- Email: [email protected]
Anatomy and Physiology of the Pelvic Floor
A n a t o m y an d P h y s i o l o g y of the Pelvic Floor Sarah M. Eickmeyer,
MD
KEYWORDS Pelvic floor muscles Levator ani Pelvic girdle Sacroiliac joint Pubic symphysis KEY POINTS The bony anatomy of the pelvic girdle consists of 3 bones—the 2 innominate bones and the sacrum, and 3 joints—the sacroiliac joints and the pubic symphysis. The pelvic floor muscles are comprised mainly of the levator ani muscles with somatic innervation from the lumbosacral plexus. The bony and muscular pelvis is highly interconnected to the hip and gluteal musculature, which together provide support to the internal organs and core muscles. Pelvic floor physiology is centered on bladder and bowel control, sexual functioning, and pregnancy.
INTRODUCTION
Understanding the anatomic relationship of the pelvic floor muscles with the pelvic girdle, spine, and hips aids the rehabilitation provider in diagnosis, management, and appropriate referrals. This article reviews the anatomy of the pelvic girdle, the pelvic floor musculature, and its innervation, and highlights the normal physiology of the pelvic floor. ANATOMY OF THE PELVIC FLOOR
The pelvic floor is composed of muscles, ligaments, and fascia that act as a sling to support the bladder, reproductive organs, and rectum. This sling of soft tissue is enclosed by the bony scaffolding of the pelvis, formed by 2 innominate bones made from the ilium, ischium, and pubis, which articulate with the sacrum posteriorly and each other anteriorly (Fig. 1). Extending from the sacrum is the coccyx, which acts as an important ligamentous and tendinous anchor. The stability of the articulating surfaces of the pelvis is thought to arise through mechanisms termed “force closure” and “form closure.” Force closure is achieved
The author has nothing to disclose. Department of Rehabilitation Medicine, University of Kansas, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA E-mail address: [email protected] Phys Med Rehabil Clin N Am - (2017) -–http://dx.doi.org/10.1016/j.pmr.2017.03.003 1047-9651/17/ª 2017 Elsevier Inc. All rights reserved.
pmr.theclinics.com
2
Eickmeyer
Fig. 1. The bony pelvic girdle consists of the 2 innominate bones and the sacrum, which are connected by 2 posterior sacroiliac joints and 1 anterior pubic symphysis joint.
through the interlocking of the ridges and grooves of the bony joint surfaces in the pelvis, whereas form closure is achieved through the compressive forces of the muscles, ligaments, and fascia, providing passive stability.1,2 In the posterior pelvic ring, there are 2 sacroiliac joints. The anterior sacroiliac ligaments, composed of the anterior longitudinal ligament, the anterior sacroiliac ligament, and the sacrospinous ligament, stabilize the joint by resisting upward movement of the sacrum and lateral movement of the ilium. The posterior sacroiliac ligaments are made up by the short and long dorsal sacroiliac ligaments, the supraspinous ligament, the iliolumbar ligament, and the sacrotuberous ligament. These ligaments function to resist downward and upward movement of the sacrum and medial motion of the ilium. Of note, the long dorsal sacroiliac ligament is believed to be a source of posterior pelvic pain owing to the forces transmitted from the sacroiliac joints and hip joint to the nociceptors and proprioceptors within the ligament.3 Anteriorly, the pubic symphysis is a cartilaginous joint between the 2 pubic bones reinforced by superior, inferior, anterior, and posterior ligaments. Functionally, it resists tension, shearing, and compression, and is subject to great mechanical stress as it widens during pregnancy. The superficial pelvic floor muscles are the bulbospongiosus, ischiocavernosus, and superficial and deep transverse perineal muscles. The deep pelvic floor muscles that line the inner walls of the pelvis are the levator ani and coccygeus that, along with the endopelvic fascia, comprise the pelvic diaphragm (Table 1). The levator ani is composed of 3 muscles—the puborectalis, pubococcygeus, and iliococcygeus (Fig. 2). The pubococcygeus is located most anteriorly. It originates from both the posterior pubic bone and the anterior portion of the arcus tendineus; it inserts into the anococcygeus ligament and the coccyx. The iliococcygeus is the posterior part of the levator ani. It originates from the posterior part of the arcus tendineus and ischial spine and attaches along the anococcygeal raphe and coccyx. Last, the puborectalis is located below the pubococcygeus and forms a U-shaped sling around the rectum. Its sphincterlike action pulls the anorectal junction forward, contributing to continence.
