Human Movement Science & Functional Anatomy of the:
Piriformis
by Brent Brookbush MS, PES, CES, CSCS, ACSM H/FS
Piriformis Image - Gray's Anatomy 20th Edition via Bartleby.com, found on wikimedia.com
Anatomy:
- Origin: Anterior surface of the sacrum between (and lateral to) the first through the fourth sacral foramina, margin of the grater sciatic foramen and pelvic surface of the sacrotuberous ligament (11).
- Insertion: Superior border of the greater trochanter of the femur.
- The pirformis lies deep to the gluteus maximus . The insertion of the piriformis lies on the superior aspect of the greater trochanter between the insertions of the gluteus minimus and gluteus medius , the lateral aspect of this muscle lies superficial to the sciatic nerve and the muscle becomes progressively deeper as it traverses through the greater sciatic notch of the ilium, and invests in the anterior surface of the sacrotuberous ligament and anterior sacrum. This muscle is bordered inferiorly by the gemellus superior superficially, and the coccygeus on the anterior surface of the sacrum.
- This muscle may be palpated by finding the spinous process of S2 with your thumb (the first prominent spinous process on the sacrum), and finding the greater trochanter with your index finger. The nearly horizontal line between these two points should outline the piriformis. Sinking your fingers deep to the gluteus maximus and running your fingers gently up and down should result in the relatively thin band like muscle being "strummed" underneath your fingers. Be careful not to compress the sensitive sciatic nerve (12).
- The pirformis lies deep to the gluteus maximus . The insertion of the piriformis lies on the superior aspect of the greater trochanter between the insertions of the gluteus minimus and gluteus medius , the lateral aspect of this muscle lies superficial to the sciatic nerve and the muscle becomes progressively deeper as it traverses through the greater sciatic notch of the ilium, and invests in the anterior surface of the sacrotuberous ligament and anterior sacrum. This muscle is bordered inferiorly by the gemellus superior superficially, and the coccygeus on the anterior surface of the sacrum.
- Nerve: Nerve to the Piriformis via the Sacral Plexus arising from the S1 & S2 nerve roots (sometimes L5)
Note the close proximity of the piriformis to the coccygeus -http://www.physio-pedia.com/images/5/59/Pelvic_floor.png
Actions:
- Hip:
- Primary external rotator and horizontal abductor of the hip
- Frontal plane abduction, possibly a weak hip extensor (3, 11).
- Special Considerations: Internal rotator of the hip when the hip is flexed beyond 90 - 100°
- Sacrum:
- Extension, anterior rotation, and some elevation to the same side.
Note the origin outlined in red on the bottom half of the anterior sacrum:
Anterior Sacrum - Gray's Anatomy - 20th Edition - http://bartleby.com/107/24.html#i95
Integrated Function:
- Stabilization: Hip and sacroiliac joint
- Eccentrically Decelerates: Hip internal rotation, adduction and potentially flexion
- Synergists:
- The piriformis is one of the "Deep Rotators of the Hip", along with the obturator externus, obturator internus, gemellus superior, and gemellus inferior. These muscles are responsible for external rotation when the hip is in neutral and horizontal abduction when the hip is flexed to 90º.
- The piriformis may play a role in a synergy that may become over-active due to dysfunction and inhibition of the gluteus maximus and the gluteus medius - most apparent in dysfunction resulting in "Knees Bow Out" during an "Overhead Squat Assessment ." The piriformis becomes synergistically dominant along with the biceps femoris and the posterior head of the adductor magnus during hip extension (eccentric flexion). These muscles may imply a fascial relationship as they all have origins on the sacrotuberous ligament. Further, this may implicate the piriformis as part of the Deep Longitudinal Subsystem (DLS) adding the erector spinae to this synergy. For more on this relationship and specific techniques for addressing this issue click on the article “Posterior Hip and Thigh Flexibility ."
- The piriformis is one of only four muscles that may directly impact sacral motion and stabilization of the sacroiliac joint. This synergy includes the transverse abdominis, gluteus maximus and coccygeus. For more on sacral motion you can check out - "Sacroiliac Joint Motion and Predictive Model of Dysfunction "
Piriformis on Anterior Sacral Surface - Primal Pictures - http://www.denverbackpainspecialists.com/wp-content/uploads/2012/05/Sacral-Anterior-Ligaments-and-piriformis.
Arthrokinematics:
- SI Joint: Anterior Rotation, extension (counter nutation), and elevation
- It is my hypothesis that this may place the sacral articular surface and iliac articular surface in a position of maximum congruence. Over-activity may result in arthrokinematic dyskinesis and excessive joint stiffness. For more information see Sacroiliac Motion and Predictive Model of Dysfunction .
