The muscles of the hip are in some ways similar to the muscles of the shoulder. Numerous muscles induce movements of the legs and torso while using the bones in the hip area as an anchor. The ilium, sacrum, pubis, ischial, vertebrae, and other bones provide firm attachment points for muscles that move the largest limbs in the body.
The various hip and thigh fall muscles into four groups: the anterior group, posterior group, adductor group, and abductor group. These muscles are generally responsible for hip flexion, extension, adduction, and abduction, respectively. But individual muscles in each group also play other roles such as medial or lateral leg rotation.
Anterior Group MusclesThe anterior muscles include those muscles that cause the thigh to flex. If you raise your knee to deliver a Hiza Geri then you are using muscles in the anterior group. This group is further divided into the iliopsoas group and the quadriceps femoris group.
The iliopsoas group consists of two large muscles that eventually join to form the iliopsoas muscle. The two muscles involved are the psoas major and the iliacus.
The psoas major muscle originates from the transverse processes of the last thoracic vertebrae and lumbar vertebrae 1-4. It then passes inferiorly near the medial surfaces of the iliac where it eventually joins with the iliacus.
The iliacus originates from the iliac fossa on the medial side of the iliac and along the anterior superior spine of ilium (commonly called the anterior inferior iliac spine – AIIS). It then proceeds inferiorly until it joins the psoas major to form the iliopsoas. The iliopsoas inserts into the femur at the lesser trochanter just below the iliofemoral ligament.The psoas major forms a critical link between the axial and appendicular skeleton. It helps to flex the femur and contributes to lateral rotation of the femur and weakly contributes to hip adduction. The muscle also plays a major role in movements of the trunk of the body. When the psoas muscle on both sides of the body contract in unison the trunk of the body pulls forward (anteriorly). This is the muscle action that occurs when you initiate a sit-up. If the psoas muscle on only one side of the body contracts then the torso will bend laterally on that side of the body.
The iliacus has similar functionality. It too helps flex the femur. In addition it can cause the hips to rotate forward, but it does not affect the vertebral column directly. It is only involved in hip flexion.
So these two muscles work in conjunction to perform two essential functions. If the trunk of the body is held in a fixed position then contracting these muscles will cause flexing of the femur. If the legs are held in a fixed position, then contracting these muscles will cause hip and spinal flexion about the hip-joint.
Quadriceps Femoris Group
This muscle group consists of the rectus femoris, vastus intermedius, vastus lateralis, and vastus medialis muscles.
The rectus femoris (rectus is Latin for straight) has two points of origin. The first is on the inferior edge of the AIIS. The second is just superior to the acetabulum (the hip socket where the head of the femur rests). The opposite end of the muscle helps form the common quadriceps tendon. This tendon inserts at the patella. The tendon continues until it inserts via the patellar tendon at the tubercle of tibia.
The rectus femoris supports hip flexion and knee extension, but it has a limited range of effectiveness. It can help raise the femur (flex the hip-joint) until the femur is roughly at 90° to the torso. Following that the muscle is too shortened to provide additional contraction. The same occurs with knee extension. If the hip flexes the rectus femoris shortens. In this shortened state the muscle only provides limited support for extension of the knee.The vastus intermedius muscle sits deep to the rectus femoris. The vastus intermedius originates along the anterior and lateral surfaces of the femur. It inserts, along with the other muscles in this group, into the common quadriceps tendon. It functions to extend the knee.
The vastus lateralis originates from several areas along the femur shaft. These include the greater trochanter, the linea aspera (along the posterior side of the humerus), along the intertrochanteric line (where the iliofemoral ligament connects to the femur) and the gluteal tuberosity. It is the largest of the muscles in the quadriceps femoris group. The upper three-quarters of the muscle forms an aponeurosis that then connects to the various points of origin.
The vastus lateralis inserts at the common quadriceps tendon and provides much of the power for knee extensions.
The vastus medialis muscle, as you might suspect, is found on the medial surface of the thigh. It originates along a long continual line of anterior medial attachment beginning at the intertrochanteric line. This attachment continues along the entire length of the femur, moving posteriorly as it descends distally. It inserts via the common quadriceps tendon into the base of the patella and functions to provide flexion of the knee.
Additional Anterior Muscles
An additional muscle found in the anterior compartment of the thigh is the sartorius muscle. The sartorius, a long thin strap muscle, is the longest muscle in the human body. It originates at the head of the AIIS and the wraps around the anterior then medial sides of the thigh as it descends. It eventually passes posteriorly to the medial condyle of the femur and inserts via a tendon on the anterior medial surface of the tibia.