Anatomy and Physiology of the Pelvic Floor
Table 1 Pelvic floor musculature anatomic origins, insertions, innervation and function Muscle
Origin
Insertion
Puborectalis
Pubic symphysis
Pubic symphysis
Pubococcygeus Posterior pubic Anococcygeus bone and arcus ligament and tendineus coccyx
Innervation
Function Raise the pelvic floor
S3–5, direct innervation from sacral nerve roots
Maintains floor tone in upright position
Iliococcygeus
Ischial spine and Anococcygeal arcus tendineus raphe and coccyx
Voluntary control of urination
Coccygeus
Ischial spine
Lower sacral and upper coccygeal bones
Support of fetal head
Piriformis
Anterior sacrum
PosteriorS1-2 via Nerve Lateral rotation, surface greater to Piriformis Abduction of trochanter thigh. Retroversion of pelvis
Obturator Internus
Pelvic surface of ilium, ischium, and obturator membrane
Posterior L5, S1-2 via surface greater Nerve to trochanter Obturator internus
Lateral rotator of thigh
The coccygeus muscle is triangular in shape, reinforcing the posterior pelvic floor by arising from the ischial spine and inserting on the lower sacral–coccygeal bones and is contiguous with the sacrospinous ligament. The perineal body or central perineal tendon is located between the vagina and anus. This is a site where the pelvic muscles and sphincters converge to provide support to the pelvic floor. Rupture of this entity during childbirth can lead to pelvic organ prolapse. Lining the lateral walls of the pelvis, the piriformis arises from the anterior sacrum, with the sacrotuberous ligament and attaches on the superior border of the greater
Fig. 2. The muscles of the (A) superficial pelvic floor and (B) deep pelvic floor. (From Prather H, Dugan S, Fitzgerald C, et al. Review of anatomy, evaluation, and treatment of musculoskeletal pelvic floor pain in women. PM R 2009;1:349; with permission.)
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trochanter. When the sacrum is fixed, the piriformis laterally rotates an extended thigh, or abducts a flexed thigh. If the femurs are fixed, it can retrovert the pelvis. The obturator internus, also a lateral rotator of the thigh, arises from the pelvic surfaces of the ilium, ischium, and obturator membrane. It too attaches just distally to the piriformis on the greater trochanter. The pelvic floor muscles receive innervation through somatic, visceral, and central pathways. Skin innervation of the lower trunk, perineum, and proximal thigh is mediated through the iliohypogastric, ilioinguinal, and genitofemoral nerves (L1-L3). Perhaps the most clinically relevant nerve to this article is the pudendal nerve and its branches (Fig. 3). Arising from the ventral branches of S2-S4 of the sacral plexus, the pudendal nerve passes between the piriformis and coccygeal muscle as it traverses through the greater sciatic foramen, over the spine of the ischium, and back into the pelvis through the lesser sciatic foramen. It courses along the lateral wall of the ischiorectal fossa where it is contained in a sheath of the obturator fascia termed the pudendal (or Alcock’s) canal. There are 3 main terminal branches of the pudendal nerve—the inferior rectal nerve (which typically originates proximal to Alcock’s canal), the perineal nerve, and the dorsal nerve of the penis/clitoris. The pudendal nerve innervates the penis/clitoris, the bulbospongiosus and ischiocavernosus muscles, the perineum, the anus, the external anal sphincter, and the urethral sphincter. This nerve contributes to external genital sensation, continence, orgasm, and ejaculation. Muscles of the levator ani are thought to have direct innervation from sacral nerve roots S3-S5.4 PHYSIOLOGY OF THE PELVIC FLOOR
The pelvic floor muscles function to support the pelvic organs by coordinated contraction and relaxation.5 The pelvic floor provides active support through a constant state
Fig. 3. Innervation of the pelvic floor. (Copyright ª 2017. Used with permission of Elsevier. All rights reserved. www.netterimages.com.)
