Thigh, knee, and popliteal fossa

The femur

Overview

  • The femur is the longest and strongest bone of the body.
  • It articulates with:

Important landmarks

  • Head
  • Neck: connects the head to the shaft of the femur
  • Greater trochanter: lies on the lateral aspect of the junction between the neck and shaft of the femur
  • Lesser trochanter: lies on the posteromedial aspect of the junction between the neck and shaft of the femur
  • Shaft:
    • Linea Aspera: ridge seen on the posterior aspect of the shaft
    • Pectineal line: medial border of the linea aspera to which the pectineus muscle is attached
    • Adductor tubercle: a prominence above the medial femoral condyle to which the adductor magnus muscle is attached
  • Distal end
    • Medial and lateral condyles
      • The inferior surface articulates with the tibial condyles to form the knee joint.
      • The anterior surface articulates with the patella to form the patellofemoral joint.
    • Intercondylar fossa: groove between the condyles to which the anterior and posterior cruciate ligaments are attached

Muscles of the thigh

  • The deep fascia of the thigh separates the muscles into three compartments
    • Anterior compartment
      • Common nerve supply: femoral nerve
      • Common function: knee extension
    • Posterior compartment
      • Common origin: the ischial tuberosity
      • Common nerve supply: tibial part of the sciatic nerve
      • Common function: hip extension and knee flexion
    • Medial compartment
Anterior compartment of the thigh
Muscle Origin Insertion Nerve Function

Testing

Sartorius
  • Anterior-superior iliac spine
  • Medial upper side of the tibia
  • Hip: flexion, abduction, external rotation
  • Knee: flexion
  • Abduct, flex and externally rotate the thigh against resistance

Quadriceps femoris

Vastus lateralis
  • Greater trochanter, intertrochanteric line, gluteal tuberosity, and linea aspera
  • Lateral side of the patella via the quadriceps tendon
  • Knee: extension
  • Extend the flexed knee against resistance
Vastus medialis
  • Linea aspera, intertrochanteric line, pectineal line
  • Medial side of the patella via the quadriceps tendon
  • Knee: extension
Vastus intermedius
  • Anterolateral surface of the tibia
  • Superolateral part of the patella via the quadriceps tendon
  • Knee: extension
Rectus femoris
  • Hip: flexion
  • Knee: extension

Muscles of the posterior abdominal wall

Iliacus
  • Ala of the sacrum and iliac fossa
  • Lesser trochanter of the femur via the iliopsoas tendon
  • Hip: flexion
  • Flex the hip further (i.e., bring the thigh above the hip), against resistance
  • Clinical significance: iliopsoas abscess
Psoas major
  • Transverse processes of vertebrae T12–L5
  • L2–L3 lumbar plexus
  • Hip: flexion
  • Trunk: lateral flexion
Psoas minor
  • Vertebral bodies of T12 and L1
  • Iliopubic ramus
  • Trunk: flexion (weak)
  • Cannot be tested in isolation

Posterior compartment of the thigh

(Hamstrings)

Muscle Origin Insertion Nerve Function Testing
Semimembranosus
  • Ischial tuberosity
  • Medial condyle of the tibia
  • Hip: extension
  • Knee: flexion, internal rotation
  • 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
  • Hip: extension
  • Knee: flexion, external rotation

Medial compartment of the thigh

(Adductor compartment)

Muscle Origin Insertion Nerve Function Testing

Obturator externus

  • Greater trochanter
  • Hip: external rotation and adduction
  • Cannot be tested in isolation
Gracilis
  • Inferior pubic ramus
  • Superomedial aspect of the tibia
  • Hip: adduction and flexion
  • Knee: flexion and internal rotation
  • The tendon becomes palpably taut on flexion and internal rotation of the knee
Pectineus
  • Pectineal line of the pubis
  • Pectineal line of the femur
  • Hip: flexion, adduction, and external rotation
  • Cannot be tested in isolation
Adductor magnus
  • Hamstring part: ischial tuberosity
  • Adductor part: ischiopubic ramus
  • Hamstring part: adductor tubercle and supracondylar line of the femur
  • Adductor part: linea aspera
  • Hamstring part: extension of the hip
  • Adductor part: adduction of the hip
  • Adduct the thigh against resistance with the knee in extension
Adductor longus
  • Linea aspera
  • Hip: adduction and flexion
Adductor brevis
  • Linea aspera
  • Hip: adduction and flexion
Adductor minimus
  • Inferior ramus of pubis
  • Linea aspera
  • Hip: adduction, flexion, and external rotation

