Thigh

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

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

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

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.

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.

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).

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.

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).