Fascia and Muscles of the Front of the Thigh

Introduction

• The front of the thigh extends from the hip to the knee and contains the fascia and anterior thigh muscles, which play essential roles in hip flexion, knee extension, posture, and locomotion.

Surface Landmarks

1. The anterior superior iliac spine (ASIS) is a prominent bony projection at the anterior end of the iliac crest.
2. The iliac tubercle is a bony prominence located on the outer lip of the iliac crest, approximately 5 cm behind the ASIS.
3. The groin fold is a shallow curved groove extending from the ASIS to the pubic tubercle. It overlies the inguinal ligament and is convex downward due to the pull of the deep fascia of the thigh.
4. The pubic tubercle is a palpable bony prominence at the medial end of the groin fold.
5. The pubic crest is a short bony ridge situated between the pubic tubercle and the pubic symphysis.
6. The greater trochanter of the femur can be palpated approximately a hand’s breadth below the iliac tubercle.
7. The midpoint of the inguinal ligament lies midway between the ASIS and the pubic tubercle.
8. The midinguinal point, located midway between the ASIS and the pubic symphysis, is an important clinical reference point.
9. The patella (kneecap) is the largest sesamoid bone, embedded within the quadriceps femoris tendon, and is easily visible and palpable on the front of the knee.
10. The tibial tuberosity is a prominent bony elevation below the patella and continues inferiorly as the anterior border (shin) of the tibia.
11. The medial and lateral femoral condyles and the tibial condyles form the palpable bony prominences on either side of the knee. The most projecting parts of the femoral condyles are the medial and lateral epicondyles.
12. The adductor tubercle is a small bony projection located just above the medial condyle of the femur.

Superficial Fascia

• The superficial fascia consists of two layers only in the upper part of the thigh:
  • Superficial fatty layer
  • Deep membranous layer

• These layers are continuous with the corresponding layers of the superficial fascia of the anterior abdominal wall.
• The deep membranous layer is firmly attached to the deep fascia along the Holden’s line.
• Holden’s line extends horizontally for about 8 cm, beginning just lateral to the pubic tubercle. The attachment along Holden’s line prevents extravasated urine from passing into the thigh following rupture of the urethra in the perineum, making it an important clinical landmark.

Contents of Superficial Fascia

The superficial fascia contains the following structures:

1. Cutaneous nerves
2. Cutaneous arteries
3. Superficial veins, including the termination of the great saphenous vein and its tributaries
4. Superficial inguinal lymph nodes

Cutaneous Innervations of Front of Thigh

• The skin of the anterior thigh receives sensory innervation from seven nerves. These nerves are:
  1. Ilioinguinal nerve
  2. Femoral branch of the genitofemoral nerve
  3. Lateral cutaneous nerve of the thigh
  4. Intermediate cutaneous nerve of the thigh
  5. Medial cutaneous nerve of the thigh
  6. Saphenous nerve
  7. Cutaneous branch of the obturator nerve

Key Description

Ilioinguinal Nerve (L1)

• The ilioinguinal nerve is a branch of the first lumbar nerve (L1). It accompanies the spermatic cord in males and the round ligament of the uterus in females through the inguinal canal. It emerges through the superficial inguinal ring, located just medial to the pubic tubercle.
• Distribution:
  1. Supplies the upper medial part of the thigh.
  2. Gives the anterior scrotal nerves in males.
  3. Gives the anterior labial nerves in females.

Femoral Branch of the Genitofemoral Nerve (L1, L2)

• The genitofemoral nerve arises from the lumbar plexus and divides into genital and femoral branches. The femoral branch pierces the femoral sheath and deep fascia about 2 cm below the midinguinal point.
• Distribution: Supplies the skin over the femoral triangle.

Lateral Cutaneous Nerve of the Thigh (L2, L3)

• This nerve arises from the lumbar plexus. It enters the thigh by passing deep to the inguinal ligament, just medial to the ASIS.
• Distribution:
  • Divides into anterior and posterior branches.
  • Supplies the anterolateral thigh and the anterior part of the gluteal region.

Intermediate Cutaneous Nerve of the Thigh (L2, L3)

• It is a branch of the anterior division of the femoral nerve. It pierces the deep fascia at the junction of the upper and middle thirds of the thigh.
• Distribution: Divides into several branches that supply the skin of the anterior thigh.

Medial Cutaneous Nerve of the Thigh (L2, L3)

• It arises from the anterior division of the femoral nerve. It divides into anterior and posterior branches. The anterior branch pierces the deep fascia in the lower third of the thigh and supplies the lower medial thigh. The posterior branch pierces the fascia along the medial border of the sartorius and supplies the medial thigh.

