The iliopsoas muscle (; from lat, ile, lit=groin and grc, ψόᾱ, psóā, muscles of the loins) refers to the joined
psoas major
The psoas major ( or ; from grc, ψόᾱ, psóā, muscles of the loins) is a long fusiform muscle located in the lateral lumbar region between the vertebral column and the brim of the lesser pelvis. It joins the iliacus muscle to form the iliop ...
and the
iliacus muscle
The iliacus is a flat, triangular muscle which fills the iliac fossa. It forms the lateral portion of iliopsoas, providing flexion of the thigh and lower limb at the acetabulofemoral joint.
Structure
The iliacus arises from the iliac fossa on t ...
s. The two muscles are separate in the
abdomen
The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. ...
, but usually merge in the
thigh
In human anatomy, the thigh is the area between the hip (pelvis) and the knee. Anatomically, it is part of the lower limb.
The single bone in the thigh is called the femur. This bone is very thick and strong (due to the high proportion of bone ...
. They are usually given the common name ''iliopsoas''. The iliopsoas muscle joins to the
femur
The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...
at the
lesser trochanter
The lesser trochanter is a conical posteromedial bony projection of the femoral shaft. it serves as the principal insertion site of the iliopsoas muscle.
Structure
The lesser trochanter is a conical posteromedial projection of the shaft of the fe ...
. It acts as the strongest
flexor
A flexor is a muscle that flexes a joint. In anatomy, flexion (from the Latin verb ''flectere'', to bend) is a joint movement that decreases the angle between the bones that converge at the joint. For example, one’s elbow joint flexes when one ...
of the hip.
The iliopsoas muscle is supplied by the lumbar spinal nerves
L1–
L3 (psoas) and parts of the
femoral nerve
The femoral nerve is a nerve in the thigh that supplies skin on the upper thigh and inner leg, and the muscles that extend the knee.
Structure
The femoral nerve is the major nerve supplying the anterior compartment of the thigh. It is the largest ...
(iliacus).
Structure
The iliopsoas muscle is a
composite muscle
Composite or hybrid muscles are those muscles which have more than one set of fibers but perform the same function and are usually supplied by different nerves for different set of fibers.
Examples
* Brachialis: Musculocutaneous nerve is motor an ...
formed from the psoas major muscle, and the iliacus muscle. The psoas major originates along the outer surfaces of the
vertebral bodies
The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...
of
T12 and
L1–
L3 and their associated
intervertebral discs
An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column. Each disc forms a fibrocartilaginous joint (a symphysis), to allow slight movement of the vertebrae, to act as a ligament to hold t ...
.
The iliacus originates in the
iliac fossa
The iliac fossa is a large, smooth, concave surface on the internal surface of the Ilium (bone), ilium (part of the three fused bones making the hip bone).
Structure
The iliac fossa is bounded above by the iliac crest, and below by the Arcuate l ...
of the
pelvis
The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton).
The ...
.
The psoas major unites with the iliacus at the level of the
inguinal ligament
The inguinal ligament (), also known as Poupart's ligament or groin ligament, is a band running from the pubic tubercle to the anterior superior iliac spine. It forms the base of the inguinal canal through which an indirect inguinal hernia may dev ...
. It crosses the hip joint to insert on the
lesser trochanter
The lesser trochanter is a conical posteromedial bony projection of the femoral shaft. it serves as the principal insertion site of the iliopsoas muscle.
Structure
The lesser trochanter is a conical posteromedial projection of the shaft of the fe ...
of the
femur
The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...
.
The iliopsoas is classified as an "anterior hip muscle" or "inner hip muscle".
The
psoas minor
The psoas minor muscle ( or ; from grc, ψόᾱ, psóā, muscles of the loins) is a long, slender skeletal muscle. When present, it is located anterior to the psoas major muscle.Tank (2005), p 93Gray (2008), p 1372
Structure
The psoas minor mu ...
does contribute to the iliopsoas muscle.
The inferior portion below the inguinal ligament forms part of the floor of the
femoral triangle
The femoral triangle (or Scarpa's triangle) is an anatomical region of the upper third of the thigh. It is a subfascial space which appears as a triangular depression below the inguinal ligament when the thigh is flexed, abducted and laterally rot ...
.
