If you sit at a desk all day, like me, you probably have tight hips. Imagine if you were holding a box in your arms with your elbows at 90 degree angles -- your arms would be flexed. Now, think about holding that box for 8 hours. Your biceps would be massively sore and your triceps wouldn't have gotten work all day.
Your hips are similar. When you sit all day, your hips are in that flexed position and your glutes are under-worked. I'm not suggesting that you go out and quit your day job, but I am suggesting that you should consider incorporating some hip openers into your exercise routine. You should also incorporate some glute strength work to help them to catch up and stay strong.
Come into a high lunge position and then slowly lower your back knee down to the ground. You want to press your hips forward on this one so that you feel the stretch in the hip of your back leg.
From the low lunge position, lift your back foot up and take it into your hand, if possible. From here, you can slowly pull it in towards your body and then release it back out, alternating.
Let your back foot return to the ground and then start to wiggle your front foot inward, lowering your knee to the ground slowly. You want to try to make your front leg perpendicular to your back leg. If you're super flexible, your hip might touch the ground, if not, it can hover.
Pull your back knee in and come into a sitting position. You want the leg that was previously in pigeon on top and the leg that was in the back on bottom. Your shins should be about parallel.
Slowly walk your hands forward to get a deeper stretch.
Remain here for a moment and then start back at low lunge with the other leg!