Saphenous Nerve (L3, L4)

• The saphenous nerve is the largest cutaneous branch of the femoral nerve. It pierces the deep fascia on the medial side of the knee and descends with the great saphenous vein. It gives an infrapatellar branch, which supplies the skin over the patellar ligament.

Cutaneous Branch of the Obturator Nerve (L2, L3)

• This small branch arises from the anterior division of the obturator nerve.
• Distribution: Supplies the lower one-third of the medial thigh.

Patellar Plexus

• The patellar plexus is a network of fine cutaneous nerves located anterior to the patella. It supplies the skin over the front of the knee.
• It is formed by branches of:
  1. Anterior branch of the lateral cutaneous nerve of the thigh
  2. Intermediate cutaneous nerve of the thigh
  3. Anterior branch of the medial cutaneous nerve of the thigh
  4. Infrapatellar branch of the saphenous nerve

Cutaneous Vessels

Superficial Arteries

• The superficial fascia over the femoral triangle contains three cutaneous branches of the femoral artery:
  • Superficial external pudendal artery
  • Superficial epigastric artery
  • Superficial circumflex iliac artery

1. Superficial External Pudendal Artery: It arises from the femoral artery. It pierces the cribriform fascia and runs medially across the spermatic cord. Distribution: Supplies the external genitalia.
2. Superficial Epigastric Artery: It is a branch of the femoral artery. It pierces the cribriform fascia and ascends toward the umbilicus. Distribution: Supplies the lower part of the anterior abdominal wall.
3. Superficial Circumflex Iliac Artery: It is the smallest cutaneous branch of the femoral artery. It pierces the cribriform fascia and runs laterally, parallel to the inguinal ligament. It passes through the femoral sheath and fascia lata lateral to the saphenous opening.

Great saphenous vein

• The great saphenous vein (long saphenous vein) is the longest vein in the body.
• Origin: Begins at the medial end of the dorsal venous arch on the dorsum of the foot.
• Course: Ascends along the medial side of the leg, passes behind the knee, then runs upward and forward in the thigh to the femoral triangle. It pierces the cribriform fascia before terminating.
• Termination: Drains into the femoral vein.

Tributaries

• In the thigh:

• Anterolateral vein of the thigh
• Posteromedial vein of the thigh
• Before piercing the cribriform fascia:

• Superficial epigastric vein
• Superficial circumflex iliac vein
• Superficial external pudendal vein
• Just before joining the femoral vein:
• Deep external pudendal vein

Inguinal Lymph Nodes

• The inguinal lymph nodes are divided into two groups:

• Superficial inguinal lymph nodes
• Deep inguinal lymph nodes

Superficial inguinal lymph nodes

• These nodes lie in the superficial fascia over the femoral triangle.
• They are arranged in a T-shaped pattern and are divided into three groups.

Lower Vertical Group

• Consists of 4–5 lymph nodes located along the terminal part of the great saphenous vein.
• Drainage:
  • Skin and superficial fascia of the lower limb, except the buttock
  • Region drained by the short saphenous vein

Upper Lateral Group

• Consists of 2–3 lymph nodes situated below the lateral part of the inguinal ligament.
• Drainage:
  • Lateral infraumbilical anterior abdominal wall
  • Buttock
  • Flank and back below the umbilical plane

Upper Medial Group

• Consists of 2–3 lymph nodes located below the medial end of the inguinal ligament.
• Drainage:
  • Medial infraumbilical anterior abdominal wall
  • Perineum and external genitalia, except the glans penis and glans clitoris
  • Anal canal below the pectinate line
  • Penile urethra
  • Lower vagina (below the hymen)
  • Superolateral angle of the uterus via the round ligament

Deep inguinal nodes

• The deep inguinal nodes are 4–5 lymph nodes located medial to the upper part of the femoral vein within the femoral triangle.
• Their efferent vessels drain into the external iliac lymph nodes.

Cloquet’s (Rosenmüller’s) Node

• Cloquet’s node is the highest deep inguinal lymph node, located in the femoral canal.
• Drainage:
  • Superficial inguinal lymph nodes
  • Popliteal lymph nodes
  • Glans penis and glans clitoris
  • Deep lymphatics of the lower limb accompanying the femoral vessels

Deep Fascia of Thigh (Fascia Lata)

• The fascia lata is the deep fascia of the thigh, forming a strong fibrous sheath that encloses the thigh like a sleeve.

Attachments

Superior Attachments

• The fascia lata is attached to the inguinal ligament, iliac crest, gluteal fascia, pubis, pubic arch, and ischial spine.
• Through the gluteal fascia, it is also connected to the sacrum, coccyx, and sacrotuberous ligament.

