Thigh

The thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments. The thigh is supplied primarily by the femoral artery and its branches, drained by deep and superficial venous networks, and innervated by branches of the lumbar and sacral plexuses.

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Bone of the Thigh: Femur

  • The longest and strongest bone in the human body
  • The only bone located in the thigh
  • Articulations of the femur:
    • With the acetabulum of the hip bone proximally: to form the hip joint
    • With the tibia distally: to form medial and lateral tibiofemoral articulations
    • With the patella distally: to form the patellofemoral articulation
SegmentImportant landmarks
Proximal end
  • Head:
    • Spherical
    • Articulates with acetabulum to form the hip joint
    • Has the fovea for the ligament of the head on its posteroinferior surface
  • Neck:
    • Approximately 5 cm in length
    • Subdivided into 3 regions: the basicervical, midcervical, and subcapital portions
    • Fractures here may lead to avascular necrosis.
  • Greater and lesser trochanters:
    • Sites of attachment for muscles of the hip, pelvis, and thigh
    • Connected by the intertrochanteric line anteriorly and the intertrochanteric crest posteriorly
Shaft
  • Cylindrical
  • Convex anteriorly and concave posteriorly
  • Linea aspera: a longitudinal ridge found on the posterior surface made up of a medial and a lateral lip
Distal end
  • Patellar surface:
    • Anterior depression
    • Provides a gliding surface for the patella (knee cap)
  • Medial and lateral condyles: articulate with the tibia to form the knee joint
  • Intercondylar fossa:
    • Separates the condyles of the distal femur posteriorly
    • Site of attachment for stabilizing ligaments of the knee

Fascial Compartments of the Thigh

The iliotibial tract or iliotibial band is a thickening of the fascia lata located on the lateral surface of the thigh. The iliotibial tract is a stabilizer of the hip and knee.

  • Proximally: 
    • Splits into a superficial and deep layer, enclosing the tensor fascia latae muscle
    • Attaches proximally to the iliac crest of the pelvis
  • Distally: 
    • Merges with the aponeurosis of the vastus lateralis muscle
    • Attaches to Gerdy’s tubercle on the lateral tibial condyle
Lateral view of the thigh

Lateral view of the thigh, featuring the iliotibial tract and tensor fasciae latae muscle

Image by BioDigital, edited by Lecturio.

The 3 intermuscular septa arise from the fascia lata and attach to the linea aspera of the femur. The lateral, medial, and posterior intermuscular septums divide the thigh into the following:

  1. The anterior or extensor compartment:
    • Quadriceps (rectus femoris, vastus lateralis, vastus intermedius, and vastus medialis)
    • Sartorius
  2. The posterior or flexor compartment:
    • Biceps femoris
    • Semitendinosus
    • Semimembranosus
  3. The medial or adductor compartment:
    • Adductor magnus
    • Adductor longus
    • Adductor brevis
    • Gracilis
    • Pectineus
Thigh cross-section at mid-shaft

Thigh cross-section at mid-shaft

Image by Lecturio.

Anterior Compartment of the Thigh

  • The anterior compartment of the thigh contains the following muscles:
    • Quadriceps femoris: comprises the rectus femoris, vastus medialis, vastus intermedius, and vastus lateralis
    • Sartorius
    • Sometimes, the iliopsoas is considered part of the anterior compartment; otherwise, it is considered a muscle of the hip joint/pelvis.
  • The primary function of the muscles of the anterior compartment of the thigh is knee extension.
  • All these muscles all innervated by the femoral nerve.
MuscleOriginInsertionInnervationFunction
Rectus femorisAnterior inferior iliac spineTibial tuberosity via common quadriceps and patellar ligamentFemoral nerve (L3, L4)
  • Extend the leg at the knee
  • Rectus femoris can also support the iliopsoas in hip flexion.
Vastus lateralisGreater trochanter and the lateral lip of linea aspera
Vastus intermediusAnterior shaft of the femur
Vastus medialisIntertrochanteric line and medial lip of linea aspera
SartoriusAnterior superior iliac spineMedial surface of the proximal tibiaFemoral nerve (L2)
  • Flexes, abducts, and laterally rotates the hip
  • Flexes the knee

Posterior Compartment of the Thigh

  • The posterior compartment of the thigh contains the hamstring muscles:
    • Biceps femoris
    • Semitendinosus
    • Semimembranosus
  • The muscles of the posterior compartment have the primary function of knee flexion and hip extension.
  • These muscles are innervated by branches of the sciatic nerve.
MuscleOriginInsertionInnervationFunction
Biceps femoris
  • Long head: ischial tuberosity
  • Short head: linea aspera and lateral supracondylar line
Lateral surface of the fibula
  • Long head: tibial division of sciatic nerve (L5, S1)
  • Short head: common fibular division of sciatic nerve (S1)
  • Flexes and laterally rotates the knee when flexed
  • Extends the hip
SemitendinosusIschial tuberosityMedial surface of the proximal tibiaTibial division of sciatic nerve (L5, S1)Extends the hip, flexes the knee, and medially rotates the knee when flexed
SemimembranosusPosterior surface of medial condyle of tibia

Medial Compartment of the Thigh

  • The medial compartment of the thigh contains the following muscles:
    • Adductor magnus, longus, and brevis
    • Gracilis
    • Pectineus
    • The obturator externus is sometimes included, although it is primarily an external rotator and secondarily an adductor.
  • The primary function of the muscles of the medial compartment is hip adduction.
  • These muscles are primarily innervated by the obturator nerve, except for the pectineus (femoral nerve).
MuscleOriginInsertionInnervationFunction
Adductor magnus
  • Adductor portion (AP): ischiopubic ramus
  • Hamstring portion (HP): ischial tuberosity
  • AP: linea aspera
  • HP: adductor tubercle
  • AP: obturator nerve (L3, L4)
  • HP: tibial nerve (L4)
  • AP: adducts the hip
  • HP: extends the hip
Adductor longusBody of pubisMiddle &frac13 of linea asperaObturator nerve (L3)Adducts the hip
Adductor brevisBody and inferior ramus of pubisProximal linea aspera
GracilisMedial surface of the proximal tibiaObturator nerve (L2)
  • Adducts the hip
  • Flexes the knee
PectineusSuperior pubic ramusPectineal line of femurFemoral nerve (L2)Adducts, flexes, and supports medial rotation of the hip

Pes anserinus

The distal end of the medial region of the thigh is the location of the pes anserinus or “goose foot,” which comprises the conjoined tendons of the sartorius, gracilis, and semitendinosus muscles inserting into the tibia.