Nerve supply
The psoas major is innervated by direct branches of the anterior rami of the
lumbar plexus
The lumbar plexus is a web of nerves (a nervous plexus) in the lumbar region of the body which forms part of the larger lumbosacral plexus. It is formed by the Ventral ramus of spinal nerve, divisions of the first four lumbar nerves (L1-L4) and ...
at the levels of L1–L3, while the iliacus is innervated by the
femoral nerve
The femoral nerve is a nerve in the thigh that supplies skin on the upper thigh and inner leg, and the muscles that extend the knee.
Structure
The femoral nerve is the major nerve supplying the anterior compartment of the thigh. It is the largest ...
(which is composed of nerves from the
anterior rami
The ventral ramus (pl. ''rami'') (Latin for ''branch'') is the anterior division of a spinal nerve. The ventral rami supply the antero-lateral parts of the trunk (anatomy), trunk and the limbs. They are mainly larger than the dorsal ramus of spinal ...
of
L2–
L4).
Function
The iliopsoas is the prime mover of hip flexion, and is the strongest of the
hip flexors
A flexor is a muscle that flexes a joint. In anatomy, flexion (from the Latin verb ''flectere'', to bend) is a joint movement that decreases the angle between the bones that converge at the joint. For example, one’s elbow joint flexes when one ...
(others are
rectus femoris
The rectus femoris muscle is one of the four quadriceps muscles of the human body. The others are the vastus medialis, the vastus intermedius (deep to the rectus femoris), and the vastus lateralis. All four parts of the quadriceps muscle attach to ...
,
sartorius, and
tensor fasciae latae
The tensor fasciae latae (or tensor fasciæ latæ or, formerly, tensor vaginae femoris) is a muscle of the thigh. Together with the gluteus maximus, it acts on the iliotibial band and is continuous with the iliotibial tract, which attaches to the ...
). The iliopsoas is important for
standing
Standing, also referred to as orthostasis, is a position in which the body is held in an ''erect'' ("orthostatic") position and supported only by the feet. Although seemingly static, the body rocks slightly back and forth from the ankle in the s ...
,
walking
Walking (also known as ambulation) is one of the main gaits of terrestrial locomotion among legged animals. Walking is typically slower than running and other gaits. Walking is defined by an 'inverted pendulum' gait in which the body vaults o ...
, and
running
Running is a method of terrestrial locomotion allowing humans and other animals to move rapidly on foot. Running is a type of gait characterized by an aerial phase in which all feet are above the ground (though there are exceptions). This is ...
.
The iliacus and psoas major perform different actions when postural changes occur.
The iliopsoas muscle is covered by the
iliac fascia
The iliac fascia, or Abernethy's fascia, is a fascia in the region of the ilium of the pelvis.
It has the following connections:
* ''laterally'', to the whole length of the inner lip of the iliac crest.
* ''medially'', to the linea terminalis of ...
, which begins as a strong tube-shaped psoas fascia, which surround the psoas major muscle as it passes under the
medial arcuate ligament
The medial arcuate ligament (also medial lumbocostal arch and internal arcuate ligament) is a tendinous fascia that arches over the psoas major muscle as it passes posterior the diaphragm.
Structure
The medial arcuate ligament is an arch in the f ...
. Together with the
iliac fascia
The iliac fascia, or Abernethy's fascia, is a fascia in the region of the ilium of the pelvis.
It has the following connections:
* ''laterally'', to the whole length of the inner lip of the iliac crest.
* ''medially'', to the linea terminalis of ...
, it continues down to the
inguinal ligament
The inguinal ligament (), also known as Poupart's ligament or groin ligament, is a band running from the pubic tubercle to the anterior superior iliac spine. It forms the base of the inguinal canal through which an indirect inguinal hernia may dev ...
where it forms the
iliopectineal arch
The Iliopectineal arch is a thickened band of fused iliac fascia and psoas fascia passing from the posterior aspect of the inguinal ligament anteriorly across the front of the femoral nerve to attach to the iliopubic eminence of the hip bone pos ...
which separates the
muscular
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscle ...
and
vascular lacuna
The vascular lacuna (Latin: ''lacuna vasorum'') is the compartment beneath the inguinal ligament which allows for passage of the femoral vessels, lymph vessels and lymph nodes. Its boundaries are the iliopectineal arch, the inguinal ligament, ...
e.