Inferior Attachments

• Inferiorly, it is attached to the front and sides of the knee, the subcutaneous bony prominences, and the capsule of the knee joint.

Iliotibial tract

• The iliotibial tract (IT tract) is a thickened lateral part of the fascia lata, also known as the Maissiat band.
• It is approximately 5 cm wide.

Attachments

• Superiorly, it divides into:
  • Superficial lamina, attached to the iliac tubercle
  • Deep lamina, attached to the capsule of the hip joint
• Inferiorly, it is attached to the anterior surface of the lateral condyle of the tibia.

Muscle Attachments

• The upper part of the iliotibial tract receives the insertion of:
  • Tensor fasciae latae
  • Superficial three-fourths of the gluteus maximus

Functions

• The iliotibial tract provides lateral stability to the knee joint during extension and partial flexion, especially during walking and running.
• It helps support the body against gravity when standing with the knee slightly flexed, preventing the trunk from falling forward.

Saphenous Opening

• The saphenous opening is an oval opening in the fascia lata. It is located approximately 4 cm below and lateral to the pubic tubercle. The opening measures about 2.5 cm in length and 2 cm in width, with its long axis directed downward and laterally.

Margins

• The inferolateral margin is sharp and crescent-shaped, forming the falciform margin. The medial margin is ill-defined and deeper.

Closure

• The opening is closed by the cribriform fascia, a specialized part of the superficial fascia of the thigh.

Structures Passing Through the Saphenous Opening

1. Great saphenous vein
2. Superficial epigastric vessels
3. Superficial external pudendal vessels
4. Lymphatic vessels passing from the superficial to the deep inguinal lymph nodes

Fascial Compartments of Thigh

• The deep fascia (fascia lata) forms a strong fibrous sleeve that encloses the structures of the thigh.
• Three intermuscular septa extend from the fascia lata to the linea aspera of the femur:
  1. Medial intermuscular septum
  2. Lateral intermuscular septum
  3. Posterior intermuscular septum
• These septa divide the thigh into three fascial compartments.
  1. Anterior Compartment: Located between the medial and lateral intermuscular septa. Contains the extensor muscles of the thigh.
  2. Medial Compartment: Located between the medial and posterior intermuscular septa. Contains the adductor muscles of the thigh.
  3. Posterior Compartment: Located between the lateral and posterior intermuscular septa. Contains the flexor muscles of the thigh.

Anterior Compartment of Thigh

• The anterior compartment of the thigh is located between the medial and lateral intermuscular septa.
• It is also known as the extensor compartment because it contains the muscles responsible for knee extension.

Contents

Anterior compartment of thigh contains:

Muscles

1. Rectus femoris
2. Vastus medialis
3. Vastus intermedius
4. Vastus lateralis
5. Sartorius
6. Articularis genu
7. Tensor fasciae latae

Nerve

1. Femoral nerve

Artery

1. Femoral artery

Fascial Spaces

1. Femoral triangle
2. Adductor canal

Muscles of Anterior Compartment of Thigh

The anterior compartment of the thigh contains the following muscles:

1. Rectus femoris
2. Vastus lateralis
3. Vastus medialis
4. Vastus intermedius
5. Articularis genu
6. Sartorius
7. Tensor fasciae latae

Quadriceps Femoris

• The quadriceps femoris is a four-headed muscle group formed by the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius.
• These muscles converge into the quadriceps tendon, enclosing the patella, and continue as the patellar ligament to insert on the tibial tuberosity.
• The patella, the largest sesamoid bone in the body, develops within the quadriceps tendon.

Nerve supply

All muscles of the quadriceps femoris are supplied by the femoral nerve.

Actions

1. Extends the leg at the knee joint.
2. Assists in rising from a sitting or squatting position by extending the knee.
3. Helps stabilize the knee joint during standing and walking.

Clinical testing

The muscle is tested by asking the patient to extend the knee against resistance while the examiner palpates the contracting quadriceps.

Strengthening exercises (physiotherapy)

• Quadriceps strengthening exercises are important during rehabilitation after fractures, knee injuries, or paralysis.
• Common exercises include:
  1. Passive knee extension
  2. Straight leg raise
  3. Squats
  4. Step-up exercises.

Sartorius

• The sartorius is the longest muscle in the human body and is commonly known as the tailor’s muscle.
• It assists in assuming the cross-legged (tailor’s) position, which involves:

1. Flexion of the hip
2. Flexion of the knee
3. Abduction of the thigh
4. Lateral rotation of the thigh

Origin

• Arises from the anterior superior iliac spine (ASIS) and the upper half of the notch below the ASIS.
• The muscle fibers run obliquely downward and medially across the anterior thigh.
• Near the knee, the tendon passes behind the medial condyle of the femur, then curves forward to reach the medial side of the tibia.