Blood Supply

Arterial blood supply

Three arteries exit the pelvis: the femoral, obturator, and inferior gluteal arteries. However, the femoral and obturator arteries continue toward the thigh, while the inferior gluteal supplies and ends in the gluteal region.

  • Femoral artery: 
    • Supplies the majority of the lower limb
    • A direct continuation of the external iliac artery
    • Originates and enters the thigh upon passing under the inguinal canal 
    • Passes through the femoral triangle, where it can be palpated
    • Enters the adductor canal distally in the thigh, terminates at the adductor hiatus, and becomes the popliteal artery
    • Has several branches:
      • Profunda femoris artery (deep artery of the thigh): the main branch of the femoral; supplies most of the structures in the thigh and gives off perforating branches and the medial and lateral circumflex femoral arteries (MCFAs and LCFAs) to the hip joint
      • Superficial epigastric artery
      • Superficial circumflex iliac artery
      • Superficial external pudendal artery
      • Deep external pudendal artery
  • Obturator artery: 
    • Branch of the internal iliac artery
    • Passes through the obturator foramen to the muscles of the medial compartment
    • Gives off important extra-pelvic branches:
      • Anterior branch: supplies the obturator externus muscle, adductor muscles, and skin over the medial thigh
      • Posterior branch: supplies the muscles attached to the ischial tuberosity
      • Artery of the ligamentum teres: supplies the head of the femur

Venous drainage

  • Deep venous system:
    • The popliteal vein becomes the femoral vein as it ascends into the thigh.
    • The femoral vein accompanies the femoral artery in its trajectory and receives the deep vein of the thigh (profunda femoris vein) in the proximal thigh.
    • The femoral vein becomes the external iliac vein once it passes underneath the inguinal ligament.
  • Superficial venous system: 
    • The great saphenous vein originates from the dorsal venous arch of the foot.
    • Ascends the medial side of the leg passing posterior to the medial condyle at the knee
    • Drains into the femoral vein in the femoral triangle

Innervation

The thigh is innervated by branches of the lumbar and sacral plexus.

NerveOriginMotor supplySensory supply
Lateral femoral cutaneous nerveLumbar plexus (L2–L3)Skin of the anterolateral thigh
Posterior femoral cutaneous nerveSacral plexus (S2–S3)Skin of the gluteal region, posterior perineum, and posterior thigh
Femoral nerve
  • Largest branch of the lumbar plexus
  • Dorsal branches of L2–4 ventral rami
  • Muscles of anterior compartment
  • Iliacus
  • Pectineus
  • Skin of anterior thigh
  • Skin of lower &frac23 of medial thigh
Saphenous nerveBranch of the femoral nerveSkin of lower &frac23 of the medial thigh, medial lower leg, and foot
Obturator nerve
  • Lumbar plexus
  • Ventral branches of L2-4 ventral rami
Muscles of the medial compartmentSkin of upper &frac13 of the medial thigh
Sciatic nerve (thickest nerve in the human body)
  • Sacral plexus (L4–S3)
  • Enters posterior thigh through the greater sciatic foramen
Tibial branch: Muscles of the posterior compartmentNone in the thigh
Lower limb nerves

Innervation of the lower limbs

Image by Lecturio.

Clinical Relevance

The following conditions are clinically relevant to the thigh:

  • Femoral shaft fracture: a fracture anywhere along the shaft or diaphysis of the femur. Femoral shaft fractures generally occur in young adults due to high-impact injuries. In the elderly, these fractures are usually due to low-impact falls, even a fall from standing, and are related to osteoporosis. Typically present as a painfully swollen, tense thigh with restricted range of motion. Vascular compromise secondary to blood loss and fat embolization are possible complications.
  • Proximal femur fractures: most commonly seen in the elderly and related to osteoporosis. Generally classified into intracapsular and extracapsular fractures; intracapsular fractures may lead to avascular necrosis of the femoral head.
  • Femoral hernia: an uncommon type of groin hernia, in which intraabdominal contents herniate under the inguinal ligament and through the femoral ring into the femoral canal. More common in adults than in children, femoral hernias usually present with swelling that worsens with coughing or straining and that protrudes into the femoral triangle (inferiorly to the inguinal ligament and medial to the femoral vein).

References

  1. Drake, R.L., Vogl, A.W., & Mitchell, A.W.M. (2014). Gray’s Anatomy for Students (3rd ed.). Philadelphia, PA: Churchill Livingstone.
  2. Bordoni, B., & Varacallo, M. Anatomy, Bony Pelvis and Lower Limb, Thigh Quadriceps Muscle. [Updated 2020 Jul 27]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan. Retrieved from: https://www.ncbi.nlm.nih.gov/books/NBK513334/
  3. Khan, A., & Arain, A. Anatomy, Bony Pelvis and Lower Limb, Anterior Thigh Muscles. [Updated 2020 Aug 15]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan. Retrieved from: https://www.ncbi.nlm.nih.gov/books/NBK538425/

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