The iliopsoas muscles (Fig. 8.10) might well be the most interesting muscles of the entire myofascial system. They are certainly the muscles whose functions are discussed with the most controversy. Because of their attachments and especially their course, they are able to adjust the position of the hip, pelvis, and LSC to each other.
For Basmajian, they are the most important muscles of the body for posture. They are able to adjust the spinal column and the pelvis in both the frontal and sagittal planes.
Lewit writes that the psoas often causes abdominal pain in the iliac fossa or imitates gall or renal colic.86 The psoas is directly involved in respiration due to its origination in T12 and the medial arcuate ligament of the diaphragm.
Bogduk14 states that a psoas spasm places enormous strain on the lumbar intervertebral disks. Fryette,56 Kuchera,82 Di Giovanni,49 and others describe the psoas syndrome as the main cause for acute lumbago.
The psoas is considered a postural muscle; that is. a muscle with type-l fibers. We do. in fact, commonly find shortened iliopsoas muscles, but just as frequently spasmodic ones. According to Lewit,86 a psoas contraction causes pain in the thoracolumbar junction (TCJ), and hypertonicity of the iliac causes pain in the ISJ.
Hypertonicity of the psoas can cause nerve irritations in the lumbar plexus. The psoas originates in the vertebral bodies T12-L4 (L5) and the intervertebral disks in between, as well as in the transverse processes of L1-L4. The lumbar plexus passes between the bellies of the two muscles. The iliac muscle has its origin in the iliac fossa.
Both muscles unite and run below the inguinal ligament to the lesser trochanter of the femur. The psoas minor originates at the belly of the psoas major and has a caudal attachment at the crista pectinea and the inguinal ligament.
The iliopsoas is enveloped by taut fascia, namely the iliac fascia. This is a caudal extension of the diaphragm fascia. The iliac fascia is connected at the pelvis with the inguinal ligament.
The muscle serves as slide rail for the kidney and is also in contact with the other organs. Its course is from dorsal-medial-cranial to caudal-ventral-lateral. At the level of the crista pectinea, the fibers change direction and run towards dorsal-lateral.
The muscle passes in front of the hip joint, from which it is separated by a bursa. This reversal in the direction of the fibers at the pubic ramus has the effect that the muscle turns the ilium ventrally when tensed. The psoas thereby supports the pull of the iliac.
• Both iliopsoas muscles are the strongest hip flexors in the body. With the legs stabilized, they turn the iliac wings forward and thereby create an antever-sion of the pelvis. They are flexors of the lumbar vertebrae when the pelvis is prevented from tipping forward.
• They are ipsilateral side benders of the LSC. If the spinal column is able to form a lordosis at this point (is in "easy flexion" according to Fryette), the vertebrae turn into the convexity. If the pelvis is unable to tip forward (tension of the abdominal muscles or the pelvic floor), the psoas with the LSC make a flexion, sidebending, and ipsilateral rotation.
Lumbar segments LI, L2 (L3) ■ Hip Rotators
The muscle group of the hip rotators (Fig. 8.11) is formed by the piriformis, gemelli, obturator internus, and obturator externus. These are all muscles close to the joint, whose lever arm is too short to carry out strong movements. Therefore they have more of a proprioceptive function for the hip joint. They adapt the rotation of the femur to that of the ilium, with the goal of centering the head
of the hip optimally into the hip joint socket. In conjunction with the pelvic floor muscles, they form a sort of hammock for the pelvis.
In the stance stage of the gait and in one-legged stance, the piriformis and gluteus maximus stabilize the diagonal axis of the sacrum. The piriformis is a postural muscle that tends to shortening. It leaves the pelvis through the greater ischiadic notch. Here it is in close connection with the gluteal nerves, the pudendal nerve, the ischiadic nerve, as well as the vessels that supply the pelvic floor. Contraction of the piriformis can irritate these structures and cause pseudo-neuralgias or disturbances in perineal function. The leg is then rotated outward and shortened. The pain radiates outward to the ISJ, the buttocks, and the backside of the thigh. In rare cases, the pain extends more deeply into the back of the knee. Longer sitting or squatting with knees pressed together causes pain because the piriformis is stretched (in the case of a piriformis lesion).
As already mentioned, hip rotators have a proprioceptive function for the hip joint. They are outward rotators for the hip and abductors, as well as light extensors. In hip flexions of over 60", the piriformis serves as inward rotator of the hip.
We could continue this list of interesting muscles and muscle groups at will, but want to leave it at this. However, before concluding this chapter, we want to say a few words about the ventral muscles:
• The muscles of the hyoid bone play an absolutely minor role as mobilizers of the CSC. They are mainly active in movements of the lower jaw (mouth opener), whereby the lower muscles stabilize the hyoid bone. They play a role in swallowing, yawning, speaking, and breathing.
Their main function lies most likely in preventing the collapse of the trachea and gullet during head and neck movements.
To function as head flexor, the mouth has to be closed by the muscles of mastication. It is primarily the prevertebral muscles and the SCM that function as flexors of the CSC (when the head is flexed).
• The intercostal muscles stabilize the trunk and contribute to trunk rotations. In this aspect, they are synergists of the oblique abdominal muscles. Their main function, however, lies in assisting the respiratory muscles. This characteristic also holds true while they carry out support functions.
The abdominal muscles, especially the rectus abdominis, are antagonists of the longissimus thoracis, a fact that emphasizes their affiliation with the thoracic muscles.
They are active in almost all movements of the trunk and lower extremities. Herein, they act less as mobi-lizer than as stabilizer of the trunk, by compressing the abdominal organs and the thorax, which supports the spinal column.
The abdominal muscles and the lumbar multifidi muscles are active in gait before the muscles of the lower extremities (the transversus abdominis is the first).
With the exception of the hip rotators, all other muscles we have introduced (SCM, scalene, diaphragm, and iliopsoas) have the option to support other muscles in flexion as well as extension of the spinal column:
• The SCM extends the upper CSC and flexes it when the lower CSC is in flexion.
• The scalene muscles are benders of the CSC. When the paravertebral muscles in the neck make the CSC lordotic, the scalene muscles change their function to support the paravertebral muscles.
• The diaphragm can flex or extend the TCJ, depending on need.
• The iliopsoas can assist in making the LSC lordotic or extending it.
When the abdominal muscles and pelvic floor retro-verse the pelvis, the psoas makes the LSC kyphotic. The hip rotators are muscles whose significance is underestimated. During walking, the weight shifts from the sagittal to the frontal plane. Movement in the pelvis changes from a flexion-extension of the spinal column into an abduction-adduction (to maintain equilibrium). The hip rotators assist in stabilizing the pelvis and guarantee a good congruence of the hip ball in the joint socket. As a result, these muscles are frequently overloaded in all pelvic dysfunctions.
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