The pelvis has several functions: to protect and support the pelvic viscera, allow for transference of weight bearing forces from the trunk and ground reaction forces from the lower extremities, provide support for the fetus and house the birth canal, and provide attachment sites for ligaments and muscles of the lower extremities and trunk [14]. The body’s center of gravity is located within the pelvis at the second sacral segment. The pelvis is the hub or center of stability for control of movement for the entire body.

The innominate bones that are made up of the ilium, ischium, and pubis are fused in adulthood. The ilia and sacrum join on either side to form the sacroiliac joints posteriorly. The sacroiliac joints are intermediate joints between a synarthrosis and diarthrosis called an amphiarthrosis which means only a small amount of movement can occur [15]. Sacroiliac joint mobility is multiplanar and varies based on the position and transfer of load [15, 16]. The main movement of the sacroiliac joints is rotation yet gliding, anteroposterior and vertical movements also occur to a lesser degree. More recent studies demonstrate that sagittal rotation movement of the sacroiliac joint is about 3.6° of movement and translation movement is 2 mm [17];however, prior studies have shown that up to 10 mm of movement can occur in the sacroiliac joint during manual medicine maneuver in normal subjects [18]. The sacroiliac joints are innervated by spinal nerve roots L4–S3.

The apex of the sacrum and the first coccyx segment attaches to create the sacrococcygeal joint. There is a sacrococcygeal fibrocartilage disc also known as the interosseus ligament . Normal movement of the sacrococcygeal joint is 15° of flexion and 13° of extension. In normal physiological movement as the sacrum extends, the apex of the coccyx moves anterior or flexes and as the sacrum flexes, the apex of the coccyx moves posterior or extends (Fig. 7.1). The sacrum comprises five fused segments, and the coccyx also comprises five fused rudimentary bones. The interosseous, dorsal sacroiliac ligaments, and anterior sacroiliac ligament stabilize the sacroiliac joints. Other accessory ligaments, such as the iliolumbar, stabilize the superior part of the joint and the sacrospinous, and sacrotuberous stabilize the inferior aspect of the sacrum. At the distal end of the coccyx, the anococcygeal ligament is the attachment site of the rectoanal angle and the levator ani.

Anteriorly at the superior rami, the pelvis joins by way of a fibrocartilaginous joint, called the pubic symphysis that has a cartilage disc in the center between thin layers of hyaline cartilage. The pubic symphysis has 3° of freedom and can also move anterior/posterior, internal/external rotation about its center axis. The sacrum articulates with the lumbar spine by way of the lumbosacral joint between the first sacral segment (S1) and the fifth lumbar vertebral segment (L5). The sacrum moves into nutation and counternutation relative to the ilium. Spinal flexion couples with sacral counternutation (or sacral extension) and spinal extension couples with sacral nutation (or sacral flexion). The femoral head articulates with the acetabulum of the innominate bones to form the hip joints. Hip flexion is coupled with the ilium moving into posterior rotation and hip extension is combined with the ilium moving into anterior rotation. Coupled motions of pelvic and hip flexion and extension are involved in establishing lordosis and kyphosis in the lower spine [15]. Thus, the spine, sacrum, coccyx, and hips all influence the function of the pelvis. Both the sacroiliac joints and pubic symphysis have little motion.

During gait, the pelvis acts as the axis where rotation of the lower extremities is balanced by rotation of the upper extremities. The pubic symphysis moves superior and inferior during gait. In one legged-stance, the pubic symphysis moves vertical [19]. Movement at the sacroiliac joint helps to decrease the shearing forces at the L5–S1 junction during the hip extension phase of gait. Gait mechanic analysis revealed that the SI joints are mobile yet stable for load transfer to occur to and the load transfers from the lumbar spine and lower extremities [20, 21].

The muscle groups that attach onto the pelvis and influence its function include the superficial and deep pelvic floor muscles, the hip adductors, extensors, flexors, and rotators, abdominals, diaphragm, and the extensors and rotators of the spine. Muscle imbalances such as weakness or impaired flexibility in any of these muscle groups can change the forces on the pelvic girdle and alter biomechanics leading to dysfunction. More specifically, altered motor control of deeper abdominal and pelvic muscles, such as the transversus abdominis, internal oblique, multifidus, respiratory diaphragm, and pelvic floor muscles can result in lumbopelvic pain and impaired pelvic mobility and stability. Lumbar spine and pelvic girdle muscle recruitment is also altered with existent low back or SIJ pain [22, 23]. Along with the large muscles overlying the SI joint, contraction of other muscles such as the transversus abdominis, the pelvic floor muscles, and the respiratory diaphragm can affect the stiffness of the spine and SIJ [24–28].