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

  • Definition: A cylindrical space enclosed within the femoral sheath that contains loose areolar tissue and lymphatics.
  • Boundaries
    • Anterior: inguinal ligament
    • Posterior: pubic ramus and pectineal ligament
    • Medial: lacunar ligament
    • Lateral: femoral vein
    • Femoral canal is wider in women
  • Clinical significance

Femoral sheath

Femoral ring

  • Definition: the abdominal opening of the femoral canal
  • Boundaries
    • Anterior: inguinal ligament
    • Posterior: pectineal ligament
    • Medial: lacunar ligament
    • Lateral: medial border of the femoral vein

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 and sacral plexuses

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

Femoral nerve

  • Largest branch of the lumbar plexus
  • Nerve roots: dorsal branches of L2–4 ventral rami
  • Intermediate cutaneous nerve of thigh: skin over the anterior aspect of the thigh
  • Medial cutaneous nerve of thigh (medial femoral cutaneous nerve): skin over the lower 2/3rd of the medial aspect of the thigh
  • Saphenous nerve (supplies the medial side of the leg and foot)
  • Articular branch: knee joint

Obturator nerve

  • Branch of the lumbar plexus
  • Nerve roots: ventral branches of L2–4 ventral rami
  • Muscles of the medial compartment of the thigh
  • Skin over the upper 1/3rd of the medial aspect of the thigh
  • Articular branch: hip and knee joints
Sciatic nerve
  • Sacral plexus
  • Nerve roots: L4–S3
  • Enters the posterior thigh through the greater sciatic foramen
  • Thickest nerve of the body
  • Tibial part of sciatic nerve
    • Muscles of the posterior compartment of the thigh (hamstrings)
    • Hamstring portion of the adductor magnus
    • Terminal branches: divides usually at the apex of the popliteal fossa into the tibial nerve and common fibular nerves that supply the leg and foot
Pure sensory nerves

Lateral cutaneous nerve of thigh

(lateral femoral cutaneous nerve)

  • Lumbar plexus (L2–L3)
  • None
  • Skin over the anterolateral aspect of thigh (up to the knee)

Posterior cutaneous nerve of thigh

(posterior femoral cutaneous nerve)

  • Sacral plexus (S2S3)
  • None
  • Skin over the buttock, posterior part of the perineum, and posterior thigh

Dermatomal distribution of the thigh and knee

  • Anterior thigh (craniocaudal): L2, L3, L4
  • Posterior thigh (lateromedial and caudocranial): S1, S2, S3, S4
  • Anterior knee: L3, L4
  • Popliteal fossa: S1, S2

Lymphatic drainage of the thigh

Inguinal lymph node groups

The knee joint

Overview

  • Type of joint: a complex hinge type of synovial joint made up of two components
    • The tibiofemoral articulation
      • Between the condyles of the tibia and femur
      • Weight-bearing
    • The patellofemoral articulation
      • Between the anterior surface of the femoral condyles and the posterior surface of the patella
      • Not weight-bearing
  • Movements
  • Blood supply: anastomosis around the knee joint between branches of the femoral and popliteal vessels (genicular anastomosis)
  • Innervation: genicular branches of the femoral, obturator, tibial, and common peroneal nerves

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)
  • Prevents anterior displacement of the tibia on the femur
  • Limits hyperextension of the knee
  • Clinical significance: ACL injury

Posterior cruciate ligament

(PCL)

  • Origin: posterior intercondylar part of the tibia
  • Insertion: medial femoral condyle (lateral aspect)
Collateral ligaments

Medial collateral ligament

(Tibial collateral ligament; MCL)

  • Origin: medial femoral epicondyle
  • Insertion: medial tibial condyle
  • Prevents medial displacement of the tibia and femur (valgus)
  • Limits abduction of the leg at the knee joint

Lateral collateral ligament

(Fibular collateral ligament; LCL)

  • Origin: lateral femoral epicondyle
  • Insertion: head of the fibula
  • Prevents lateral displacement of the tibia and femur (varus)
  • Limits extension and adduction of the leg at the knee joint

Other ligaments of the knee

Patellar ligament

(Patellar tendon)

  • Extension of the knee
Popliteofibular ligament
  • Stabilizes the posterolateral aspect of the knee
Transverse ligament
  • Connects the anterior ends of the two menisci
  • 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
  • Between the anterior surface of the patella and the skin
Infrapatellar bursa
  • Infrapatellar bursitis (clergyman's knee)

Anserine bursa

(pes anserinus)

The popliteal fossa

Clinical significance