Why is everybody talking about the piriformis and where the heck is it?
For such a small muscle, the piriformis seems to get a lot of attention. It does play an important role as a hip stabilizer and an external rotator, but it doesn’t act alone. There are actually three other external rotators and stabilizers of the hip that play an equally significant role: the superior and inferior gemellii, and the obturator internus.
So why does this one little muscle get a whole syndrome named after it? Actually many doctors, including us at ARB, wonder the same thing. The answer seems to revolve around the piriformis’ proximity to another extremely important structure, the sciatic nerve. The piriformis muscle and sciatic nerve are very close neighbors that even demonstrate various positioning throughout the population: for the majority of the population, the sciatic nerve lies directly beneath the lower edge of the piriformis; others demonstrate a split sciatic nerve lying above and below the piriformis; and a small group actually have their sciatic nerves bisect the muscle itself. That being said, in all actuality, all four deep external rotators, as well as the gluteus medius and maximus muscles, are positioned close enough to the sciatic nerve to cause irritation. Perhaps a more appropriate name might be “sciatic nerve entrapment syndrome”?
Traditionally, piriformis syndrome is used to describe a condition in which tension within only the piriformis muscle produces entrapment and irritation of sciatic nerve. This entrapment can be caused by numerous soft tissue factors including an excess of scar tissue surrounding the nerve or a muscle imbalance. Since the sciatic nerve is such a large nerve, it produces a variety of symptoms when entrapped. Typically, a patient complains of a deep ache in the hip. Occasionally there is pain and/or paresthesia (abnormal tingling or sensation) traveling down the back of her/his thigh and can even travel into the calf and foot. Symptoms are often exacerbated when the patient perform squats or stands from a seated position. Frequently, patients notice symptoms more with sitting and during car rides. Repetitive activities such as walking, running, and cycling can become quite uncomfortable.
While the positioning of the anatomy plays an important role, there are many avoidable risk factors that contribute to developing this syndrome. As the main hip external rotators are actually the gluteus maximus and gluteus medius, weakness and imbalance within these muscles impede on proper function of the deep hip rotators, thus, causing tension. Wearing improper footwear, running on banked surfaces, and sitting all day (especially if you have a wallet in your back pocket) are also common causes. Pregnancy, and the resulting relaxation of the pelvic bowl ligaments, is a potential cause, as the deep rotators must now pick up the slack for the ligaments.
As one can see, while small, these muscles can cause big problems. Thankfully, the most effective form of treatment is a conservative one that can be handled by most soft tissue specialists. While “sciatic nerve entrapment syndrome” is, both literally and figuratively, a pain in the butt, when treated correctly, it is not an injury that has to stop you from doing the activities that you love.
1. Michaud, T. Conservative Management of Hamstring Strains, Part 1. Dynamic Chiropractic 2012; 11:24, 383-385