hip issue

I have noticed recently after riding my Gunnar that I've a bit of soreness deep inside my hip that has a bit of arthritis. This doesn't happen when mountain biking, but that is a quite different activity and a different riding position. Of course I also start/stop more frequently on the mountain bike.

Currently after a ride I do hip/quad/hamstring/calf stretches that take me about 10 minutes.

It isn't pain, just a bit of soreness, and I am unaware of it until I get off the bike. I probably need to get back to Pilates, but they canceled the one class I could actually make...

I only know of one hip stretch, and while there are many others, are there any stretches best for targeting the hip joint? This isn't muscular soreness, I've learned what THAT feels like ;) I wouldn't be surprised to learn that this is perhaps fit or cleat related.