Hi Tabbied, welcome to the forum.
My first sign of the meno was painful hips - I was hobbling at one point and it really messed with my yoga practice (no more half lotus for me!). And as for horse riding... I used to get cramp in one hip joint when I tried to dismount! I find the pain/stiffness comes and goes - probably with the fluctuating hormones.
Vit D helps (the spray from Holland & Barrett is very good).
More exercise is better than less, strangely enough. I've started weight training at the gym using free weights, and building up the muscles has helped with all my joints. It's hard work but worth it.
Make sure your diet is filled with lots of fresh veg, and don't skimp on the fat. Good fats like olive oil, sunflower oil, fish oil and nuts is what we need at our age. Think of it as oiling the machine!