- Hip: May contribute to a posterior rotatory force and anterior glide of the femoral head along with an adaptively shortened posterior capsule.
Piriformis - Cadaver dissection with gluteus maximus reflected: Note the piriformis and sciatic nerve. RVU Anatomy - http://www.rvuanatomy.com/
Fascial Integration:
- Origin on the sacrotuberous ligament - may infer a relationship between the piriformis, adductor magnus and biceps femoris . The sacrotuberous ligament may act to transmit force and proprioceptive information, stimulating a reflexive increase in tone and integrated function when any one of these muscles is stimulated. As mentioned above this may explain the over-activity seen in all of these muscles when inhibition of the gluteus maximus results in excessive external rotation during extension ("Knees Bow Out) during functional movement patterns. Further, this may implicate the piriformis as a "member" of the Deep Longitudinal Subsystem (DLS) , and add the erector spinae to this fascial synergy via the deep layers of the thoracolumbar fascia that run nearly continuous with the sacral fascia and sacrotuberous ligament.
- The piriformis invests into the periosteum at the superior aspect of the greater trochanter, lying between the gluteus minimus and gluteus medius attachments. Although the borders of these attachments are fairly distinct, it may be worth further study to determine the effect increased tension or pressure on the greater trochanter may have on muscle activity and recruitment patterns.
Subsystems:
- The piriformis is not generally thought of as having a role in Core Subsystem recruitment, but may play a role in the Deep Longitudinal Subsystem (DLS) via the sacrotuberous ligament, discussed above in "Fascial Integration"
Behavior in Postural Dysfunction:
This muscle has a tendency toward over-activity, but may be short or long depending on the compensation pattern (posture) adopted. We find altered activity and length in lower leg dysfunction and lumbo pelvic hip complex dysfunction and sacroiliac joint dysfunction. For more information on these predictive models of dysfunction click on the links below:
- Lower Leg Dysfunction (LLD)
- Lumbo Pelvic Hip Complex Dysfunction (LPHCD)
- Sacroiliac Joint Dysfunction (SIJD)
If Lower Leg Dysfunction (LLD) presents with "Knees Bow In" during an Overhead Squat Assessment , than the piriformis is implicated as long and over-active. However, if LLD presents with "Knees Bow Out" the muscles of the posterior hip and thigh (click on the hyperlink for flexibility techniques) including the pirifomis, biceps femoris , and posterior head of the adductor magnus are short and overactive.
As above, if Lumbo Pelvic Hip Complex Dysfunction (LPHCD) presents with "Knees Bow In" than the piriformis may be long and over-active, but generally it is not a priority in treatment. If LPHCD presents with "Knees Bow Out" than the piriformis is implicated as short and overactive and may be release and stretched.
In Sacroiliac Joint Dysfunction (SIJD) the compensation pattern adopted and side of dysfunction must be carefully assessed. As a counternutator of the sacrum the piriformis is often short and overactive on the side of SIJD, but the piriformis may also become short and overactive on the side opposite the shift. Commonly, the side of dysfunction is opposite the side of the shift, but careful assessment of the SIJ should be used to confirm findings.
**The Piriformis may Contribute to the Following Pathologies:
**
- Knee Pain
- Patellar tendonitis (Jumper's Knee)
- Lateral knee pain (Runner's Knee)
- Generalized knee pain
- Sacroiliac Joint Pain and Dysfunction
- SI Joint Pain
- Hip Pain
- Impingement Syndrome
- Greater Trochanteric bursitis
- Generalized hip pain
- Lumbar spine pain
- Excessive lordosis
- Inadequate lordosis
- Functional scoliosis
- Piriformis Syndrome
- Generally presents as sciatica, but is thought to be caused by the sciatic nerve bisecting or piercing the piriformis rather than coursing underneath it.
- Sciatica
- Note: the relationship between the sciatic nerve and piriformis in the picture below. A long and overactive piriformis may mechanically compress the sciatic nerve leading to irritation.