Insertion

Inserts on the upper part of the medial surface of the tibia, anterior to the insertions of the gracilis and semitendinosus (forming part of the pes anserinus).

Innervation (nerve supply)

• Sartorius is supplied by anterior division of femoral nerve.

Actions

• As a long, slender muscle, the sartorius is a weak but versatile muscle.
• It:
  1. Flexes the hip joint
  2. Flexes the knee joint
  3. Abducts the thigh
  4. Laterally rotates the thigh

Rectus Femoris

• The rectus femoris is a straight, fusiform, bipennate muscle located in the center of the anterior thigh.
• It is the only quadriceps muscle that crosses both the hip and knee joints.

Origin

• The muscle has two heads:
  • Straight head: Arises from the upper half of the anterior inferior iliac spine (AIIS).
  • Reflected head: Arises from the groove above the acetabular margin and the capsule of the hip joint.

• The superficial fibers are bipennate, while the deep fibers are parallel.
• Both heads unite to form a fusiform muscle belly, which continues inferiorly as a flat tendon (aponeurosis).

Insertion

Inserts into the base of the patella through the quadriceps tendon and continues to the tibial tuberosity via the patellar ligament.

Innervation

• It is supplied by the posterior division of femoral nerve.

Actions

1. Flexes the hip joint.
2. Extends the knee joint.
3. Plays an important role in kicking, running, and jumping.

Vastus Lateralis

The vastus lateralis (vastus externus) is the largest muscle of the quadriceps femoris. It forms the prominent muscle mass on the lateral side of the thigh.

Origin

• It arises in a linear fashion from the:
  1. Upper part of the intertrochanteric line
  2. Anterior and inferior borders of the greater trochanter
  3. Lateral lip of the gluteal tuberosity
  4. Upper half of the lateral lip of the linea aspera

• The upper fibers arise from an aponeurosis, from which the muscle fibers originate.
• The fibers descend downward and medially toward the patella, forming a bulky muscle on the lateral aspect of the thigh.

Insertion

Inserts into the:

• Lateral part of the base and upper one-third of the lateral border of the patella
• Capsule of the knee joint
• Tibia
• Iliotibial tract (through a few fibers)

Innervation

• Vastus lateralis is supplied by posterior division of femoral nerve.

Actions

• Extends the leg at the knee joint.
• Stabilizes the patella during knee movements.
• Contributes to the powerful extension of the knee during activities such as walking, running, jumping, and climbing stairs.

Vastus Medialis (Vastus Medialis Obliques)

• The vastus medialis, also called the vastus internus or teardrop muscle, is a component of the quadriceps femoris.

Origin

• It arises in a linear fashion from the:
  • Lower part of the intertrochanteric line
  • Spiral line
  • Medial lip of the linea aspera
  • Upper two-thirds of the medial supracondylar line
• The muscle fibers descend obliquely downward and laterally. It forms a prominent bulge above the medial side of the knee, giving the characteristic teardrop appearance.

Insertion

It inserts into the:

• Medial part of the base of the patella
• Upper two-thirds of the medial border of the patella
• Capsule of the knee joint

Innervation

• Vastus medialis is supplied by posterior division of the femoral nerve.

Actions

• Extends the leg at the knee joint.
• Prevents lateral displacement of the patella, thereby maintaining patellar stability.
• Assists in the locking mechanism of the knee by producing medial rotation of the femur during the final phase of knee extension.

Vastus Intermedius

• The vastus intermedius is a component of the quadriceps femoris and lies deep to the rectus femoris in the anterior compartment of the thigh.
• It becomes visible after reflecting the rectus femoris, making this an important dissection landmark.

Origin

• It arises from the upper three-fourths of the anterior and lateral surfaces of the shaft of the femur.
• The muscle fibers run vertically downward and form a flat tendon in the lower part of the thigh.

Insertion

• Inserts into the base of the patella through the quadriceps tendon and continues to the tibial tuberosity via the patellar ligament.

Nerve Supply

• It is supplied by the posterior division of the femoral nerve.

Action

• Extends the leg at the knee joint.

Articularis Genu (Subcrureus)

• The articularis genu (subcrureus) is a small muscle composed of 3–4 muscular slips. It lies deep to the vastus intermedius and is often considered a detached part of this muscle.

Origin

• It arises from the lower part of the anterior surface of the femur.

Insertion

• It inserts into the upper part of the synovial membrane of the knee joint.

Nerve Supply

• It is supplied by a small branch to the vastus medialis from the posterior division of the femoral nerve.

Action

• It pulls the synovial membrane of the knee joint upward during knee extension, preventing it from being pinched or damaged between the articular surfaces.

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