An important function of the pelvic girdle is to be able to transfer the load created by the weight of the body and gravity during functional activities including walking, transferring, and all activities of daily living. In order for this to occur efficiently, there must be form closure and force closure of the pelvic joints and effective motor control. Optimal lumbopelvic stability is a function of form closure, force closure, and neuromotor control. Form closure is passive and is produced by joints anatomically approximating congruently. Force closure is the force produced by muscular contraction, ligaments, and fascia creating compressive forces and motor control around a joint creating joint stability or locking [21]. Impairments of these mechanisms, especially at the sacroiliac joints, can cause lumbar spine or pelvic pain, instability, impaired lumbopelvic kinematics, and reduced strength and motor control [29].

Motion control of the pelvic joints requires efficient activation which is coordinated and sequenced so that activation of muscle groups and co-activation occurs resulting in the least amount of compression forces. If inefficient motion control at the pelvis occurs, excessive shearing, giving way, and bracing or stiffening of the hips, low back, pelvis, or rib cage may result [20]. Non-optimal strategies can cause an increase in intra-abdominal pressure resulting in suboptimal breathing patterns, impaired diaphragmatic excursion, increased intra-abdominal pressure, and may compromise pelvic floor muscle function and continence.

The lumbo-pelvic-hip complex helps create the core. The core has been presented as a three-dimensional box or canister comprises the respiratory diaphragm, pelvic floor and hip complex, abdominals, spinal, and gluteal muscles [30, 31]. Although there are many global (larger, longer) muscles and local (smaller, shorter) muscles involved in core stability [31], four muscle groups that contribute the most to stabilizing the box or canister are the respiratory diaphragm from above, the transversus abdominis along the sides, the mulitifidi posteriorly, and the pelvic floor from underneath. These muscles help form the core. The core provides a stable base for all extremity movement to occur [30, 32] Impaired recruitment of the pelvic floor muscles, transversus abdominis, respiratory diaphragm, and deep fibers of the lumbar multifidi can result in failure of load transfer through the pelvic girdle. Muscle recruitment and motor patterns for force closure of pelvic joints may be delayed, inhibited, or asymmetric. Repetitive strain of the lumbo-pelvic-hip passive soft tissue structures may result. Studies of patients with chronic low back pain, pelvic pain, and groin pain show delayed activation of transversus abdominis. Delayed contraction of the transversus abdominis impedes the pretensing of the thoracodorsal fascia needed for efficient pelvic stability for load transfer. Pelvic floor muscle function is important in stabilizing the pelvic girdle from underneath and overactivity in the muscles can result in weakness, impaired sequencing, and timing of activation. Force closure of the urethra, bladder stability, and motion control of the sacroiliac joints may be compromised.

Pubic symphysis disorders can include osteitis pubis, pubic symphysis diastasis or separation, or misalignment. Osteitis pubis is a chronic inflammatory pain disorder that involves the pubic bones, symphysis pubis, hip adductors, abdominal muscles, and adjacent fascia [33]. Osteitis pubis is characterized by sclerosis and bony changes at the pubic symphysis [34]. Osteitis pubis is often misdiagnosed or mismanaged and can thus be prolonged and cause disability. Symptoms can include diffuse lower abdominal and pubic pain, and often be mistaken for groin strain, abdominal strain, and bladder pain. Pain can be referred into the hip, groin, scrotum, perineum [35], or labia. Osteitis pubis can be the cause of pain with intercourse. The pain in the pubis may worsen upon running, climbing stairs, or change of positions such as standing from sitting, rolling in bed, or getting out of a car. Sports activities such as soccer and football where kicking is most prevalent can cause or worsen symptoms [33]. Postures in standing whereby the legs are asymmetrical can exacerbate symptoms. Causes of osteitis pubis include trauma [33], repeat exertional forces [33], childbirth [36], infections following urologic or gynecologic procedures [34], and muscle imbalances [33, 35]. Muscle imbalances of the abdominals and hip adductors along with the pelvic floor muscles may be a causative factor and because of their attachments on the pubis can cause uneven torque to the pubic symphysis resulting in repetitive strain . Diagnosis is based on history, physical exam, and radiographic results such as X-ray or bone scan. Palpation pain directly over the pubis, inflammation at the symphysis pubis or lower abdominal region, and a positive symphysis gap test [33] are also common diagnostic criteria. There are four classifications of osteitis pubis for athletes [33]. Stage 1 includes pain in one leg and inguinal pain in the adductors. Stage 2 involves bilateral inguinal pain. In Stage 3, there is bilateral inguinal pain upon changing positions from sitting to standing or changing directions while playing sports. Stage 4 involves pain in the adductor and abdominal muscles and referred pain to the pelvic girdle or lumbar region upon sneezing, bowel movements, and walking on even surfaces. Conservative management may include rest, nonsteroidal anti-inflammatory drugs [33], corticosteroid injections, and physical therapy. Surgery may be needed in 5–10 % of the cases [36, 37].