Anatomy and Physiology of the Pelvic Floor
of muscular contraction and passive support from the surrounding connective tissue and fascia. With an increase in intraabdominal pressure, the pelvic floor muscles reflexively contract with upward movement and closure of the vagina and urethral and anal sphincters. This action is important for maintaining continence. Pelvic floor relaxation occurs only briefly and intermittently during the processes of normal micturition and defecation. Micturition occurs when the bladder detrusor contracts and the urethral sphincter relaxes through involuntary autonomic nervous control, mainly under parasympathetic influences. During the same time, the pelvic floor muscles also voluntarily relaxes— chiefly the pubococcygeus of the levator ani muscle.6 The coordination of these muscular actions is essential to maintain urinary continence and allow for micturition in a socially acceptable time and place. Defecation occurs when the anal sphincter and puborectalis muscles simultaneously relax, thereby opening the rectoanal angle and allowing feces to pass. In addition, the abdominal muscles contract during a Valsalva action to increase abdominal pressure.6 The relaxation of the anal sphincter is reflexive through the autonomic nervous system, mainly under parasympathetic control. The pelvic floor muscles and abdominal muscles are under voluntary control to allow defecation to occur in a socially acceptable time and place, similar to micturition. Normal sexual function is coordinated by the pelvic floor muscles, genitalia, and autonomic nervous system. For females during the excitement phase, psychological and physical factors initiate arousal, generalized vasocongestion, and lubrication of the vaginal introitus from Bartholin’s glands. During sexual orgasm, the pelvic floor muscles, anal sphincter, and uterus undergo repeated muscle contractions occurring at 0.8-second intervals; this action is coordinated via a spinal cord reflex from the pudendal nerve via S2-S4 sacral segments to the perineum and external genitalia.7 In males, erection is under parasympathetic control, allowing the smooth muscle of the corpus cavernosa to relax and fill with blood, while the perineal striated pelvic floor muscles contracts to promote rigidity. Seminal emission is under sympathetic control as the ejaculate moves into the proximal urethra. Ejaculation is mainly a spinal cord reflex as the semen forcefully expulses from the urethra.7 Thus, both female and male sexual response is under control of the autonomic nervous system, with the parasympathetic division responsible for the excitement phase and the sympathetic division responsible for the orgasm phase. Many musculoskeletal changes occur during pregnancy to accommodate for the growing fetus and prepare the woman’s body for childbirth.8,9 In addition to the increase in body mass, the abdominal muscles lengthen, there is an increase in lumbar lordosis, an increase in the anterior pelvic tilt, an increase in the pelvic width, and the center of gravity shifts anteriorly as the fetus grows. Hormonal changes also increase joint laxity. All of these changes lead to an increased demand being placed on the hip extensors, hip abductors, ankle plantar flexors, and the pelvic floor muscles. In 2005, the International Continence Society presented a standardized terminology for pelvic floor muscles function and dysfunction.5 The pelvic floor muscles function by coordinated contraction and relaxation as a unit. Voluntary contraction is when the patient can contract the pelvic floor muscles on demand; voluntary relaxation is when the patient can relax the pelvic floor muscles on demand after a contraction. Involuntary contraction of the pelvic floor muscles occurs during an increase in intraabdominal pressure to prevent incontinence, such as during a cough. Involuntary relaxation occurs during a strain or Valsalva maneuver to allow for normal micturition or defecation. Contraction and relaxation can be observed during the pelvic floor physical examination, as described elsewhere. Based on examination of pelvic floor muscles, the
5
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Eickmeyer
