Anatomy, Bony Pelvis and Lower Limb, Femoral Muscles

Article Author:
Alyssa Ransom
Article Editor:
Shivajee Nallamothu
Updated:
9/19/2018 7:00:14 PM
PubMed Link:
Anatomy, Bony Pelvis and Lower Limb, Femoral Muscles

Introduction

The muscles of the femoral region of the lower limb are divided into three compartments. The anterior or extensor, medial or adductor and posterior or flexor compartments. Each compartment is separated from the others by intermuscular septa that run from the fascia lata to the linea aspera of the femur. The anterior compartment includes pectineus, iliopsoas, psoas minor, iliacus, sartorius and the quadriceps. These muscles arise from the hip, spine and proximal femur. The medial compartment is made up of the adductor magnus, adductor longus, adductor brevis, gracilis and obturator externus. These muscles originate near the anteroinferior external surface of the bony pelvis and insert at the linea aspera. The posterior compartment is made up of a group of muscles called the hamstrings, including semitendinosus, semimembranosus and biceps femoris.

Structure and Function

The three compartments of the femoral region each have a distinct function. The anterior or extensor compartment is responsible for flexion of the hip and extension of the knee. The posterior or flexor compartment are the prime extensors of the hip and flexors of the knee.  The medial or adductor compartment is composed of the adductors of the thigh.

Anterior Compartment 

Pectineus adducts, flexes, and assists in medial rotation of the thigh.

Iliopsoas made up of the psoas major and minor, and the iliacus come together to flex the hip joint as well as stabilize this joint during standing.

Sartorius helps the flex, abduct and laterally rotate the thigh at the hip joint. It also aids in the flexion of the knee joint, helping medial rotation of the leg in this position.

The quadriceps include four large muscles, rectus femoris, vastus lateralis, vastus medialis and vastus intermedius. This group of muscles has a common function. They extend the leg at the knee joint. Rectus femoris has an additional role in stabilizing the hip joint and aiding in the flexion of the thigh.

Posterior Compartment

The hamstrings a group of 3 muscles. 

Semitendinosus and semimembranosus extend the thigh, flex the leg and medially rotate the leg when the knee is flexed. These muscles also help to extend the trunk when both the thigh and leg are flexed.

Biceps femoris flexes the leg and when the knee is flexed rotates it laterally, and aids in the extension of the thigh.

Medial Compartment

Adductor longus is a major adductor of the thigh.

Adductor brevis aids in  adduction of the thigh and to a smaller extent flexes the thigh

Adductor magnus contains both an adductor part and a hamstring part each with their functions. The adductor part adducts and flexes the thigh. The hamstring part extends and adducts the thigh.

Gracilis is an adductor of the thigh, flexes the leg and aids in medial rotation of the leg.

Obturator externus is a lateral rotator of the thigh and is a major stabilizer of the head of the femur in the acetabulum.

Embryology

The Lower limb bud appears during the fifth week of development, growing laterally from the L2 through S2 segments. It contains each of the primary germ layers ectoderm, endoderm, and mesoderm. Lateral plate somatic mesoderm gives rise to skeletal elements, and the musculature arises from the myotomic portions of somites. The lower limb rotates 90 degrees medially along the longitudinal axis; this allows for the knee to face anteriorly. Apoptosis between the digits forms the digits.

Blood Supply and Lymphatics

The anterior compartment of the thigh receives blood from the femoral artery, which comes from the external iliac. It travels laterally to the femoral vein down the anterior thigh then passes to the back side of the thigh through the adductor hiatus. The deep artery of the thigh is the largest branch of the femoral artery. It dives deep and passes posterior to the adductor longus to supply muscles of all three compartments, the adductor magnus, hamstrings and vastus lateralis. The medial and lateral circumflex femoral arteries branch off the deep artery of the thigh and run around the head of the femur to supply the muscles in that area. The obturator artery splits into anterior and posterior branches and helps supply the adductor muscles.

The lymph from the leg travels to the superficial popliteal lymph nodes. The lymph vessels travel along with the femoral vessels to the deep inguinal lymph nodes. Lymph from the superficial tissues if the thigh drain to the superficial inguinal nodes. These drain to the external and common iliac the right and left lumbar lymph nodes. These then drain to the cisterna chyli and then the thoracic duct.

Nerves

The all of the anterior compartment of the thigh is innervated by the femoral nerve with the exception of the psoas major and minor, which are innervated by the anterior rami of the lumbar nerves (L1, L2, L3). The femoral nerve (L2, L3, L4) runs from the abdomen under the inguinal ligament to enter the later side of the femoral triangle. It is here that the nerve divides into the several branches. The Medial compartment of the thigh is innervated by the obturator nerve (L2, L3, L4). The only exception to this is the hamstring portion of the adductor magnus which is innervated by the tibial part of the sciatic nerve (L4). The Posterior compartment of the thigh is innervated by the sciatic nerve that is made up of a tibial and fibular division. Semitendinosus and semimembranosus are innervated by the tibial division (L5, S1, S2). Biceps femoris has dual innervation; the long head is innervated by the tibial nerve and the short head by the fibular division (L5, S1, S2). 

