PM is a key to the lower extremity. Association of the PM with sciatic and other nerves in the gluteal area make PMS a very frequent pathological condition. As a matter of fact every abnormality on the lower extremity starting from the thigh down to the foot (from active trigger points in hamstring muscles to Plantar Fasciitis) may be directly connected to PMS.
This article consists of three parts. Part I will review the anatomy and physiology of PM, Part II will present the evaluation of the patient with tension in PM and Sciatica and Part III will show the entire MEDICAL MASSAGE PROTOCOL in cases of PMS.
The PM originates inside the pelvis on the anterior surfaces of the sacrum and the sacro-iliac joint, exits the pelvis via the greater sciatic foramen, and inserts into the greater trochanter (see Fig. 1).
a
b
The greater sciatic foramen is formed anteriorly and laterally by the ilium bone, medially by the sacrum, inferiorly by the sacrospinous ligament (see Fig 2).
Fig. 2. Greater sciatic foramen
When the PM leaves the pelvis, it divides the greater sciatic foramen on thesuprapiriformis recess and the infrapiriformis recess (see Fig. 1b).
In some individuals especially those who build up the PM in gym or during a professional sports career the PM may occupy the entire greater sciatic foramen to the degree of eliciting pressure on neurological and vascular structures located in this anatomical opening (Ripani, et al., 2006). The PM receives motor innervation from the S1-S2 spinal nerves.
The PM participates in the abduction and lateral rotation of the hip joint. The gluteal muscles, including the piriformis and quadratus lumborum muscles, are key players in our ability to walk upright. Every time we lift a foot to take a step, the opposite side quadratus lumborum muscle binds together the thoracic cage with the pelvis, and at the same time the entire gluteal group stabilizes the hip joint. With such simultaneous action, the opposite side of the body becomes a rigid structure which acquires enough stability and balance to resist the force of gravity while we are finishing the step and are on both feet again.
If we look at the anatomy of the gluteal muscles, it is noticeable that all of them originate from the outer surface of the pelvic bones and sacrum and insert into the greater trochanter (see Fig. 1a). Only the PM starts from the inside of the pelvis (see Fig. 1b) and uses the same area of insertion (i.e., greater trochanter).
Despite the fact that the PM shares similar action to the other gluteal muscles, it is the only biomechanical force which stabilizes the hip joint from the inside of the pelvis and balances the action of all the other gluteal muscles. This is what makes the action of the PM so unique.
In the difference with other gluteal muscles, the PM is able to participate in the lateral rotation and abduction in the hip joint while prime movement of other gluteal muscles is mostly the lateral rotation in the hip joint.
The PM has one more unique biomechanical characteristic. It is able to elicit direct pressure and rotation force on the sacro-iliac joint (Retzlaff, 1974). This fact greatly contributes to the tension in the SI joint and lower back pain {forms} as a result of Sacroiliitis.
The PM is an absolutely unique muscle in our body, because of its complex relation with many important nervous and vascular structures in the pelvis and gluteal area. The tension in the PM may affect following structures.
1. Sacral Plexus
As we discussed above, the inner third of PM is located inside the pelvis. In the place of origin (anterior surface of the sacrum and SI joint) the PM forms a cushion for the sacral plexus especially to S2-S3 spinal nerve roots (Russell et al., 2008). This plexus is the origin of many nerves (i.e., sciatic, gluteal inferior, cutaneous posterior, etc.) which innervate the pelvic inner organs, the gluteal area, and the lower extremities. Fig. 3 presents the anatomy of the sacral plexus and its relation to the PM borders which are emphasized by solid red lines.
Fig. 3. Sacral plexus and PM
Clinical importance: If the PM gets tense the sacral plexus doesn’t have soft support anymore and symptoms of irritation of the sacral plexus may develop. The patient will exhibit a great variety of the clinical signs and symptoms because the sacral plexus is the origin of the majority of peripheral nerves, which supply the pelvis and both lower extremities.
The clinical signs of the irritation of the sacral plexus by the PM is a unique combination of the lower back pain, peripheral symptoms in the lower extremity and variety of visceral symptoms (e.g. constipation, intense menstrual pains, erectile dysfunction, etc.).
2. Sciatic Nerve
PMS is the major cause of Sciatic Nerve Neuralgia (SNN). The sciatic nerve is composed of two nerves: the tibial nerve (the anterior portion of the L4-S3 spinal nerves) and the common peroneal nerve (the posterior portion of the L4-S2 spinal nerves).
The sciatic nerve has several variants in its position in regard to the PM. Beaton and Anson (1938) in their classical study examined 2250 cadavers and found that sciatic nerve has the following major pathways in regard to the PM.