following conditions have been defined by the International Continence Society. Normal pelvic floor muscles refers to muscles that can voluntarily and involuntarily contact with normal strength and relax completely. Overactive pelvic floor muscles (also sometimes termed nonrelaxing pelvic floor muscles) do not relax and may paradoxically contract when relaxation is needed, such as during micturition or defecation. Underactive pelvic floor muscles (also called noncontracting pelvic floor muscles) cannot voluntarily contact when desired. Nonfunctioning pelvic floor muscles refer to no palpable pelvic floor muscle action and can be based on a noncontracting, nonrelaxing pelvic floor where the muscles are both weak and hypertonic. These categories can be helpful for generating a differential diagnosis for possible etiologies of pelvic floor dysfunction. SUMMARY
A clear understanding of the bones, muscles, and nerves of the pelvic floor sets the stage for understanding normal and abnormal function of bowel and bladder continence, sexual functioning, and pregnancy-related issues.10 REFERENCES
1. Pool-Goudzwaard AL, Vleeming A, Stoeckart R, et al. Insufficient lumbopelvic stability: a clinical, anatomical and biomechanical approach to ’a-specific’ low back pain. Man Ther 1998;3:12–20. 2. Vleeming A, Stoeckart R, Volkers AC, et al. Relation between form and function in the sacroiliac joint. Part I: clinical anatomical aspects. Spine 1990;15:130–2. 3. Vleeming A, Pool-Goudzwaard AL, Hammudoghlu D, et al. The function of the long dorsal sacroiliac ligament: its implication for understanding low back pain. Spine 1995;21:556–62. 4. Barber MD, Bremer RE, Thor KB, et al. Innervation of the female levator ani muscles. Am J Obstet Gynecol 2002;187(1):64–71. 5. Messelink B, Benson T, Berghmans B, et al. Standardization of terminology of pelvic floor muscle function and dysfunction: report from the pelvic floor clinical assessment group of the International Continence Society. Neurourol Urodyn 2005;24:374–80. 6. Rocca Rossetti S. Functional anatomy of pelvic floor. Arch Ital Urol Androl 2016; 88(1):28–37. 7. Boron WF, editor. Medical physiology. 1st edition. Philadelphia: Saunders; 2003. 8. Foti T, Davids JR, Bagley A. A biomechanical analysis of gait during pregnancy. J Bone Joint Surg Am 2000;82:625–32. 9. Gilleard W, Crosbie J, Smith R. Effect of pregnancy on trunk range of motion when sitting and standing. Acta Obstet Gynecol Scand 2002;81:1011–20. 10. Prather H, Dugan S, Fitzgerald C, et al. Review of anatomy, evaluation, and treatment of musculoskeletal pelvic floor pain in women. PM R 2009;1:346–58.
MD
KEYWORDS Pelvic floor muscles Levator ani Pelvic girdle Sacroiliac joint Pubic symphysis KEY POINTS The bony anatomy of the pelvic girdle consists of 3 bones—the 2 innominate bones and the sacrum, and 3 joints—the sacroiliac joints and the pubic symphysis. The pelvic floor muscles are comprised mainly of the levator ani muscles with somatic innervation from the lumbosacral plexus. The bony and muscular pelvis is highly interconnected to the hip and gluteal musculature, which together provide support to the internal organs and core muscles. Pelvic floor physiology is centered on bladder and bowel control, sexual functioning, and pregnancy.
INTRODUCTION
Understanding the anatomic relationship of the pelvic floor muscles with the pelvic girdle, spine, and hips aids the rehabilitation provider in diagnosis, management, and appropriate referrals. This article reviews the anatomy of the pelvic girdle, the pelvic floor musculature, and its innervation, and highlights the normal physiology of the pelvic floor. ANATOMY OF THE PELVIC FLOOR
The pelvic floor is composed of muscles, ligaments, and fascia that act as a sling to support the bladder, reproductive organs, and rectum. This sling of soft tissue is enclosed by the bony scaffolding of the pelvis, formed by 2 innominate bones made from the ilium, ischium, and pubis, which articulate with the sacrum posteriorly and each other anteriorly (Fig. 1). Extending from the sacrum is the coccyx, which acts as an important ligamentous and tendinous anchor. The stability of the articulating surfaces of the pelvis is thought to arise through mechanisms termed “force closure” and “form closure.” Force closure is achieved
The author has nothing to disclose. Department of Rehabilitation Medicine, University of Kansas, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA E-mail address: [email protected] Phys Med Rehabil Clin N Am - (2017) -–http://dx.doi.org/10.1016/j.pmr.2017.03.003 1047-9651/17/ª 2017 Elsevier Inc. All rights reserved.