The sartorius muscle is a relatively weak muscle but does aid in hip flexion. It also helps to flex the knee and provides some support for hip abduction. Where the muscle is most involved is when you raise your foot and place it adjacent to the knee of the opposite leg. This requires both hip flexion and knee flexion that is provided in large part by the sartorius muscle. This muscle helps with Ippon Dachi and with simply crossing your legs to sit.
Posterior Group MusclesThe posterior muscle group consists of muscles that move the thigh in extension. The muscles in this group include those in both the gluteus group and the hamstrings group.
The muscles in the gluteus group include the gluteus maximus, gluteus medius, gluteus minimus, and tensor fasciae latae muscles.
The gluteus maximus is the largest muscle in the human body. It is so large that most diagrams depicting its location show it as cut or dissected so it is possible to see the muscles that lay deep to the gluteus maximus.
Because this muscle is so large it originates along a great many surface areas including along the crest of the ilium, the lower posterior portion of the sacrum, the lateral portion of the coccyx, the lumbodorsal fascia, the sacrotuberous ligament, and fascia covering the gluteus medius.
There are two insertions points for the gluteus maximus. The first is via a large tendon that passes over the great trochanter and inserts along the iliotibial band, a long fibrous band that reinforces and interconnects tissues in the thigh. The second insertion occurs below the great trochanter on the surface of the femur.
The gluteus maximus functions to extend the bent thigh when you wish to straighten your leg. But this same action can function to bring the bent torso back into an erect posture. The lower insertion point on the femur also functions to adduct and externally rotate of the femur.
The gluteus medius muscle originates on the posterior surface of the ilium just below the ilium crest and from the large connective tissue mass of the gluteal aponeurosis that permeates the region. The inferior portion of the muscle lies deep to the gluteus maximus. The gluteus medius inserts onto the lateral surface of the great trochanter. The muscle contains anterior and posterior sections which can function independently and often in opposition to one another. We will cover this more in a moment.
The gluteus medius has several functions. The first is stabilization of the hip-joint when lifting a leg off the ground. If you perform Ippon Dachi then the femur of the leg being held aloft pulls tightly into the pelvis to ensure the hip remains intact. This is a vital function during walking or running to ensure your hip does not become dislocated.
The anterior portion of the muscle also functions to support hip flexion and medial rotation of the femur. The posterior portion of the muscle functions to extend the hip and rotate the femur laterally. If both parts of the muscle operate simultaneously then the muscle functions to abduct the hip and stabilize and support the pelvis.
The gluteus minimus muscle originates on the inferior lateral surface of the posterior ilium. It lies deep to both the gluteus maximus and the gluteus medius. As the name implies the gluteus minimus is the smallest of the three gluteus muscles. It inserts onto the anterior surface of the great trochanter and functions in a manner similar to the gluteus medius.
The tensor fasciae latae muscle originates along the iliac crest and the anterior superior iliac spine. It connects to the common iliotibial band and ultimate inserts at the lateral condyle of the tibia. An essential function of this muscle is to provide stabilization of both the hip and knee joints when the leg is in various forms of flexion and extension. The muscle also is a hip abductor and supports medial rotation of the hip.
The hamstrings group consists of three posterior thigh muscles. These are the biceps femoris (depicted in red and purple at right), semimembranosus (blue), and semitendinosus (green) muscles.
The biceps femoris has two heads. The long head arises from the ischial tuberosity on the inferior portion of the ischium. The short head emerges from the linea aspera, a ridge along the middle third of the posterior portion of the femur. The two heads merge via connective tissues and finally insert via a tendon into the head of the fibula. A small portion of this tendon also inserts at the lateral condyle of the tibia.
Both heads of the biceps femoris produce knee flexion. The long head of the muscle also produces hip extension and provides lateral rotation of the leg.
The semitendinosus muscle arises from the same location as the long head of the biceps femoris. It inserts via a very long tendon into the anterior and medial surface of the tibia. The muscle works with the other two hamstring muscles to flex the knee and extend the hip. The semitendinosus muscle also provides support for medial rotation of the tibia and the femur (the latter after hip extension).
The semimembranosus muscle originates via a thick and wide tendon attached to the ischial tuberosity. The muscles inserts via a long tendon into the posterior aspect on the medial condyle of the tibia. Like the other hamstring muscles it functions to flex the knee and extend the hip. It also offers medial rotations similar to those provided by the semitendinosus muscle.
