The piriformis is a small, relatively short, and little-known muscle buried deep within the muscle tissue in your hips.
In each hip, it runs from the back of your pelvis to the top of your femur. Because of its unique positioning, the piriformis muscle helps rotate your leg outward when your hip is extended, but rotates your leg inward and into abduction when your hip is flexed.
When running, the piriformis is most active during the “stance” phase, where your foot is planted on the ground. Here, it acts as an external rotator of the leg, but it is neither the primary nor the most powerful muscle which acts in that role.
Despite its seemingly insignificant function in the muscular support of your body while running, it plays a central role in a complicated and frustrating injury known as piriformis syndrome.
Epidemiology: Causes, what makes it worse, what’s going on
The reason this unassuming muscle can be so problematic is likely because it is positioned immediately adjacent to the sciatic nerve, a very thick nerve which runs from the base of your spine along your glute muscles and down the back of your legs, providing the nerve signals that allow all of the muscles on the back side of your lower body to fire when needed.
When the piriformis muscle is irritated, the sciatic nerve can get irritated too. In around fifteen percent of people, the sciatic nerve actually passes throughthe piriformis, which, according to some researchers, leaves these individuals more susceptible to piriformis syndrome.
Classically, piriformis syndrome feels like an aching soreness or tightness in your butt, between the back of your pelvis (the sacrum, specifically) and the top of your femur.
Pain, tightness, tingling, weakness, or numbness can also radiate into your lower back and down the back side of your leg, through your hamstrings and calves.
Buttock pain and tightness with prolonged sitting is also a common occurrence with piriformis syndrome.
When you run, you will probably feel pain in your butt throughout the stance phase of your stride; the pain might get worse when you run fast, go up and down hills, or go around tight turns.
Piriformis syndrome is related to sciatica, a painful irritation which also involves pain, tightness, weakness, and a numb or tingling sensation than courses down from your lower back into your butt, hamstring, and calves or even feet. How the piriformis muscle and the sciatic nerve relate to piriformissyndrome and sciatica-like pain is something that even doctors and researchers can’t quite agree on.
Their interactions are complicated, as there can be many causes of buttock pain and sciatic nerve pain. The mere existence of a “piriformis syndrome” has even been questioned, but the most current research and review papers accept that piriformis syndrome represents a real phenomenon that is responsible for buttock and lower leg pain.
Distinguishing piriformis pain from similar symptoms
Regardless, it is very important to distinguish piriformis syndrome from other problems that can cause similar symptoms in the buttock and leg. A herniated disc in your lower back, for example, can put pressure on the sciatic nerve, causing the same type of pain that radiates down the back side of your leg, as can spinal stenosis (a narrowing of the canal where your spinal cord passes through) and a host of other pelvic and lower back issues.
Though there are no universally agreed-upon criteria for piriformis syndrome, a comprehensive review paper published in 2010 by Kevork Hopayian and other doctors at the University of East Anglia in the UK provides useful criteria. In their study, they defined piriformis syndrome as “sciatica [i.e. musculoskeletal pain in the leg] arising from pressure on the sciatic nerve trunk or its branches by the PM [piriformis muscle] or disorders involving the muscle.”
This definition is useful as it encompasses both sciatica-like pain radiating down through the hamstrings that is likely the result of pressure on the sciatic nerve, as well as localized pain and soreness in the piriformis muscle itself. Hopayian et al. also outlined the four most common findings in patients with piriformis syndrome among the 55 studies they examined:
Pain in the buttock/piriformis region
Tenderness at a specific spot in the pelvis between the sacrum and the top of the femur—the area the piriformis muscle runs through.
Worsening of buttock and sciatica-like pain with prolonged sitting
Aggravation or alteration of the pain when the hip and leg are positioned to put tension on the piriformis muscle
While these symptoms are definitely evident in people with piriformis syndrome, it’s unclear how common they are in people with non-piriformis-related sciatica, so its diagnostic usefulness is somewhat limited.Fortunately though, other conditions that can cause similar symptoms can be identified by objective medical tests like an MRI or a CT scan—these can check for herniated discs or other low back and pelvis issues. If these tests come back clean, piriformis syndrome can be considered as a cause.
Specific tests for piriformis syndrome
There are also a few specific tests for piriformis syndrome that have been highlighted in scientific studies.
In the straight-leg raise test, pain shooting down the back of your leg when your leg is raised straight (typically by a partner) while you lie on your back is indicative of irritation of the sciatic nerve, though it is not specific to piriformis syndrome.