pmr.theclinics.com
2
Eickmeyer
Fig. 1. The bony pelvic girdle consists of the 2 innominate bones and the sacrum, which are connected by 2 posterior sacroiliac joints and 1 anterior pubic symphysis joint.
through the interlocking of the ridges and grooves of the bony joint surfaces in the pelvis, whereas form closure is achieved through the compressive forces of the muscles, ligaments, and fascia, providing passive stability.1,2 In the posterior pelvic ring, there are 2 sacroiliac joints. The anterior sacroiliac ligaments, composed of the anterior longitudinal ligament, the anterior sacroiliac ligament, and the sacrospinous ligament, stabilize the joint by resisting upward movement of the sacrum and lateral movement of the ilium. The posterior sacroiliac ligaments are made up by the short and long dorsal sacroiliac ligaments, the supraspinous ligament, the iliolumbar ligament, and the sacrotuberous ligament. These ligaments function to resist downward and upward movement of the sacrum and medial motion of the ilium. Of note, the long dorsal sacroiliac ligament is believed to be a source of posterior pelvic pain owing to the forces transmitted from the sacroiliac joints and hip joint to the nociceptors and proprioceptors within the ligament.3 Anteriorly, the pubic symphysis is a cartilaginous joint between the 2 pubic bones reinforced by superior, inferior, anterior, and posterior ligaments. Functionally, it resists tension, shearing, and compression, and is subject to great mechanical stress as it widens during pregnancy. The superficial pelvic floor muscles are the bulbospongiosus, ischiocavernosus, and superficial and deep transverse perineal muscles. The deep pelvic floor muscles that line the inner walls of the pelvis are the levator ani and coccygeus that, along with the endopelvic fascia, comprise the pelvic diaphragm (Table 1). The levator ani is composed of 3 muscles—the puborectalis, pubococcygeus, and iliococcygeus (Fig. 2). The pubococcygeus is located most anteriorly. It originates from both the posterior pubic bone and the anterior portion of the arcus tendineus; it inserts into the anococcygeus ligament and the coccyx. The iliococcygeus is the posterior part of the levator ani. It originates from the posterior part of the arcus tendineus and ischial spine and attaches along the anococcygeal raphe and coccyx. Last, the puborectalis is located below the pubococcygeus and forms a U-shaped sling around the rectum. Its sphincterlike action pulls the anorectal junction forward, contributing to continence.
Anatomy and Physiology of the Pelvic Floor
Table 1 Pelvic floor musculature anatomic origins, insertions, innervation and function Muscle
Origin
Insertion
Puborectalis
Pubic symphysis
Pubic symphysis
Pubococcygeus Posterior pubic Anococcygeus bone and arcus ligament and tendineus coccyx
Innervation
Function Raise the pelvic floor
S3–5, direct innervation from sacral nerve roots
Maintains floor tone in upright position
Iliococcygeus
Ischial spine and Anococcygeal arcus tendineus raphe and coccyx
Voluntary control of urination
Coccygeus
Ischial spine
Lower sacral and upper coccygeal bones
Support of fetal head
Piriformis
Anterior sacrum
PosteriorS1-2 via Nerve Lateral rotation, surface greater to Piriformis Abduction of trochanter thigh. Retroversion of pelvis
Obturator Internus
Pelvic surface of ilium, ischium, and obturator membrane
Posterior L5, S1-2 via surface greater Nerve to trochanter Obturator internus
Lateral rotator of thigh
The coccygeus muscle is triangular in shape, reinforcing the posterior pelvic floor by arising from the ischial spine and inserting on the lower sacral–coccygeal bones and is contiguous with the sacrospinous ligament. The perineal body or central perineal tendon is located between the vagina and anus. This is a site where the pelvic muscles and sphincters converge to provide support to the pelvic floor. Rupture of this entity during childbirth can lead to pelvic organ prolapse. Lining the lateral walls of the pelvis, the piriformis arises from the anterior sacrum, with the sacrotuberous ligament and attaches on the superior border of the greater
Fig. 2. The muscles of the (A) superficial pelvic floor and (B) deep pelvic floor. (From Prather H, Dugan S, Fitzgerald C, et al. Review of anatomy, evaluation, and treatment of musculoskeletal pelvic floor pain in women. PM R 2009;1:349; with permission.)