- Pelvic Floor Dysfunction
Piriformis - Gray's Anatomy 20th Edition - located on barleby.com
Signs of Altered Length/Tension and Tone:
- Overhead Squat:
- Assymetrical Weight Shift - Short/Overactive side Opposite Shift
- Knees Bow Out - Short/Overactive
- Posterior Pelvic Tilt - Short/Overactive
- Anterior Pelvic Tilt - Long/Overactive
- Knees Bow In - Long/Overactive
- Single Leg Squat:
- Hip Hike - Short/Overactive
- Hip Drop (Positive Trendelenburg) - Long/Overactive
- Goniometry (Indication of restriction and over-activity):
- Hip Internal Rotation < 45° w/ muscular end feel (at 90º of hip flexion)
- Note: A hard or capsular end feel may be partially caused by piriformis tightness, but is often confounded by tightness and over-activity in other structures resulting in anterior glide syndrome or anterior capsule impingement (example: TFL, Psoas, Adductors, Posterior Capsule)
- Hip External Rotation < 45° (at 90º of hip flexion) w/ muscular end feel (confirmed with similar findings in prone)
- Hip Internal Rotation < 45° w/ muscular end feel (at 90º of hip flexion)
- Special Tests for Sacroiliac Joint:
- SI Joint Dyskinesis
- Palpation of SI Joint
- Visual Observation of SI Joint motion
- FABERE or Patrick Test
- Functional Leg Length
- Palpation of Piriformis
- Tenderness (indication of over-activity)
- Trigger points (indication of over-activity and chronic postural dysfunction)
Trigger Point Map for Piriformis:
www.triggerpoints.net
The "Long and Overactive" Conundrum:
Very few muscles behave in a way that leads to an increase in length and an increase in activity. Generally, an increase in length leads to under-activity, latent activation and weakness. Although muscles that are long are often activated/strengthened, muscles that are over-active often become synergistically dominant for prime movers and using activation techniques may reinforce this relationship. In the case of the piriformis - it often becomes synergistically dominant for a weak/inhibited gluteus maximus and gluteus medius , but due to the variation in compesation patterns between individuals it may also become short or long. When the piriformis is long and overactive it is generally released, but NOT stretched. If the piriformis is short and overactive than you may release and stretch.
It is the author's view that muscles that are long/overactive should be released only - stretching and activation techniques should be avoided.
Specific Techniques for the Piriformis:
Piriformis Self-administered Static Release:
Piriformis Self-Administered Active Release:
Piriformis Static Stretch and Modifications:
Self Administered SI Joint Mobilization (May be an effective active stretch for the piriformis)
Bibliography:
- * 3. Phillip Page, Clare Frank , Robert Lardner , Assessment and Treatment of Muscle Imbalance: The Janda Approach © 2010 Benchmark Physical Therapy, Inc., Clare C. Frank, and Robert Lardner
6. Dr. Mike Clark & Scott Lucette, “_NASM Essentials of Corrective Exercise Training_” © 2011 Lippincott Williams & Wilkins
9. Donald A. Neumann, “Kinesiology of the Musculoskeletal System: Foundations of Rehabilitation – 2nd Edition” © 2012 Mosby, Inc.
12. Michael A. Clark, Scott C. Lucett, _NASM Essentials of Personal Training: 4th Edition_, © 2011 Lippincott Williams and Wilkins
15. Leon Chaitow, _Muscle Energy Techniques: Third Edition_, © Elsevier 2007
18. Tom Myers, _Anatomy Trains: Second Edition_. © Elsevier Limited 2009
21. Shirley A Sahrmann, _Diagnoses and Treatment of Movement Impairment Syndromes,_ © 2002 Mosby Inc.
24. David G. Simons, Janet Travell, Lois S. Simons, _Travell & Simmons’ Myofascial Pain and Dysfunction, The Trigger Point Manual, Volume 1. Upper Half of Body: Second Edition_,© 1999 Williams and Wilkens
27. Cynthia C. Norkin, D. Joyce White, Measurement of Joint Motion: A Guide to Goniometry – Third Edition. © 2003 by F.A. Davis Company
30. Cynthia C. Norkin, Pamela K. Levangie, _Joint Structure and Function: A Comprehensive Analysis: Fifth Edition_ © 2011 F.A. Davis Company
33. Florence Peterson Kendall, Elizabeth Kendall McCreary, Patricia Geise Provance, Mary McIntyre Rodgers, William Anthony Romani__,_ Muscles: Testing and Function with Posture and Pain: Fifth Edition © 2005 Lippincott Williams & Wilkins_
36. Andrew Biel, Trail Guide to the Human Body: 4th Edition, © 2010
39. Carolyn Richardson, Paul Hodges, Julie Hides. Therapeutic Exercise for Lumbo Pelvic Stabilization – A Motor Control Approach for the Treatment and Prevention of Low Back Pain: 2nd Edition (c) Elsevier Limited, 2004
42. Craig Liebenson, Rehabilitation of the Spine: A Practitioner’s Manual, (c) 2007 Lippincott Williams & Wilkins
45. Stuart McGill, Low Back Disorders: Second Ediction © 2007 Stuart M. McGill
48. Robert Schleip, Thomas W. Findley, Leon Chaitow and Peter A. Huijing. Fascia: The Tensional Network of the Human Body. (c) 2012 Elsevier Ltd.
Bibliography:
© 2014 Brent Brookbush
Questions, comments, and criticisms are welcome and encouraged.