How to Do the 90/90 Stretch for Healthy, Mobile Hips

Tight hips? Welcome to the club. While there are lots of great hip mobility exercises and stretches out there, the 90/90 stretch is one of the best.

Also called the 90/90 hip switch, this drill can help with your hip mobility and, specifically, hip rotation. That's good, because your hips' ability to rotate is probably shrinking each year. In fact, in a February 2012 ​Orthopaedis & Traumatology Surgery & Research​ study, scientists found that every year we age, our hip mobility decreases by 0.32 degrees.

That might not seem like a lot, but over a decade, that's 32 degrees of motion — about a tenth of the way around a circle. And reduced range of motion in your hips has some big consequences — like low back pain and increased risk of injury to the knees, including anterior cruciate ligament (ACL) tears.

The 90/90 stretch increases mobility both in external rotation — when your foot twists toward the center of your body — and internal rotation, when your foot is twisted out to the side. Here's what you need to know to add this hip-mobilizing move to your routine.

• ​What is the 90/90 stretch?​ It's a seated mobility exercise that turns one hip in a position called "external rotation," while the other hip turns out in "internal rotation." It increases hip mobility, which can help reduce injury risk and pain.
• ​What does the "90/90" position mean?​ When in the full stretch, your knees will both form 90-degree angles.
• ​What muscles does it stretch?​ Hip flexion — the act of lifting your thigh up toward your torso or shifting it back toward your glutes — uses 11 different muscles in the hip. They're collectively called the hip flexors, and include the iliacus, psoas major and piriformis. This move targets these hip flexor muscles. It also stretches the glutes, the hip abductor muscles (which are located on the outside of the hip and help move the leg away from the middle of your body) and the hip adductor muscles, also called the inner thighs.
• ​Who can do this stretch?​ This is an advanced mobility exercise, especially in its basic form, but most anyone can do it in a way that feels good (even great!) to them. If you experience pain or pinching in your obliques, back, hips or knees, stop doing the move and try one of the below variations.

When your hip rotates your thigh so that your foot and calf come toward the midline of your body, it's called "external rotation." Lots of exercises and stretches, like a yoga pigeon pose, externally rotate the hip. The 90/90 stretch is unique in that it also rotates the hip internally; the back leg, where the thigh is turned away from the midline of the body, is rotated in this way.

In the ​Orthopaedis & Traumatology Surgery & Research​ study, scientists found that 47 percent of people had more external hip rotation than internal rotation. Only 13 percent of people had more internal rotation than external. So you may have the most room for improvement when it comes to internal rotation.

When athletes have less ability to internally rotate their hips, they're more likely to tear their anterior cruciate ligaments, or ACL, according to a September 2014 study in ​Knee Surgery, Sports Traumatology, Athroscopy​. ACL tears can sometimes happen when the knee collapses inward, a position called "valgus."

Because the 90/90 hip stretch increases your ability to internally rotate the hip, it could help reduce the risk of ACL injury.

The connection between tight hips and low back pain is well established. And studies have also found that increasing hip mobility can help reduce that pain. For example, during a 2015 study in ​The Journal of Back Musculoskeletal Rehabilitation​, people reduced their lower back pain with just six weeks of hip rotation stretching.

If your torso leans way over to one side, you're not stretching the hips evenly, or in the way the exercise is intended to work.

If you struggle with the 90/90 hip switch and have a hard time sitting up straight with your weight in both hips, place a block under one hand to bring your torso up to a vertical position — you'll feel your hips sink down as you do. You can also rest your front knee on a rolled blanket or mat.

If they're not, you may feel a twist and pinch in your knee. Keeping them at 90 will help focus the stress of the stretch in your hips — which is right where you want it.

When performing a yoga pigeon pose (in which the back leg is extended straight) some practitioners lean forward to deepen the stretch. But when doing the 90/90 for hip mobility, you should stay up tall: Leaning forward tilts your pelvis and takes some stretch out of the front hip.

To fully benefit from the stretch, you need to relax into it. That requires both deep, slow breathing ​and​ finding a comfortable position! Explore the position and variations to find the right fit for your body.

If your hips are especially tight, you'll probably want to start with one of these less-intense versions of the 90/90 stretch. Modifying will allow you to get into the stretch properly and safely. Work your way up to the OG when you're ready.