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Eickmeyer
trochanter. When the sacrum is fixed, the piriformis laterally rotates an extended thigh, or abducts a flexed thigh. If the femurs are fixed, it can retrovert the pelvis. The obturator internus, also a lateral rotator of the thigh, arises from the pelvic surfaces of the ilium, ischium, and obturator membrane. It too attaches just distally to the piriformis on the greater trochanter. The pelvic floor muscles receive innervation through somatic, visceral, and central pathways. Skin innervation of the lower trunk, perineum, and proximal thigh is mediated through the iliohypogastric, ilioinguinal, and genitofemoral nerves (L1-L3). Perhaps the most clinically relevant nerve to this article is the pudendal nerve and its branches (Fig. 3). Arising from the ventral branches of S2-S4 of the sacral plexus, the pudendal nerve passes between the piriformis and coccygeal muscle as it traverses through the greater sciatic foramen, over the spine of the ischium, and back into the pelvis through the lesser sciatic foramen. It courses along the lateral wall of the ischiorectal fossa where it is contained in a sheath of the obturator fascia termed the pudendal (or Alcock’s) canal. There are 3 main terminal branches of the pudendal nerve—the inferior rectal nerve (which typically originates proximal to Alcock’s canal), the perineal nerve, and the dorsal nerve of the penis/clitoris. The pudendal nerve innervates the penis/clitoris, the bulbospongiosus and ischiocavernosus muscles, the perineum, the anus, the external anal sphincter, and the urethral sphincter. This nerve contributes to external genital sensation, continence, orgasm, and ejaculation. Muscles of the levator ani are thought to have direct innervation from sacral nerve roots S3-S5.4 PHYSIOLOGY OF THE PELVIC FLOOR
The pelvic floor muscles function to support the pelvic organs by coordinated contraction and relaxation.5 The pelvic floor provides active support through a constant state
Fig. 3. Innervation of the pelvic floor. (Copyright ª 2017. Used with permission of Elsevier. All rights reserved. www.netterimages.com.)
Anatomy and Physiology of the Pelvic Floor
of muscular contraction and passive support from the surrounding connective tissue and fascia. With an increase in intraabdominal pressure, the pelvic floor muscles reflexively contract with upward movement and closure of the vagina and urethral and anal sphincters. This action is important for maintaining continence. Pelvic floor relaxation occurs only briefly and intermittently during the processes of normal micturition and defecation. Micturition occurs when the bladder detrusor contracts and the urethral sphincter relaxes through involuntary autonomic nervous control, mainly under parasympathetic influences. During the same time, the pelvic floor muscles also voluntarily relaxes— chiefly the pubococcygeus of the levator ani muscle.6 The coordination of these muscular actions is essential to maintain urinary continence and allow for micturition in a socially acceptable time and place. Defecation occurs when the anal sphincter and puborectalis muscles simultaneously relax, thereby opening the rectoanal angle and allowing feces to pass. In addition, the abdominal muscles contract during a Valsalva action to increase abdominal pressure.6 The relaxation of the anal sphincter is reflexive through the autonomic nervous system, mainly under parasympathetic control. The pelvic floor muscles and abdominal muscles are under voluntary control to allow defecation to occur in a socially acceptable time and place, similar to micturition. Normal sexual function is coordinated by the pelvic floor muscles, genitalia, and autonomic nervous system. For females during the excitement phase, psychological and physical factors initiate arousal, generalized vasocongestion, and lubrication of the vaginal introitus from Bartholin’s glands. During sexual orgasm, the pelvic floor muscles, anal sphincter, and uterus undergo repeated muscle contractions occurring at 0.8-second intervals; this action is coordinated via a spinal cord reflex from the pudendal nerve via S2-S4 sacral segments to the perineum and external genitalia.7 In males, erection is under parasympathetic control, allowing the smooth muscle of the corpus cavernosa to relax and fill with blood, while the perineal striated pelvic floor muscles contracts to promote rigidity. Seminal emission is under