Pubic symphysis diastasis is a separation of the pubic symphysis that occurs during pregnancy or as a result of vaginal delivery , following osteoarthritis and long-term use of corticosteroids, pelvic trauma, and high velocity injuries [34]. Horseback riding has also been found to be a cause [34]. There may also be injury to the ligaments of the sacroiliac joints that lead to chronic pelvic pain [38]. The short hip adductors and obturator externus function together as a unit. Together they can produce a distraction force at the pubic rami and if chronically tight can become a predisposing factor. The physiologic widening of the pubic symphysis is considered to be a maximum of 10 mm especially during pregnancy, and separation of 1 cm is often symptomatic causing pain [39]. Pubic symphysis diastasis is diagnosed via history, physical exam, and an anterior-posterior pelvic X-ray. Physical exam may reveal weakness in the hip flexors, quadriceps, and hamstrings due to pain. Difficulty with transfers and position changes may be reported and ambulation may be impaired. Symptoms include groin pain, hip pain, swelling over the pubis, sacroiliac joint pain, pubic or groin pain upon leg movement and walking. If unresolved, overactive pelvic floor muscles, abdominal pain, and hip myalgia can result [40]. Conservative management can include rest, analgesia, wearing an abdominal/pelvic binder or pelvic stabilizing belt [41]. Physical therapy is also prescribed. A specific rehabilitation program that focuses on core strengthening and pelvic floor muscle rehabilitation improves the prognosis of decreased pain, improved function and mobility [42]. Overactive pelvic floor muscles are inherently weak because when muscles are shortened the length–tension relationship is altered and are at a disadvantage of optimal force production upon contraction. Ultimately, the goal of rehabilitation is to achieve full pelvic floor muscle length, improved resting tone, resolve pain and myofascial trigger points, and then strengthen the pelvic floor muscle through its full excursion or range of motion.

Pubic symphysis misalignment or unleveling or subluxation is another disorder. Unleveling of the pubic symphysis is superior or inferior (cephalad or caudal), also known as a shear [42] (Fig. 7.2). Pubic shears commonly occur with other pelvic innominate rotations or upslip and downslip dysfunctions. An innominate rotation is when one side of the pelvis is rotated anterior or posterior compared to the other side, thus labeled anterior innominate rotation or posterior innominate rotation . A pelvic upslip is when one side of the pelvis is higher than the other side and this is measured by comparing the heights of the iliac crests manually [42]. Innominate rotations and a pelvic upslip or downslip dysfunction can cause pubic symphysis misalignments. Direct causes of superior sheared pubic symphysis include upward forces through the ipsilateral leg, falls onto the ischial tuberosity, weak hip abductors, and tight surgical scars in the suprapubic region such as cesarean incision scar. Inferior shears of the pubic symphysis are caused by lift upward of the body with a fixated foot, tight hip adductors, and pelvic floor muscle tension. The hip adductors have an immediate effect on superior and inferior forces placed on the pubic rami thus an imbalance or chronic tightness can be a contributing factor. The presenting symptom for pubic misalignment is groin pain. Some associated symptoms may include bladder urgency or frequency, urethra pain, clitoral pain, scrotal or penile pain. Superior or inferior pubic symphysis shears alter the anterior and posterior hip rotation motion that occurs with gait. During the normal gait pattern, the pubic symphysis acts as an anterior axis for alternating hip rotation [43, 44]. Perpetual misalignment of the pubic symphysis can eventually result in osteitis pubis, hip pain, and chronic pelvic pain. Physical therapy management includes pubic symphyseal corrective techniques such as muscle energy techniques and direct mobilizations and soft tissue mobilization to the pelvic floor muscles, hip adductors, suprapubic region, and pubic ligaments.

