Stand and Deliver
"Do you know where your piriformis is?" Over the years I've gotten a variety of responses to this question: sometimes a blank stare, sometimes a laugh. Once in a blue moon, someone correctly points to the back of the hip.
If the location of the piriformis is a mystery to most yoga students, its action and its function in yoga poses are even more mysterious. Most students have no idea of the important work it performs. Unfortunately, the piriformis is best known for the problems it causes, including sciatica. But this obscure muscle is crucial in stabilizing the pelvis and knees.
Before we examine the action of the piriformis, let's clarify its whereabouts. It's located deep in the buttock, underneath the better-known gluteus maximus. The piriformis is part of a group of six muscles called the deep external hip rotators. These six muscles all originate at various locations on the back of the pelvis and cross the back of the hip to insert on the greater trochanter, a protuberance on the outer upper femur (thighbone) about six to eight inches below your waist. The position of the rotators, reaching from the back of the pelvis to the outer thigh, gives them excellent leverage to externally rotate the hips—in other words, to turn the legs outward.
Perhaps you've made the acquaintance of your rotators during a massage, when deep work on the back of a buttock brought your awareness to tight and tender muscles. That tenderness, which can range from minor soreness to sharp pain, may be due to overworked, strained, or chronically tight rotators. In such cases, massage, gentle stretching, and a reconditioning exercise program will help solve the problem. Poses that can help stretch a chronically tight piriformis include preparations for Eka Pada Rajakapotasana (One-Legged Pigeon Pose), the leg position of Gomukhasana (Cow Face Pose), and Ardha Matsyendrasana (Half Lord of the Fishes Pose).
However, the piriformis and its brother rotators sometimes get blamed for problems they didn't cause. The buttock is a common area for referred pain from lower back problems, including arthritis, disc injuries, and sacroiliac problems. So it's very important that any persistent hip pain be thoroughly evaluated by your health-care providers before you decide on a course of treatment.
While the piriformis and the other deep hip rotators are best known for the problems they create when they're tight, they do need to be strong to perform important functions in yoga poses. They help to stabilize the pelvis and knees when you bear weight on the legs, especially in standing poses. To experience this, stand with your legs wide, preparing for Virabhadrasana II (Warrior Pose II). Turn your right foot out 90 degrees and your left foot slightly in. Notice that even though the right foot is turned out, there is a tendency for the knee to turn in.
This internal rotation of the femur is due to the pull of the internal rotators of the hip, including the adductors (a large muscle group of the inner thigh) and the medial hamstrings on the back of the inner thigh. If the foot and shin rotate out while the femur rotates relatively in, the knee twists, putting a potentially damaging strain on its ligaments. A contraction of the external rotators is needed to bring the knee into alignment with the foot to protect the integrity of the knee joint.