Thigh, knee, and popliteal fossa

Summary

The lower extremity consists of the hip, thigh, knee, popliteal fossa, leg (crus), ankle, and foot. The thigh is the portion of the lower limb extending from the hip to the knee. The knee is the joint that connects the thigh and the leg (crus). The space posterior to the knee is referred to as the popliteal fossa. The femur is the long bone of the thigh, which articulates proximally with the acetabulum of the pelvis to form the hip joint and distally with the tibial condyles and the patella to form the knee joint. The muscles of the thigh are separated by intermuscular septa into an anterior, a posterior, and a medial (adductor) compartment, all of which are enclosed by the fascia lata. The anterior compartment, which is innervated by the femoral nerve, contains muscles involved in knee extension and hip flexion. The posterior compartment (hamstrings), which is innervated by the tibial part of the sciatic nerve, contains muscles involved in hip extension and knee flexion. The medial (adductor) compartment, which is innervated by the obturator nerve, contains muscles involved in hip adduction, flexion, and external rotation. The femoral triangle is a triangular intermuscular space in the anterior thigh through which pass major neurovascular structures (femoral artery, femoral vein, femoral nerve). Additional noteworthy anatomic regions in the thigh include the femoral canal, femoral ring, and adductor canal. The thigh is perfused by the femoral and obturator arteries and drained by the long saphenous vein (superficial) and the femoral vein (deep). The knee joint consists of the tibiofemoral and patellofemoral joints. Soft-tissue structures of the knee include the menisci (medial and lateral), the cruciate ligaments (anterior and posterior), the collateral ligaments (medial and lateral), and the bursae (prepatellar bursa, anserine bursa). The knee joint allows for flexion and extension of the leg as well as a certain degree of internal rotation and external rotation. The knee joint is perfused by branches of the femoral and popliteal vessels and innervated by the genicular branches of the femoral, obturator, tibial, and common peroneal nerves. The popliteal fossa is a diamond-shaped region on the posterior aspect of the knee, which contains the popliteal artery and vein and the tibial and common peroneal nerve.

The femur

Overview

Important landmarks

Muscles of the thigh

Anterior compartment of the thigh
Muscle Origin Insertion Nerve Function

Testing

Sartorius
  • Abduct, flex and externally rotate the thigh against resistance

Quadriceps femoris

Vastus lateralis
  • Greater trochanter, intertrochanteric line, gluteal tuberosity, and linea aspera
  • Extend the flexed knee against resistance
Vastus medialis
  • Linea aspera, intertrochanteric line, pectineal line
Vastus intermedius
  • Anterolateral surface of the upper two-thirds of the femural shaft
  • Superolateral part of the patella via the quadriceps tendon
Rectus femoris

Muscles of the posterior abdominal wall

Iliacus
  • Ala of the sacrum and iliac fossa
  • Lesser trochanter of the femur via the iliopsoas tendon
  • Flex the hip further (i.e., bring the thigh above the hip), against resistance
  • Clinical significance: iliopsoas abscess
Psoas major
Psoas minor
  • Iliopubic ramus

Posterior compartment of the thigh

(Hamstrings)

Muscle Origin Insertion Nerve Function Testing
Semimembranosus
  • Ischial tuberosity
  • Flex the knee against resistance
Semitendinosus
  • Superomedial surface of tibia
Biceps femoris
  • Long head: ischial tuberosity
  • Short head: upper supracondylar line and the linea aspera

Medial compartment of the thigh

(Adductor compartment)

Muscle Origin Insertion Nerve Function Testing

Obturator externus

  • Greater trochanter
Gracilis
  • Inferior pubic ramus
  • Superomedial aspect of the tibia
Pectineus
  • Pectineal line of the pubis
  • Pectineal line of the femur
Adductor magnus
  • Hamstring part: ischial tuberosity
  • Adductor part: ischiopubic ramus
  • Hamstring part: adductor tubercle and supracondylar line of the femur
  • Adductor part: linea aspera
  • Adduct the thigh against resistance with the knee in extension
Adductor longus
  • Linea aspera
Adductor brevis
  • Linea aspera
Adductor minimus
  • Inferior ramus of pubis
  • Linea aspera

Femoral triangle and fasial compartments of the thigh

Femoral triangle

To remember the order of the femoral canal contents, remember “NAVEL”: Nerve, Artery, Vein, Empty space (femoral canal), and Lymphatics

Femoral canal

Femoral sheath

Femoral ring

Adductor canal

Saphenous opening

Vascular supply of the thigh

Arteries

Femoral artery

Obturator artery

Veins

Innervation of the thigh

Motor and sensory innervation

The motor and sensory nerve of the thigh arise from the lumbar plexus and sacral plexus

Nerve Origin Motor supply Sensory supply Clinical significance
Mixed motor and sensory nerves

Femoral nerve

Obturator nerve

  • Muscles of the medial compartment of the thigh
  • Skin over the upper 1/3rd of the medial aspect of the thigh
Sciatic nerve
Pure sensory nerves

Lateral cutaneous nerve of thigh

(lateral femoral cutaneous nerve)

  • None
  • Skin over the anterolateral aspect of thigh (up to the knee)

Posterior cutaneous nerve of thigh

(posterior femoral cutaneous nerve)

  • None

Dermatomal distribution of the thigh and knee

References:[1][2]

Lymphatic drainage of the thigh

Inguinal lymph node groups

The knee joint

Overview

Soft tissue structures of the knee

Ligaments and menisci of the knee
Structure Anatomy Function Testing

Cruciate ligaments

Anterior cruciate ligament

(ACL)

  • Origin: anterior intercondylar part of the tibia
  • Insertion: lateral femoral condyle (posteromedial aspect)

Posterior cruciate ligament

(PCL)

Collateral ligaments

Medial collateral ligament

(Tibial collateral ligament; MCL)

  • Origin: medial femoral epicondyle
  • Insertion: medial tibial condyle

Lateral collateral ligament

(Fibular collateral ligament; LCL)

  • Origin: lateral femoral epicondyle
  • Insertion: head of the fibula

Other ligaments of the knee

Patellar ligament

(Patellar tendon)

  • Extension of the knee
Popliteofibular ligament
  • Stabilizes the posterolateral aspect of the knee
Transverse ligament
  • Prevents the anterior margin (horn) of the menisci from moving forward
  • Reduces the pressure exerted on the menisci by the articular surfaces of the tibia and femur
Menisci
(semilunar cartilages)
Medial meniscus
  • Deepen the articular surface and stabilize the knee joint structure
  • Decrease friction between the osseous surfaces
  • Periphery is better vascularized than the inner surface
  • Clinical significance: meniscal tear
Lateral meniscus

The unhappy triad: injury to the ACL, MCL, and medial meniscus caused by a lateral force to the knee!


Bursae of the knee

Bursae Anatomy Clinical significance
Suprapatellar bursa
Prepatellar bursa
Infrapatellar bursa

Anserine bursa

(pes anserinus)

3-D model of the knee


References:[3][4]

The popliteal fossa


References:[5][6][7]

Clinical significance