Pubic symphysis compression is caused by trauma, hip hyperadduction or internal rotation forces and pain in the pubis worsens with ascending stairs and walking. Pelvic floor muscle dysfunction such as tightness, spasm, and overactivity is also a cause. Pain presents at the symphysis, perineum, inner thigh, or hip region. Physical therapy management includes pubic symphyseal mobilization such as decompression or lateral distraction techniques and soft tissue mobilization to the pelvic floor muscles, hip adductors, suprapubic region, and pubic ligaments [43].

Despite pubic symphysis pain disorders referring pain into the pelvic girdle, scrotum, labia, and perineum, the pelvic floor muscles are a frequently overlooked factor in pubic symphysis disorders. Understanding the anatomical connections and relationships are important factors in the physical examination. Two superficial pelvic floor muscles, the bulbocavernosus and ischiocavernosus, and one deep pelvic floor muscle, the pubococcygeus, attach onto the inferior pubis and can be involved in contributing to pubic symphysis pain. The abdominal muscles such as the rectus abdominis and transversus abdominis together with the internal oblique attach to the superior aspect of the pubic symphysis. The abdominal muscles and adductors act antagonistically to the pelvic floor muscles in daily functional activities. When muscle imbalances are present, it can predispose the symphysis pubis to mechanical traction microtrauma such as in osteitis pubis. Overactive pelvic floor muscles will place an abnormal inferior tension or pull on the pubis, especially if only one side of the pelvic floor muscles is tense or shortened. This can contribute to causes and perpetuation of pubic symphysis dysfunction. Likewise, a superior pubic shear will place abnormal tension on the pelvic floor muscles. Over time, if not corrected the pelvic floor muscles may remain in a contracted state and become chronically overactive. Also, the pelvic floor muscles engage as a protective guarding/mechanism as a response to pubic symphysis pain and inflammation. Likewise, the hip adductors can engage as a protective guarding/mechanism.

The hip adductor fascia is continuous with the pelvic floor muscles. The pubococcygeus muscle , one of the levator ani muscles, is also referred to as the pubovisceral can be further subdivided into the puboperinealis, pubovaginalis, and puboanalis. All of these collectively originate on the inner surface of the pubic symphysis and insert into the perineal body, vaginal wall near the level of the urethra, and into the groove between the external and internal anal sphincter. The puborectalis also originates from the pubic bone and forms a supportive sling around the anus.

Pubic symphysis disorders may cause inhibition and weakness of the transversus abdominis, external oblique, and rectus abdominis muscles due to inflammation and pain in the region. Inflammation and pain in a joint can cause inhibition of the surrounding joint muscles. In order for the trunk and pelvis to gain stability, the pelvic floor muscles would be recruited and shortened and remain contracted resulting in overactivity.

Hip impingement, also known as femoroacetabular impingement (FAI ), occurs when there is abnormal contact between the proximal femur and acetabulum during motion. Causes of abnormal contact between the proximal femur and acetabulum include muscle imbalances such as a tight psoas muscle and weakened hip extensors or deep rotators pulling the femoral head anteriorly, prior trauma such as femoral neck fractures, or as a result of childhood diseases such as Legg-Calve-Perthes Disease. Even subtle morphologic abnormalities have been seen in active patients that affect either the acetabulum or proximal femur [45]. The symptoms of impingement include medial groin pain, deep hip pain, inner thigh pain, pain along the tensor fascia latae, clicking, locking, and sharp pains [46]. Pain may worsen upon pivoting or turning towards the affected side. Groin pain on hip flexion, adduction, and internal rotation (FADIR) worsen the pain and hip impingement sign test is assessed in this position by orthopedists, physical therapists, athletic trainers, and physiatrists. Resisted hip flexion may also bring on symptoms and a decrease in hip internal rotation range of motion is usually noted. As the hip flexes, the femur abuts on the acetabular rim causing the symptoms of impingement. Recurrence of this can result in acetabular labrum injury such as labral tears and avulsion or shearing of the cartilage. Hip impingement can cause continued deterioration and lead to early onset of hip osteoarthritis and functional limitations. Tightness of the iliopsoas, quadriceps, tensor fascia latae, deep hip rotators, and pelvic floor muscles are usually concurrent issues. Hip impingement alters hip and pelvic biomechanics during gait [47]. There is a compensatory increased posterior pelvic rotation during active end range hip flexion causing a repeated pull of the pelvic floor muscles [48]. As the pelvic innominate rotates posteriorly, the pelvic floor muscles are tensioned anteriorly. Over time, this constant pulling could cause stress–strain on the pelvic floor muscles leading to overactivity of pelvic floor muscles. Conservative treatment includes analgesics, intra-articular glucocorticosteroid injections, activity modification, and physical therapy [49]. Surgical approaches include arthroscopic or open surgical dissection to debride, repair labrum and chondral surfaces, and address any boney deformities.

