Sometimes, (like now), I just ache all the way down the back of both legs, down my thighs and down my calves.
Ache probably may not be the description for the feeling.
I have had PSA for 20 years.
I beleive it is something to do with PSA or at least something inflammatory, 2 weeks ago it was so back I took a large dose of methylprednisolone and then weaned myself off, and it took away the pain for a week or so.
That's what I was thinking too. The fact that it went away when you took a round of prednisone means that it was inflammatory in nature. I'm wondering if you might benefit from physical therapy.
Physical therapy is specific structured exercises, stretching, etc, done under the guidance of a physical therapist. It is targeted at a specific problem, and you would need a prescription for it from your doctor. For example, a few years ago my shoulders had become quite weak and painful. So I went to physical therapy, to stretch and strengthen using specific exercises, that got more challenging as I got stronger. If I had tried at home, I wouldn't have balanced this for my needs, and likely would have given up quickly. I did work on my ankles last year, and on my hips (and knees) most recently. Good thing I like my physical therapist!
I walk every day as well. But when my hip got too painful for me to walk, I needed to do some work. My hips were unstable in some directions, and too tight in others. Much better now. Not perfect, there's still some mild damage, but much better.