Knee joint

Dr Sonal Udayasiri and Dr Shu Su et al.

The knee joint is a modified hinge joint between the femur, tibia and patella. It is the largest synovial joint in the body and allows flexion and extension of the leg as well as some rotation in the flexed position.

  • location: two condylar joints between femur and tibia; saddle joint between patella and femur
  • blood supply: main supply are the genicular branches of the popliteal artery
  • nerve supply: branches from the femoral, tibial, common peroneal and obturator nerves
  • movement: flexion to 150°, extension to 5-10° hyperextension; rotation whilst in the flexed position to 10° actively and 60° passively 

Two condylar joints between the femur and tibia:

  • medially: between a narrow and curved femoral condyle, and an oval tibial articular surface with a long anteroposterior length
  • laterally: between a wide and flat femoral condyle; and a circular tibial articular surface
  • the knee menisci are shaped accordingly 

Saddle joint between the patella and femoral condyles: 

  • the patella is divided into lateral, middle and medial areas by ridges
  • in extension: the lateral patella surface articulates with the lateral femoral condyle
  • in flexion: the medial patella surface articulates with the medial femoral condyle and the middle patella surface faces the intercondylar notch

The knee is supplied by anastomoses of:

  • five genicular branches of the popliteal artery (main supply)
    • medial and lateral superior genicular arteries encircle the femoral condyle
    • medial and lateral inferior genicular arteries encircle the tibial condyle
    • middle genicular artery supplies the anterior and posterior cruciate ligaments 
  • descending branch of the lateral circumflex femoral artery
  • descending genicular branch of the femoral artery
  • circumflex fibular branches of the posterior tibial artery
  • anterior and posterior recurrent branches of the anterior tibial artery 

The nerve supply to the knee is derived from:

  • branches of the femoral nerve to vastus medialis, intermedius, and lateralis
  • genicular branches of the tibial and common peroneal nerves
  • branch from the posterior division of the obturator nerve

See knee radiograph (an approach)

Anatomy: Lower limb
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Article information

rID: 31365
Section: Anatomy
Tag: knee
Synonyms or Alternate Spellings:

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Cases and figures

  • Case 1: normal knee MRI (axial)
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  • Case 1: normal knee MRI (sagittal)
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