A frequently asked question in Myoskeletal Alignment seminars is how to differentiate sacroiliac from piriformis syndrome pain (Fig. 1).
Indeed, these structures are often involved in a symbiotic relationship. Length/strength piriformis imbalance strongly influences movement of the sacrum between the two hip bones and clinically, we know both can cause sciatic-like symptoms… a condition which affects nearly 40 percent of adults at some point during their lifetime.1
But, unlike SI joint dysfunction, piriformis pain is a “functional entrapment syndrome” resulting from a positional abnormality in which the sciatic nerve becomes compressed between piriformis and either the sacrospinous ligament and/or, the bony sciatic notch. The burning question is… why are some clients symptomatic and others not?
Is there a genetic predisposition or could a torsioned pelvic bowl possibly be contributing to this painful dysfunction?
In my early Rolfing days, I blamed piriformis syndrome on almost all non-low back sciatic pain symptoms because it was so easy to visualize muscle pushing on nerve. But through dissection studies, it became clear that even in athletic overuse cases, it takes more than a vigorous rubbing to damage the sciatic’s enveloping dura mater (Greek for tough mother).
Much like lumbar intervertebral disc herniations, the sciatic nerve must be squashed against something to trigger intraneural edema and accompanying neurological symptoms such as pain, numbness, tingling and weakness.
It is estimated that 40% of non-discogenic sciatica results from SI dysfunction and piriformis syndrome. 2 Of the six groups of hip and thigh muscles attaching to the pelvis, the piriformis suffers the greatest stress when it comes to binding down (stabilizing) the SI joint. Therefore, a torsioned pelvis due to foot pronation, a valgus knee, etc. can drag piriformis into an altered position in the sciatic notch causing sciatic nerve entrapment between muscle and bone (Fig. 2)
Bilateral hip and leg pain may indicate a ‘double-crush’ syndrome where lower quadrant muscle asymmetry displaces one SI joint and entraps the sciatic under piriformis on the contralateral side (Fig. 3).
Bottom Line: Even in the presence of a positive Pace, Freiberg or Beatty test, piriformis syndrome should never be treated as an isolated event.
A successful therapeutic approach begins with a full spinal and pelvic evaluation including functional spring tests, muscle length/strength comparisons, hip abduction firing order exams and, in extreme cases, an orthopedic referral may be necessary. I’ve found the new MRI neurography scan to be very helpful in weeding-out questionable piriformis, thoracic outlet and carpal tunnel syndrome cases.
Once positive identification of sciatic entrapment between the piriformis and bone (or sacrospinous ligament) has been verified, hip external rotator releases such as those shown in Figures 4 and 5, should help relieve neural compression allowing the dural membrane and capillary beds to heal.
Sacroiliac and Iliosacral Influences
Although there are 14 different dysfunctions possible within the pelvic girdle (some say more), iliosacral upslips and backward sacral torsions are at the top of my list as pain generators that mimic lumbar radiculopathies and piriformis syndrome. The most common of the sciatic-like SI joint dysfunctions is termed a right-on-left backward sacral torsion.
These people present with a short right leg, no spring at right sacral base or inferior lateral angle and have a convex left functional scoliosis. Typically caused by a forward bending and twisting incident, sciatic pain shoots into the buttocks and down the leg as the sacrum gets stuck rotated right and side-bent left between the two innominates (Fig. 6). Prolonged ligament and joint capsule stress caused by this torsion can sympathetically spasm the piriformis muscle causing contracture, fibrosis and a ‘double-crush’ sciatic episode. Though a torsional SI joint fixation may have been the original culprit initiating the sciatic assault, soon the fibrotic piriformis tightens its grip on the sciatic nerve crushing it against the sacrospinous ligament or bony sciatic notch. The end result of this double-crush disorder is inflammation, neural breakdown and interruption of the axoplasmatic flow of vital nutrients to the surrounding nerves.
Figure 7 demonstrates a simple, but effective technique for correcting this commonly misassessed SI joint problem.
The second most common pelvic pain-generator I see in clinic is an iliosacral upslip.
How many times have you heard a client say, “I just stepped off a curb (or missed a step on the ladder) and when I landed on one foot, a sharp pain shot into my hip?”
As the person’s body weight travels through the femur and acetabulum, the SI joint ligaments are overstretched allowing the ilium to move superior to the sacrum on that side.
We see this dysfunction more in women primarily because of fewer stabilizing bony grooves between the ilium and sacrum.
Although this injury does not mimic sciatic leg pain, the ‘sheared’ hip remains very painful until a successful manual therapy correction is made.
Figure 8 is the first step in correcting the client’s upslipped left ilium.
1. McCrory P, Bell S. Nerve entrapment syndromes as a cause of pain in the hip, groin and buttock. Sports Medicine, 1999 Apr;27(4):261-74.
2. Retzlaff E, Berry AH, Haight AS, et al. “The Piriformis Muscle Syndrome.”Journal of the American Osteopathic Association;73:799-807.