Clinical significance
It is a typical posture muscle dominated by
slow-twitch red type 1 fibers. Since it originates from the lumbar vertebrae and discs and then inserts onto the femur, any structure from the lumbar spine to the femur can be affected directly. A short and tight iliopsoas often presents as externally rotated legs and feet. It can cause pain in the low or mid back,
SI joint
The sacroiliac joint or SI joint (SIJ) is the joint between the sacrum and the ilium bones of the pelvis, which are connected by strong ligaments. In humans, the sacrum supports the spine and is supported in turn by an ilium on each side. Th ...
, hip, groin, thigh, knee, or any combination. The iliopsoas gets innervation from the L2-4 nerve roots of the
lumbar plexus
The lumbar plexus is a web of nerves (a nervous plexus) in the lumbar region of the body which forms part of the larger lumbosacral plexus. It is formed by the Ventral ramus of spinal nerve, divisions of the first four lumbar nerves (L1-L4) and ...
which also send branches to the superficial lumbar muscles. The
femoral nerve
The femoral nerve is a nerve in the thigh that supplies skin on the upper thigh and inner leg, and the muscles that extend the knee.
Structure
The femoral nerve is the major nerve supplying the anterior compartment of the thigh. It is the largest ...
passes through the muscle and innervates the
quadriceps
The quadriceps femoris muscle (, also called the quadriceps extensor, quadriceps or quads) is a large muscle group that includes the four prevailing muscles on the front of the thigh. It is the sole extensor muscle of the knee, forming a large ...
,
pectineus, and
sartorius muscle
The sartorius muscle () is the longest muscle in the human body. It is a long, thin, superficial muscle that runs down the length of the thigh in the Anterior compartment of thigh, anterior compartment.
Structure
The sartorius muscle originates f ...
s. It also comprises the intermediate femoral cutaneous and medial femoral cutaneous nerves which are responsible for sensation over the anterior and medial aspects of the thigh, medial shin, and arch of the foot nerves. The
obturator nerve
The obturator nerve in human anatomy arises from the ventral divisions of the second, third, and fourth lumbar nerves in the lumbar plexus; the branch from the third is the largest, while that from the second is often very small.
Structure
The o ...
also passes through the muscle which is responsible for the sensory innervation of the skin of the medial aspect of the thigh and motor innervation of the adductor muscles of the lower extremity (
external obturator
The external obturator muscle, obturator externus muscle (; OE) is a flat, triangular muscle, which covers the outer surface of the anterior wall of the pelvis.
It is sometimes considered part of the medial compartment of thigh, and sometimes ...
,
adductor longus
In the human body, the adductor longus is a skeletal muscle located in the thigh. One of the adductor muscles of the hip, its main function is to adduct the thigh and it is innervated by the obturator nerve. It forms the medial wall of the fem ...
,
adductor brevis
The adductor brevis is a muscle in the thigh situated immediately deep to the pectineus and adductor longus. It belongs to the adductor muscle group. The main function of the adductor brevis is to pull the thigh medially. The adductor brevis ...
,
adductor magnus Adductor may refer to:
* One of the anatomical terms of motion
* Adductor muscle (disambiguation)
* Adductor canal
The adductor canal, also known as the subsartorial canal or Hunter’s canal, is an aponeurotic tunnel in the middle third of the th ...
,
gracilis) and sometimes the
pectineus. Any of these innervated structures can be affected.
Bleeding
Iliopsoas muscle is a common site of
bleeding
Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, vag ...
in patients who are undergoing blood
anticoagulation
Anticoagulants, commonly known as blood thinners, are chemical substances that prevent or reduce coagulation of blood, prolonging the clotting time. Some of them occur naturally in blood-eating animals such as leeches and mosquitoes, where the ...
.
Additional images
File:Slide20LLLL.JPG, Iliopsoas muscle
See also
*
Psoas abscess
An abscess in the psoas muscle of the abdomen may be caused by lumbar tuberculosis. Owing to the proximal attachments of the iliopsoas, such an abscess may drain inferiorly into the upper medial thigh and present as a swelling in the region. T ...
*
Iliopsoas tendonitis
*
Muscles of the hip
In human anatomy, the muscles of the hip joint are those muscles that cause movement in the hip. Most modern anatomists define 17 of these muscles, although some additional muscles may sometimes be considered. These are often divided into fou ...
*
Dr. Ronald Conger
References
External links
*
{{Authority control
Hip flexors
Iliopsoas muscles
Muscles of the lower limb