Adductor Group MusclesThere are several adductor muscles on the medial side of the thigh. These muscles function to pull the leg medially toward the center line. This group of muscles is commonly called the groin muscles and tearing or pulling one of these muscles is a common sport and martial arts injury.
The muscles in this group stretch between the hip and inner thigh. The muscles include the adductor longus, adductor brevis, adductor magnus, pectineus, and gracilis muscles. You use these muscles when performing any action that pulls a leg inward toward the other leg. They are also employed when you perform activities such as a Shovel Kick
The adductor longus muscle originates on the superior pubis ramus (superior ramus of pubis) and inserts along the middle third on the medial side of the femur. It functions, like other muscles in this group, to adduct the thigh, pulling a leg in toward the other leg. the adductor longus also supports lateral rotation of the thigh and provides weak support for thigh flexion.
The adductor brevis has narrow points of origin on the superior pubis ramus and inferior pubis ramus (inferior ramus of pubis). It lies deep to both the pectineus and adductor longus muscles and inserts on the femur along a line extending from below the lesser trochanter to the upper portion of the linea aspera. This insertion occurs via an aponeurosis rather than a dedicated tendon.
The largest of the adductor muscles is the adductor magnus. It consists of two different sections of muscle often called the oblique head and vertical head. The oblique head originates from the inferior portion of both the ischium and the pubis. The oblique head inserts along a line from the greater trochanter through the upper two-thirds of the linea aspera. This larger section of the muscle functions as part of the adductor group supporting adduction and flexion of the thigh. This portion of the muscle also supports lateral rotation of the femur.
The vertical head originates at the ischial tuberosity and inserts near the knee at the adductor tubercle of femur. Because of its position this head functions primarily as a part of the hamstring group rather than the adductor group. It supports hip extension and medial rotation of the leg when the leg is both flexed and rotated laterally.
The upper lateral part of the adductor magnus is often called the adductor minimus. It aids in adduction and lateral rotation of the thigh.
Arising along the superior ramus of the pubis, the pectineus muscle descends obliquely to insert along a posterior line between the lesser trochanter and the linea aspera of the femur. The muscle is primarily used for hip flexion but also plays a significant role in femur adduction.
The gracilis muscle originates along the inferior surfaces of the pubis. It is a long thin strap muscle that passes behind the medial condyle of the femur and inserts into the tibia at a location below the medial condyle of the tibia. Because of its origin and point of insertion the muscle plays many roles. It functions as an adductor of the thigh, but also medially rotates the hip, flexes the hip, and helps extend the lower leg.
Another muscle that is commonly grouped with the adductor muscles is the external obturator muscle (obturator externus). This muscle originates along the anterior surfaces of the pubis. It then traverses laterally and superiorly and inserts into the trochanteric fossa between the head and greater trochanter on the posterior of the femur. The muscle functions to both stabilize and provide lateral rotation of the hip-joint. While the obturator muscle does not provide adduction, it is often included in this group of muscles simply because of its general physical proximity to the other muscles of the adductor group.
Abductor Group Muscles
You will find the abductor muscles on the lateral side of the thigh. The abductor muscles function to pull the leg laterally away from the center line. Some of these muscles are also part of the posterior group muscles discussed earlier. The muscles we discussed earlier include the tensor fasciae latae, sartorius, gluteus medius, and gluteus minimus muscles. Most of these muscles support hip extension, but also play a role in hip abduction.
Additional muscles in the abductor group include the piriformis, superior gemellus, inferior gemellus and the obturator internus.
The piriformis muscle originates anterior lateral surfaces of the sacrum, the superior margin of the greater sciatic notch, and from various connective tissues near the sacrum. It inserts on the upper medial surface of the great trochanter of the femur. It functions both to abduct the hip-joint and cause lateral rotation of the femur. The muscle rotates the femur during hip extension and abducts the femur during hip flexion. If the hip flexes in excess of 90° then the piriformis muscle works to rotate the hip medially.
The superior and inferior gemellus muscles function to support lateral rotation of the extended femur. They also play an important role in stabilizing the femur insertion into the hip-joint (where the femur head rests in the acetabulum). The superior gemellus originates along the spine of the ischium. The inferior gemellus originates from the posterior ischial tuberosity. Both muscles then merge with the fibers of the obturator internus muscle, ultimately inserting on the medial surface of greater trochanter of femur.
The obturator internus originates from the anterior surface of the obturator membrane and from the posterior margins of the obturator foramen. Because it connects via the same tendon as the gemellus muscles it has similar functionality.