Studies show there is a relationship between hip function and pelvic floor muscle function such as seen in a case series of patients with labral tears as a comorbidity of low back and pelvic girdle pain [50]. The deep hip rotators include the piriformis, inferior and superior gemelli, and obturator internus and externus. Patients with chronic pelvic pain received fluoroscopy-guided anesthetic injections into the obturator externus muscle, a deep hip rotator, and 82 % found improvement in their pelvic pain [49].

Acetabular labral tears are a source of hip pain, yet there may be concomitant pelvic girdle and low back pain [51, 52]. The labrum is a cartilaginous ring anchored anteriorly and posteriorly to the transverse ligament and capsule on the acetabular periphery . It aids to the stability of the hip joint by deepening the acetabulum and increasing the surface contact area and distributing ground reactive forces [52]. Labral tears, therefore, may destabilize the hip joint by compromising the seal it provides to the joint, allow for higher stresses to the hip joint, and leading to joint deterioration. Labral tears are usually the result of repetitive sports injuries, torsional movements, and frequent movements into external rotation combined with excessive hip abduction or extension yet can also be due to trauma such as motor vehicle accidents or falls. Structural risk factors include history of hip dysplasia, femoral anteversion, acetabular retroversion, and hip impingement syndrome [52]. Repeated microtrauma over time can also lead to labral tears . Common clinical findings of labral tears include anterior hip pain, groin pain, deep buttock pain, greater trochanter pain, lateral ischial tuberosity pain, clicking, giving way, and locking. There is noted reduced hip range of motion of rotation, flexion, adduction, and abduction. Testing for an anterior labral tear occurs by bringing the hip into end range flexion, internal rotation, and adduction and posterior labral tears are tested in extension, abduction, and internal rotation [52]. A positive test provokes pain or a click. A labral tear is confirmed via magnetic resonance imaging (MRI), magnetic resonance arthrography (MRA), or arthroscopy. Treatment consists of rest, nonsteroidal anti-inflammatory agents, and physical therapy. Surgical intervention involves arthroscopic debridement of the labral tear and repair of associated structures [52].

Hip labral tears have been found to be an etiologic factor in vulvar pain syndromes such as vulvodynia with concurrent overactive pelvic floor muscles. In a preliminary study by Coady et al. [53], 40 women with suspected hip pathology and unprovoked vestibulodynia and/or clitorodynia had anterior labral tears confirmed via MRI. Physical therapy focused primarily on hip rehabilitation proved useful with 39 % reporting improvement in vulvar pain and 7 patients that underwent arthroscopic surgical labral repair reported moderate to marked improvement in both hip and vulvar pain. To better understand how hip and pelvic floor muscles impact one another and how hip dysfunction can cause pelvic floor muscle overactivity one must appreciate the anatomical and functional relationships of the hip and pelvic floor muscles. The fascia covering the pelvic floor muscles is continuous with endopelvic fascia above, perineal fascia below, and obturator fascia laterally [54]. Thus, there is a direct relationship between the hip and the pelvic floor muscles via the fascia. Thickening in the obturator fascia is called the arcus tendinous fascia pelvis and extends from the pubis anteriorly to the ischial spine and provides attachment to the paravaginal connective tissue. The pubococcygeus originates on the fascia that surrounds the obturator internus. Arising from an adjacent location on the pubis but extending superior to the arcus tendinous fascia pelvis is a thickening of levator ani fascia called arcus tendinous levator ani, which is the origin to the levator ani muscle [54].

The role of the pelvic floor muscles to help create an anchor for the deep stabilizers of the hip is important for optimizing the power of the large hip musculature to both control stability and power for descent and ascent in a squat maneuver and for stair climbing.

