When we hear "hip openers" in a yoga context, most of us think of poses that stretch our outer hips — and specifically that primary outer rotator, the piriformis — like pigeon pose, lizard pose, and related. But recently, I was working with a private client who has very tight hips and she showed me what she'd been doing to open them, which was pigeon pose. However, because it was the only stretch she was doing, the surrounding muscles were staying tight, and she wasn't making substantive progress. So I helped her put together a more integrated plan (yes, pigeon pose, but we added quite a few other stretches) that I'll share here with you.
To stretch the hamstrings:
When the hamstring muscles tighten along the back of the thighs, they pull the back of the pelvis down, tilting it backwards. This distortion moves the hip sockets forward and up, and prevents effective opening of the outer hips. To open the back of your legs, try forward folds like a standing forward bend (uttanasana). Be sure to center the stretch in the middle back of your thighs. If you're on the less flexible side of the spectrum, working with bent knees will help you move the stretch from your back into your legs.
To stretch the back muscles:
Speaking of the hamstrings, I've noticed that their opening is often blocked due to tight muscles in the back. Broaden those with these twists and side stretches such as revolved chair pose (parivrtta utkatasana) and revolved triangle (parivrtta trikonasana ). Also incorporate side openers like standing crescent (indudalasana) and gate pose (parighasana).
To stretch the IT bands:
The iliotibial band is a ligament, not a muscle, but it interacts and connects with muscles of the outer leg. When it's tight or inflamed, it can prevent the kneecap from lining up in a healthy way and further tighten the outer hips. Check out my blog on IT bands here.
To stretch the hip flexors:
The hip flexor muscles contract and shorten whenever we sit, or ride a bike, or even walk up a flight of stairs, and they are opened by extension of the hips. When they stay tight, they can pull the tops of the femurs (thigh bones) forward in the hips, preventing the thigh bone from rotating effectively in the hip socket. I see this over and over again in clients, and notice that it tends to further tighten the outer hips.
I suggest a restorative form of bridge poses (setu bandha sarvangasana) with a block placed under the low back for added support, as well as what I consider the holy grail of hip openers — reclined hero's pose (supta virasana). I wrote a lot more in-depth info about opening these pesky, tight muscles here.
To stretch the quadriceps:
Tight quads behave similarly to tight hip flexors, preventing the femoral head (top of the thigh bone) from moving congruently in the hip socket. Without congruency, it's nearly impossible to open the outer hips effectively. Stretch these muscles in half frog pose (ardha bhekasana) or reclined hero's pose (supta virasana).
In short, you've got to take a trip around the hips to open effectively! As you move through that journey, spend extra time with the muscles that are tightest for you.