1. In 85% of the population the sciatic nerve has the most common route when entire nerve exits the pelvis via the infrapiriformis recess, i.e. it is located below the PM (see Fig. 4 ‘a’).
2. In 10% of the population the tibial portion of the sciatic nerve passes below the PM while the common peroneal portion of the sciatic nerve penetrates the PM (see Fig. 4 ‘b’).
3. In 2-3% of the population the tibial portion of the sciatic nerve passes below the PM while the common peroneal portion of the sciatic nerve passes above the PM (see Fig. 4 ‘c’).
4. In 1% of the population both portions of the sciatic nerve penetrate the PM (see Fig. 4 ‘d’).
5. 1-2% of the population exhibit less frequently occurred pathways
Fig. 4. Sciatic nerve and PM
1 – common peroneal portion of the sciatic nerve
2 – tibial portion of the sciatic nerve
As you may see from Fig. 1 the common peroneal portion of the sciatic nerve is more frequently in trouble. This is why patients with PMS are more likely to develop sensory and motor abnormalities within the distribution of the common peroneal nerve (Lee and Tsai, 1974; Limansky, 1988). However, both portions or only the tibial nerve portion can be entrapped as well. For those patients, the clinical picture of Sciatic Nerve Neuralgia is much more intense and they struggle with constant flare ups during their entire life.
3. Gluteal Nerves and Arteries
The superior gluteal nerve and artery exit the pelvis via the suprapiriformis recess. The inferior gluteal nerve and artery exit the pelvis via the infrapiriformis recess. The superior gluteal nerve innervates gluteus medius, gluteus minimus and tensor fascia latae muscles.
The inferior gluteal nerve innervates the gluteus maximus muscle.
Clinical importance: irritation of the gluteal nerves is accompanied by the formation of the active trigger points, protective muscle tension and weakness in the gluteal muscles.
The clinical sign of the inferior gluteal nerve neuralgia is weakness or complete inability (in cases of complete palsy) to get up from the seated position.
The clinical sign of the superior gluteal nerve neuralgia is an unusual rolling gait. Every time one raises foot on the unaffected side to make a step the half of the pelvis on the affected side slightly goes downward instead of being on the same level. The rolling gait is especially visible if the examiner gets on one knee to bring his or her eyes to the level of the patient’s pelvis and asks the patient to walk slowly while observing the gait from the back and comparing both sides.
4. Pudental Nerve and Artery
The pudental nerve is a major source of innervation of the sexual organs in males and females. It innervates penis, scrotum, clitoris, labia as well as anal sphincter and urethral sphincter. Finally pudental nerve contributes to the innervation of the skin on the posterior thigh.
Clinical importance: irritation of the pudental nerve is a direct cause of sexual dysfunction in men and women (e.g., erectile dysfunction, dryness of vagina, pain during intercourse, etc.) and sensory abnormalities (e.g. tingling, numbness) on the posterior thigh.
The goal of Part I of this article is to illustrate the fact that PM is a critical player in the human body and any, even the slightest pathological changes in its function causes a rich neurological picture in the pelvis, gluteal area and in the lower extremities. In other words, the PMis a key to the pelvis and lower extremities and the practitioner’s ability to handle the tension in the PM greatly contributes to the overall success of the therapy of variety of somatic and visceral symptoms in the lower back, pelvis and lower extremities.
Part II of this article in the next issue of the Journal of Massage Science will cover evaluation of the client with tension in the PM and symptoms of Sciatica.
Lee C.S., Tsai T.L. The Relation of the Sciatic nerve to the Piriformis Muscle. J. Formosan Med Assoc., 73:75:75-80, 1974
Lymansky Y.P., Macheret E.L., Vaschenko E.A. The Neurological Symptoms of the Spodylosis. ‘Zdorovie’, Kiev, 1988
Retzlaff E.W., Berry A.H., Haight A.S., Parente P.A. The Piriformis Muscle Syndrome. JAOA, 73:799-807, 1974
Ripani M., Continenza M.A., Cacchio A., Barile A., Parisi A., De Paulis F.The Ischiatic Region: Normal and MRI Anatomy. J. Sports Med Phys Fitness, Sep, 46(3):468-475, 2006
Russell J.M., Kransdorf M.J., Bancroft L.W., Peterson J.J., Berquist T.H., Bridges M.D. Magnetic Resonance Imaging of the Sacral Plexus and Piriformis Muscles. Skeletal Radiology, Aug, 37(8):709-713, 2008
Category: Medical Massage