Thigh, knee, and popliteal fossa

Last updated: June 28, 2023

Summarytoggle arrow icon

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 the anterior, posterior, and medial (adductor) compartments, 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.

Overviewtoggle arrow icon

The femurtoggle arrow icon


Important landmarks

Muscles of the thightoggle arrow icon


The deep fascia of the thigh separates the muscles into three compartments:

Anterior compartment of the thigh

Anterior compartment of the thigh
Muscle Origin Insertion Nerve Function



Quadriceps femoris

Vastus lateralis
  • Greater trochanter, intertrochanteric line, gluteal tuberosity, and linea aspera
  • Extension of the flexed knee against resistance
Vastus medialis
Vastus intermedius
  • Anterolateral surface of the upper two-thirds of the femural shaft
Rectus femoris

Muscles of the posterior abdominal wall

  • Ala of the sacrum and iliac fossa
Psoas major
Psoas minor
  • Iliopubic ramus
  • Cannot be tested in isolation

Posterior compartment of the thigh

Posterior compartment of the thigh (hamstrings)

Muscle Origin Insertion Nerve Function Testing
  • Superomedial surface of tibia
Biceps femoris

Medial compartment of the thigh

Medial compartment of the thigh (adductor compartment)

Muscle Origin Insertion Nerve Function Testing

Obturator externus

  • Greater trochanter
  • Cannot be tested in isolation
  • Inferior pubic ramus
  • Superomedial aspect of the tibia
  • Pectineal line of the pubis
  • Pectineal line of the femur
  • Cannot be tested in isolation
Adductor magnus
  • Hamstring part: adductor tubercle and supracondylar line of the femur
  • Adductor part: linea aspera
  • Adduction of the thigh against resistance with the knee in extension
Adductor longus
Adductor brevis
Adductor minimus
  • Inferior ramus of pubis

Femoral triangle and fasial compartments of the thightoggle arrow icon

Femoral triangle

Venous close to penis. Nerves close to hip curves.

NAVEL: Nerve, Artery, Vein, Empty space (femoral canal), and Lymphatics (order of the femoral triangle contents, from lateral to medial).

Femoral canal

Femoral sheath

Femoral ring

Adductor canal

Saphenous opening

Vascular supply of the thightoggle arrow icon


Femoral artery

Femoral artery branches

Obturator artery


Innervation of the thightoggle arrow icon

Motor and sensory innervation

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

Motor and sensory innervation of the thigh

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

Femoral nerve

Obturator nerve

Sciatic nerve
Pure sensory nerves

Lateral cutaneous nerve of thigh (lateral femoral cutaneous nerve)

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

Posterior cutaneous nerve of thigh (posterior femoral cutaneous nerve)

  • None

Dermatomal distribution of the thigh and knee

Lymphatic drainage of the thightoggle arrow icon

Inguinal lymph node groups

The knee jointtoggle arrow icon


Soft tissue structures of the knee

Ligaments and menisci

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
  • Cannot be tested in isolation
Anterolateral ligament
  • Cannot be tested in isolation
(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.

To remember the orientation of the cruciate ligaments, cross your middle finger over the index finger of the same hand and hold your hand over the ipsilateral knee. The middle finger represents the ACL (from lateral femoral condyle to anterior tibia) and the index finger represents the PCL (from medial femoral condyle to posterior tibia).


Bursae of the knee

Bursae Anatomy Clinical significance
Suprapatellar bursa
Prepatellar bursa
Infrapatellar bursa

Anserine bursa

3-D model of the knee


The popliteal fossatoggle arrow icon


Referencestoggle arrow icon

  1. Claes S, Vereecke E, Maes M, Victor J, Verdonk P, Bellemans J. Anatomy of the anterolateral ligament of the knee. J Anat. 2013; 223 (4): p.321-328.doi: 10.1111/joa.12087 . | Open in Read by QxMD
  2. Chung KW, Chung HM. Gross Anatomy. Lippincott Williams & Wilkins ; 2012
  3. Markov K, Zaharieva M, Dragieva P, et al. Unilateral psoas minor: a case report. Scripta Scientifica Vox Studentium. 2017; 1 (1): p.47.doi: 10.14748/ssvs.v1i1.4097 . | Open in Read by QxMD
  4. Murinova N, Krashin D, Trescot AM. Posterior Femoral Cutaneous Nerve Entrapment: Pelvic. Springer International Publishing ; 2016: p. 491-498
  5. Standring S. Gray's Anatomy: The Anatomical Basis of Clinical Practice. Elsevier Health Sciences ; 2016

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