Danny, you can get stiff legs, soar legs, twitching legs from stress. Even RLS (Restless Leg Syndrome). I would see a doc to rule out other things, but trust me, I've been there and I suffer from Post Traumatic Stress. I was sure I had every illness out there until I began to understand the disorder.
I agree that it could very well be from stress, after all when you're stressed you tend to tighten up all of your muscles.
I do agree however that you should see a Doctor also, like Andrea said it could be RLS or ever arthritis...you don't have to be old to get arthritis believe me I know.
I was Dx'd with it at 25.