Where is it?
Your Piriformis muscle is a small muscle located in your gluteal area. It is attached to the back side of the lower spine, runs under several of the gluteal muscles, and the other end attaches to the greater trochanter (the big lump of bone at the top of the femur - the upper leg bone). It also runs very close to parts of the sciatic nerve, so pain and irritation in the Piriformis muscle can often be lumped together with, mistaken for, or blamed for sciatic pain.
What does it do?
The Piriformis is mainly responsible for externally rotating the thigh and upper leg, and abducting the leg (moving the leg sideways away from the other leg and core). This allows the leg to also rotate the knee and lower leg to move easily to allow the body to step sideways, lift the leg, and step forward while twisting. It also helps stabilize the hip joint and give support for the other muscles that flex, extend, and move the legs.
What makes them hurt?
It can be very easy to irritate the Piriformis muscle. Standing for very long periods of time like in people who stand at a stove or cash register all day, as well as sitting for long periods of time such as long commuters or those who sit while traveling or at a desk all day can irritate the Piriformis muscle and cause it to spasm. This also causes tightness throughout the hips and the low back. Unfortunately, since the Piriformis runs so close to the sciatic nerve, if the Piriformis gets tight, it can aggravate the sciatic, causing pain to radiate down the legs and up into the low back.
How can massage help?
Massage can target the gluteal muscles to loosen up the tight muscles in the hips. It takes a little work to get through the many gluteal muscles to reach the Piriformis since it is buried under many of them. But massage including work on various pressure points along the length of the Piriformis muscles can get it to relax and subsequently release tension and tightness in the low back and hips/gluteals.
What can I do besides massage to help them?
Doing any of the multiple variations of what is known as the "Figure 4 stretch" (in which one ankle is placed over the opposite knee, and the torso bends forward) will stretch out the Piriformis muscle. Ice and/or heat can also be used to settle down the pain in the muscle. Self-massage can also be done by sitting with a tennis ball under one butt cheek and wiggling for a little while when it hits a sore spot, until the sore spot releases a bit. If the pain is being caused by being on one's feet for long periods of time, an evaluation by an orthopedic or chiropractic professional may be used to make sure that posture and alignment are where they are supposed to be, or if support such as adjustments or orthopedic shoe inserts to keep the hips level and working equally may be needed.