget to do this for both knit and purl stitches.
Using the conventional purl stitch sometimes results in a looser tension when purling than when knitting. This tiny tug technique should help with both kinds of stitch. If that doesn't work out for you after a bit of practice, you may want to try knitting continental combo style.
The different manner of wrapping for the purl stitch makes it easier to get an even tension. With practice, your knitting will be very even--it's just the nature of knitting combo style. (This wrap style can be used for both right hand throw and left hand continental. Just wrap the purl stitch from the bottom up between the two needles instead of from the top down. This will result in the stitch mount switching from the front of the needle to the rear, but it is consistent and causes no trouble whatsoever once you learn to watch for it and knit accordingly.
I am halfway through knitting an Irish Aran sweater, and have used continental combo for the entire thing. There is only one part of the pattern where I reverse the mount of two stitches in order to avoid twisting. The rest, including all the cables, honeycomb, etc. are no problem at all, and the overall result is quite even. Of course, because of having multiple cable twists on every other row, there are a few stitches that are not exactly perfectly tensioned, but they are most definitely more even than when I attempt to do this style of knitting using the "regular" purl wrap direction.
Just remember, always work with the leading leg of the stitch. That is, if the stitch was off the needle and laid out flat, the leg on the right would be the leading leg. In knitting in this style, it may occasionally be on the front of the needle, but is more commonly on the back. It is the same exact motion that you get when your instructions say "Knit through back loop." Except that you do it all the time for knit stitches.
There are several videos demonstrating this method on YouTube. Check them out. It's really easier to see what I'm talking about than to understand my written instructions.
You may have someone tell you that you cannot knit certain stitches using this method. To that I say, in the immortal words of Nero Wolfe, Phooey! If I can knit an entire Aran sweater using this style of knitting, I hope that puts to rest that silly idea. Both side panels of this sweater are in seed stitch, and of course the bottom of the sweater and the cuffs of the sleeves are in ribbing. All work perfectly well, and quite evenly tensioned in combo knitting. The same is true for circular knitting. No problem, just an occasional adjustment of stitch mount if you want to do matching pairs of left leaning or right leaning decreases.
One advantage of this with arthritis (I have arthritis in my left index finger, and my right thumb, so I know whereof I speak. Combo is the way to go. You can use either continental or right hand carry and it makes no difference in the final product. If your fingers get tired using one method, switch to the other.
Honestly, when I am working in Aran, I generally use right hand carry (throwing) for the cable twist rows, and continental left hand carry for the back side rows which have no twists. Of course, it can be done either way, this is just a habit I have gotten into as it helps to rest my fingers every other row.
(The Teddy Bear in my avitar picture is an Aran which I finshed about 3 weeks ago. It, too, is knit entirely in combo style. As you can see by the various patterns, this style of knitting can be used literally for all kinds of knitting. It is the style I teach beginners from day one. The left hand continental or right hand throw is their option, but all students are taught in combo style.)