Pelvic obliquity is an unleveling or asymmetry of the pelvic girdle bones (Fig. 7.3). One side of pelvis is higher than the other vertically. This can be measured manually by the examiner placing one hand on the posterior superior aspects of the iliac crests and measuring for height differentiation or via X-rays [55, 56]. Causes of pelvic obliquity include leg length discrepancy, hip dysfunction, structural scoliosis, SIJD, visceral dysfunction, muscle imbalances, trauma, falls, jumping on an extended knee or as a combination of two or more of these causes [57, 43]. The superior innominate shear, or the elevated side, is referred to as an innominate upslip dysfunction. The three boney landmarks of the pelvis, such as the iliac crest, the posterior superior iliac spine, and the pubic symphysis are also manually palpated as being elevated compared to the other side. Pelvic obliquity has been found to be a common musculoskeletal evaluation finding in women with chronic pelvic pain including vulvodynia, persistent vulvar pain, and overactive pelvic floor muscles [58, 59].

It is common to find tight hip adductors and pelvic floor muscle tightness or tension on the side of the upslip. Pelvic obliquity can cause a chronic tension of the pelvic floor muscles, piriformis, quadratus lumborum, multifidus, iliolumbar ligament, and iliopsoas on the side that is elevated causing a stress–strain response. Continuous tension placed on the muscle results in strain and elevated resting tone. This leads to overactivity in the pelvic floor muscles and associated muscles in the region.

An upslip also puts stress–strain on the anterior and posterior sacroiliac ligaments, sacrotuberous ligament, and sacrospinous ligament. The pudendal nerve passes between the sacrotuberous and sacrospinous ligament, which is a common area of entrapment leading to pudendal neuralgia. Pudendal nerve irritation can cause overactive pelvic floor muscles. The pudendal and levator ani nerves can become tractioned, compressed, or irritated. Also, the sacral nerve roots that run anterior to the piriformis can become tractioned. Therefore, the irritated nerves can cause upregulation of the end organs such as the levator ani, genitalia, bladder, anus, and perineum.

Correction of pelvic obliquity via various manual physical therapy techniques has been studied and preliminary data suggests it improves low back pain [60] and would therefore likely also improve pelvic pain.

It has been found that pelvic floor muscle dysfunction can be a concomitant issue in patients with SIJD [25]. SIJD refers to pain in the sacroiliac region caused by pathomechanics from trauma, aberrant postures, degenerative arthritis, pregnancy, altered gait patterns, and inflammatory diseases such as gout, ankylosing spondylitis, and rheumatoid arthritis. SIJD can cause an inflammatory process at the joint and surrounding structures. Surrounding structures include the anterior and posterior sacroiliac ligaments, sacrotuberous, sacrospinous, and iliolumbar ligaments. Sacroiliac pain is felt near the joints and can occur between the medial aspect of the posterior iliac crest and gluteal sulcus. Referral of pain from SIJD can occur across the iliac crest laterally, into the buttock, pelvic floor muscles, and down the lateral and posterior thigh. Sacroiliac dysfunction with hypomobility or compression at the joint seems to be more related to overactive pelvic floor muscle dysfunction. Myofascially compressed sacroiliac joint findings include poor motor control, impaired patterns for lumbopelvic stabilization, posteriorly tilted pelvis, hip restrictions in flexion, adduction, and internal rotation motions, trigger points in the obturator internus, piriformis, and coccygeus tension [20]. Whereas, sacroiliac joint hypermobility or excess motion is related to pelvic floor muscle weakness. In order for the sacroiliac join to effectively transfer load, form closure and force closure ability of the joint has to be intact. The sacrotuberous and long dorsal ligaments have been the focus of research. Loading of the sacrotuberous ligament, which has connections with the gluteus maximus, long head of the biceps femoris, and sacrospinous ligament, restricts sacroiliac joint ventral rotation [15]. The long dorsal sacroiliac ligament is penetrated by S2–4 posterior sacral rami. When sacroiliac dysfunction exists a chronic inflammatory response occurs that can cause “wind up.” This physiologic “wind-up” phenomenon begins at the skin, affects the peripheral nerves, and results in a hypersensitivity response from the dorsal horn in the spinal cord and brain and can effect other structures along the same pathways such as the pudendal nerve, direct nerve branches S3–4, and pelvic floor muscles as one of the end organs.