sympathetic control as the ejaculate moves into the proximal urethra. Ejaculation is mainly a spinal cord reflex as the semen forcefully expulses from the urethra.7 Thus, both female and male sexual response is under control of the autonomic nervous system, with the parasympathetic division responsible for the excitement phase and the sympathetic division responsible for the orgasm phase. Many musculoskeletal changes occur during pregnancy to accommodate for the growing fetus and prepare the woman’s body for childbirth.8,9 In addition to the increase in body mass, the abdominal muscles lengthen, there is an increase in lumbar lordosis, an increase in the anterior pelvic tilt, an increase in the pelvic width, and the center of gravity shifts anteriorly as the fetus grows. Hormonal changes also increase joint laxity. All of these changes lead to an increased demand being placed on the hip extensors, hip abductors, ankle plantar flexors, and the pelvic floor muscles. In 2005, the International Continence Society presented a standardized terminology for pelvic floor muscles function and dysfunction.5 The pelvic floor muscles function by coordinated contraction and relaxation as a unit. Voluntary contraction is when the patient can contract the pelvic floor muscles on demand; voluntary relaxation is when the patient can relax the pelvic floor muscles on demand after a contraction. Involuntary contraction of the pelvic floor muscles occurs during an increase in intraabdominal pressure to prevent incontinence, such as during a cough. Involuntary relaxation occurs during a strain or Valsalva maneuver to allow for normal micturition or defecation. Contraction and relaxation can be observed during the pelvic floor physical examination, as described elsewhere. Based on examination of pelvic floor muscles, the
5
6
Eickmeyer
following conditions have been defined by the International Continence Society. Normal pelvic floor muscles refers to muscles that can voluntarily and involuntarily contact with normal strength and relax completely. Overactive pelvic floor muscles (also sometimes termed nonrelaxing pelvic floor muscles) do not relax and may paradoxically contract when relaxation is needed, such as during micturition or defecation. Underactive pelvic floor muscles (also called noncontracting pelvic floor muscles) cannot voluntarily contact when desired. Nonfunctioning pelvic floor muscles refer to no palpable pelvic floor muscle action and can be based on a noncontracting, nonrelaxing pelvic floor where the muscles are both weak and hypertonic. These categories can be helpful for generating a differential diagnosis for possible etiologies of pelvic floor dysfunction. SUMMARY
A clear understanding of the bones, muscles, and nerves of the pelvic floor sets the stage for understanding normal and abnormal function of bowel and bladder continence, sexual functioning, and pregnancy-related issues.10 REFERENCES
1. Pool-Goudzwaard AL, Vleeming A, Stoeckart R, et al. Insufficient lumbopelvic stability: a clinical, anatomical and biomechanical approach to ’a-specific’ low back pain. Man Ther 1998;3:12–20. 2. Vleeming A, Stoeckart R, Volkers AC, et al. Relation between form and function in the sacroiliac joint. Part I: clinical anatomical aspects. Spine 1990;15:130–2. 3. Vleeming A, Pool-Goudzwaard AL, Hammudoghlu D, et al. The function of the long dorsal sacroiliac ligament: its implication for understanding low back pain. Spine 1995;21:556–62. 4. Barber MD, Bremer RE, Thor KB, et al. Innervation of the female levator ani muscles. Am J Obstet Gynecol 2002;187(1):64–71. 5. Messelink B, Benson T, Berghmans B, et al. Standardization of terminology of pelvic floor muscle function and dysfunction: report from the pelvic floor clinical assessment group of the International Continence Society. Neurourol Urodyn 2005;24:374–80. 6. Rocca Rossetti S. Functional anatomy of pelvic floor. Arch Ital Urol Androl 2016; 88(1):28–37. 7. Boron WF, editor. Medical physiology. 1st edition. Philadelphia: Saunders; 2003. 8. Foti T, Davids JR, Bagley A. A biomechanical analysis of gait during pregnancy. J Bone Joint Surg Am 2000;82:625–32. 9. Gilleard W, Crosbie J, Smith R. Effect of pregnancy on trunk range of motion when sitting and standing. Acta Obstet Gynecol Scand 2002;81:1011–20. 10. Prather H, Dugan S, Fitzgerald C, et al. Review of anatomy, evaluation, and treatment of musculoskeletal pelvic floor pain in women. PM R 2009;1:346–58.