I think you'll need to post some more info on how you do it and perhaps some source code on where you are stuck/that doesn't work.

In the meanwhile. A simple google on "2D Skeletal animation" gave enough hits with samples that might help you fix your problem. For example: http://www.catalinzima.com/2011/06/2d-skeletal-animations/

I've never used 2D skeletal animation myself, so I'm not sure if it is possible in topdown, or maybe just not in the general way. Instead of moving an arm, for example, from left to right (mostly move the X component and some of the Y component) you would want to move up and down, but not that much so you can create the illusion of a swaying arm (so moving only the Y component up and down). I'm not sure if this will work, but that's a general thought that pops up in my head if I would face this problem.

As for spritesheets. Those are valid and maybe a better solution depending on what you want to do. If you just want to have a walking motion in 4 ways, you can get away with a couple of frames to animate movement and perhaps a couple of attack frames. The nice thing about 2D skeletal animation is that you don't have the draw every frame yourself (as in, really drawing, nothing to do with rendering) while with a spritesheet, you'll need draw every animation frame, so you can understand that with a lot of different animations, you'll end up with big spritesheets and an artist doing a lot of work.

So, check how much you want to do and what will be the most viable option, if your artist doesn't matter drawing all the frames of every animation frame, go for it. I don't think I'm able to help you any further than that though. Perhaps someone with more experience in 2D skeletal animation can help you out here.