Muscles

Pectineus is a small square muscle that is found in the superomedial area of the thigh. Originating from the superior pubic ramus and inserting on the pectineal line of the femur, It is composed of two parts that each receive unique innervation, making this muscle transitional between the adductor and extensor compartments. 

The iliopsoas is made up of 3 muscles, the psoas major, psoas minor and the iliacus. The psoas major originates from sides and transverse processes of the T12 to L5 vertebrae. it passes down through the pelvis and under the inguinal ligament to insert of the lesser trochanter of the femur. The psoas minor originates from the sides of T12 through L1 vertebrae, sitting on top of the psoas major, then inserting on the pectineal line. The iliacus originates from the iliac crest, iliac fossa, ala of the sacrum and anterior sacroiliac ligaments. It joins the psoas muscles traveling deep to the inguinal ligament and inserting on the tendon of the psoas major and the distal part of the lesser trochanter of the femur. 

Sartorius is a long band-like muscle that runs lateral to medial crossing the anterior aspect of the thigh. It originates from the anterior superior iliac spine running superficially to the quadriceps muscles and inserting on the superomedial surface of the tibia. It is the longest muscle in the body, crossing 2 joints and helps in the completion of numerous actions.

The quadriceps femoris is one of the strongest muscle groups in the body that covers the anterior aspect of the femur. The group is made up of 4 muscles: rectus femoris, vastus lateralis, vastus intermedius and vastus medialis. Rectus femoris originates from the anterior inferior iliac spine. It is named for its course straight down the anterior part of the thigh. Vastus lateralis originates from the from the greater trochanter. The largest muscle in the quadriceps is found on the lateral aspect of the thigh. Vastus medialis originates from the intertrochanteric line and medial lip of the linea aspera of the femur. It covers the medial aspect of the femur.  Vastus intermedius originates from the anterior and lateral shaft of the femur. It can be found lying between the vastus lateral is and the vastus medialis just deep to the rectus femoris. All 4 muscles come together to form the quadriceps tendon which continues across the knee joint to become the patellar ligament that attaches to the tibial tuberosity.

The Hamstrings

Adductor longus is the most anterior muscle in the group. It fans out from its origin on the anterior aspect of the pubis and inserts on the linea aspera of the femur. It covers both the anterior portion of the adductor brevis and the central portion of the adductor magnus.

Adductor brevis is the smallest of the group, lying just deep to pectineus and adductor longus. It originates from the body and inferior ramus of the pubis spreading to inserting on the proximal portion of the linea aspera. This muscle divides the obturator nerve into an anterior and posterior division.

Adductor magnus is the largest of the adductor muscle. The most posterior of the adductor muscle, which crosses into the posterior compartment. Allowing this muscle to have both an adductor part and a hamstring part, separated by attachments, innervation, and actions. The adductor part originates from the inferior ramus of the pubis and the ramus of the ischium and inserts on the linea aspera and the medial supracondylar ridge. This portion of the muscle has an opening in the tendon allowing for the passage of important vessels to the posterior side of the knee. The hamstring portion originates from the ischial tuberosity and inserts of the adductor tubercle of the femur.

Gracilis the weakest and most medial of the adductor muscles. It can be recognized by its long a slender appearance. It crosses both the hip and the knee joint, originating from the body and inferior ramus of the pubis and inserts with two other muscles in the tendinous pes anserinus which attaches to the medial surface of the tibia. With the aid of the other two muscles in the common insertion are important stabilizers of the medial side of the extended knee.

Obturator externus is a small muscle found in the superomedial area of the thigh. Originating from the external surface of the obturator membrane and inserts on the posterior side of the greater trochanter. It passes distal to the neck of the femur and the acetabulum.

Clinical Significance

Understanding the anatomy of the femoral muscles is incredibly important for clinicians to determine a diagnosis for their patients. Muscle pain and weakness can also be signals of a nerve or vessel injury. 

The hamstrings are commonly strained in activities such as running or jumping; these injuries can be very painful.

Damage to the femoral nerve causes paralysis of the quadriceps, so there are significant deficits in the flexion of the hip and extension of the leg. In cases of obturator nerve damage the patient will present with weakness in adduction and a lateral swinging of the limb during walking there is a lack of opposition to the abductors. When the sciatic nerve is damaged, the extension of the hip and flexion of the knee are impaired, along with several deficits in the foot and ankle. This type of injury can easily be recognized by clinicians because the patient will increase the flexion of the hip to lift the dropped foot off of the ground.