Another test can be performed while sitting: attempting to push your knees out against resistance (provided by a partner or rope) can cause pain in some people with piriformis syndrome.
Finally, two maneuvers which put a stretch on the piriformis muscle can also be used to test for piriformis pain. Having a partner rotate your hip and leg inwards while you lie on your back with your knees straight can produce pain, as can lying on your unaffected side and rotating the painful side across your body with your knee bent.
The straight-leg raise test can cause sciatica-like pain if you have piriformis syndrome, but might also indicate the presence of low back problems
One test which can produce piriformis-specific pain is a supine internal leg rotation, assisted by either by a partner or a rope, as illustrated here.
Stretching the piriformis in this position can elicit pain (red area) if you have piriformis syndrome
Pain might also occur if you attempt to abduct your hips from a sitting position against resistance provided by a partner or a rope.
Though these piriformis-specific tests can help confirm the presence of piriformis syndrome, they are not accurate enough to rule it out. Hopayian et al.’s review study found no one technique to be reliable or accurate enough to endorse; rather, they cited the more general symptom of aggravation or modulation of piriformis pain when you stretch or tension the piriformis muscle.
You might also be able to feel a thickening in the piriformis muscle itself, deep within your glutes, but this is also not enough by itself to definitively diagnose piriformis syndrome.
Research-backed treatment options
As you might have been able to guess from the ambiguity of the symptoms and diagnosis criteria, piriformis syndrome is not a heavily-studied injury, in runners or even in the population at large. Even case studies of piriformis syndrome in athletes are extremely difficult to come by, so our approach to treatments will have to rely more heavily on a theoretical approach versus one backed by high-quality clinical trials.
Most treatments for piriformis syndrome that are recommended in scientific literature are focused on addressing the painful or irritated piriformis muscle that’s (presumably) the cause of the buttock and leg pain. This largely consists of stretching and strengthening exercises.
Case studies and case series articles from the scientific literature recommend using several different stretches for the piriformis. Based on what we know about the anatomy of the piriformis muscle, we can come up with ways to stretch it—if, when the hip is in flexion, the piriformis acts as an internal rotator and abductor, we can stretch it by putting our hip into externalrotation and adducting it.
Stretches for the piriformis
This is exactly what is accomplished in the stretches recommended by Douglas Keskula and Michael Tamburello in a 1992 article on treatments for piriformis syndrome.
Supine piriformis stretch with a crossover (moving left knee towards right shoulder)
Supine piriformis stretch without a crossover (moving heel towards right shoulder)
Supine piriformis stretch assisted by opposite leg (moving right knee towards right shoulder)
Keskula and Tamburello recommend starting with three sets of five to ten repetitions of each stretch two or three times per day.
Though Keskula and Tamburello only vaguely describe how long each stretch should be held (progressing “as tolerated” by the athlete), another paper by Pamela Barton at the University of Western Ontario in Canada recommends beginning with holding stretches for five seconds and gradually progressing over time to 60 seconds. You should be gentle with the stretches, not overly aggressive—this may put too much stress on the already-irritated piriformis.
Strengthening exercises for the piriformis
Strengthening exercises are also recommended in several different scientific papers. As the piriformis works as an abductor and rotator of the hip, strengthening both the piriformis itself and the other hip muscles that surround it is a primary goal of treatment.
A 2010 case report by Jason Tonley and a group of fellow physical therapists describes in detail a strengthening protocol used to successfully treat piriformis syndrome in a 30-year-old recreational athlete who displayed many of the classic signs of poor hip muscle coordination: inward knee rotation during single-leg squats and poor hip abduction and external rotation strength.
To address this, the authors prescribed a 14-week, three step program for hip muscle rehabilitation.
The first phase consisted only of glute bridges and clamshell leg lifts, both using a theraband for resistance.
After four weeks, the patient progressed to weight bearing exercises: standing mini-squats (with a theraband), “monster walk” side steps (also with a band), a “sit-to-stand” exercise, and single-leg mini-squats.
Following four weeks of the second phase, the patient progressed to lunges, deep squats, and even plyometric-style hops and landings (with the intent to prepare him to return to basketball and tennis, his principle sports).
In all phases of rehab, the patient progressed over time to three sets of fifteen repeats of each exercise.
A similar program designed for runners is illustrated below. Start gradually, but build up over time to three sets of 15 repeats of each exercise.
author: J. Davis