Let’s learn about the structure of the knee joint (articulatio genus).

It connects three bones: the femur (femur), tibia (tibia) and patella (patella).

This joint includes two separate joints.

The first is the tibiofemoral joint, which is formed between the articular surfaces on the condyles of the femur (facies articularis condyli femoris) and the superior articular surface of the tibia (facies articularis superior tibiae).

The second is the patellofemoral joint, which is formed between the patellar surface of the femur (facies patellaris) and the articular surface of the patella (facies articularis patellae).

The articular capsule of the knee joint is thin and elastic, it is attached to the femur anteriorly slightly above the patellar surface, and laterally along the epicondyles, leaving them outside the joint cavity. On the tibia and patella it is attached along the margin of the articular surfaces.

According to the classification, the joint is bicondylar, biaxial, complex, and not combined.

The following range of motions is possible in the joint:

• around the frontal axis: flexion and extension

• around the vertical axis: rotation, but provided that the lower limb is flexed

  The fixing apparatus of the joint is represented by several ligaments:

• These include the fibular collateral ligament (ligamentum collaterale fibulare), which arises from the lateral epicondyle of the femur and inserts into the lateral surface of the head of the fibula.

  

  

  

• The tibial collateral ligament (ligamentum collaterale tibiale), which arises from the medial epicondyle of the femur and inserts into the medial margin of the tibia.

  

  

  

• The patellar ligament (ligamentum patellae) is located between the patella and the tibial tuberosity, which is part of the tendon of the quadriceps femoris.

  

  

  

• The oblique popliteal ligament (ligamentum popliteum obliquum) is located on the posterior side of the articular capsule, arises from the medial condyle of the tibia, weaves into the articular capsule and inserts into the posterior surface of the femur above its lateral condyle.

  

• The arcuate popliteal ligament (ligamentum popliteum arcuatum) is located on the posterior surface of the joint, arises from the posterior side of the head of the fibula and the lateral epicondyle of the femur, arches in the medial side and inserts into the posterior surface of the tibia.

  

  The composition of the additional structures of the knee joint is quite extensive. They include several formations.

  First of all, these are intra-articular cartilages, or the socalled menisci:

• The lateral meniscus (meniscus lateralis)

  

  

  

• The medial meniscus (meniscus medialis)

  

  

  

  The external thick margin of each meniscus is fused to the capsule, and the thin margin faces inside the joint. The menisci are attached to the intercondylar eminence of the tibia, and the anterior borders of the menisci are connected by the transverse ligament of the knee (ligamentum transversum genus).

  

  In addition to the menisci, several ligaments belong to the additional structures:

• The anterior cruciate ligament (ligamentum cruciatum anterius) arises from the medial surface of the lateral condyle of the femur and attaches to the anterior intercondylar area of the tibia.

  

  

• The posterior cruciate ligament (ligamentum cruciatum posterius) arises from the lateral surface of the medial condyle, and inserts into the posterior intercondylar area of the tibia.

  

  

• The transverse ligament of the knee (ligamentum transversum genus)

  

  Two meniscofemoral ligaments:

• The anterior meniscofemoral ligament (ligamentum meniscofemorale anterius)

  

• The posterior meniscofemoral ligament (ligamentum meniscofemorale posterius)

  

  And two ligaments supporting the patella:

• The medial patellar retinaculum (retinaculum patellae mediale)

  

• The lateral patellar retinaculum (retinaculum patellae laterale)

  

  Also , several synovial folds belong to the additional structures:

• The alar folds (plicae alares) are located inferiorly and laterally to the patella, they seem to be embedded in the joint cavity between the articulating bones.

  

• The infrapatellar synovial fold (plica synovialis infrapatellaris) goes from the patella down to the anterior intercondylar area, dividing the joint cavity into left and right parts.

  

  

  Several synovial bursae are connected to the knee joint cavity.

• The suprapatellar articular bursa (bursa suprapatellaris) is located between the distal epiphysis of the femur and the tendon of the quadriceps femoris.

• The deep infrapatellar bursa (bursa infrapatellaris profunda) lies between the patellar ligament and the proximal epiphysis of the tibia.

  

• The popliteal bursa (bursa musculi poplitei)

• The lateral subtendinous bursa of the gastrocnemius (bursa subtendinea musculi gastrocnemii lateralis)

• The medial subtendinous bursa of the gastrocnemius (bursa subtendinea musculi gastrocnemii medialis)

  

• The semimembranosus bursa (bursa musculi semimembranosi)

  There are also several bursae that are not communicated with the joint.

• The subcutaneous prepatellar bursa (bursa subcutanea prepatellaris) is located on the anterior surface of the knee joint, at the level of the patella in the layer of subcutaneous tissue

• The subtendinous prepatellar bursa (bursa prepatellaris subtendinea)

• The superior bursa of the biceps femoris (bursa musculi biceps femoris superior)

• The inferior bursa of the biceps femoris (bursa musculi biceps femoris inferior)

  The following vessels and nerves take part in the blood supply and innervation of the joint.

• Arteries: descending genicular artery (a. genus descendens), lateral circumflex femoral artery (a. circumflexae femoris lateralis), popliteal artery (a. poplitea), anterior tibial artery (a. tibialis anterior), posterior tibialis artery (a. tibialis posterior)

• Veins: the blood outflows through the veins with the same name

• Nerves: sciatic nerve (n. ischiadicus)

Dictionary

Knee joint

Knee joint

articulatio genus

Femur

femur

Tibia

tibia

Patella

patella

Articular surfaces on the condyles of the femur

facies articularis condyli femoris

Superior articular surface of the tibia

facies articularis superior tibiae

Patellar surface of the femur

facies patellaris

Articular surface of the patella

facies articularis patellae

Fibular collateral ligament

ligamentum collaterale fibulare

Tibial collateral ligament

ligamentum collaterale tibiale

Patellar ligament

ligamentum patellae

Oblique popliteal ligament

ligamentum popliteum obliquum

Arcuate popliteal ligament

ligamentum popliteum arcuatum

Lateral meniscus

meniscus lateralis

Medial meniscus

meniscus medialis

Transverse ligament of the knee

ligamentum transversum genus

Anterior cruciate ligament

ligamentum cruciatum anterius

Posterior cruciate ligament

ligamentum cruciatum posterius

Transverse ligament of the knee

ligamentum transversum genus

Anterior meniscofemoral ligament

ligamentum meniscofemorale anterius

Posterior meniscofemoral ligament

ligamentum meniscofemorale posterius

Medial patellar retinaculum

retinaculum patellae mediale

Lateral patellar retinaculum

retinaculum patellae laterale

Alar folds

plicae alares

Infrapatellar synovial fold

plica synovialis infrapatellaris

Suprapatellar articular bursa

bursa suprapatellaris

Deep infrapatellar bursa

bursa infrapatellaris profunda

Popliteal bursa

bursa musculi poplitei

Lateral subtendinous bursa of the gastrocnemius

bursa subtendinea musculi gastrocnemii lateralis

Medial subtendinous bursa of the gastrocnemius

bursa subtendinea musculi gastrocnemii medialis

Semimembranosus bursa

bursa musculi semimembranosi

Subcutaneous prepatellar bursa

bursa subcutanea prepatellaris

Subtendinous prepatellar bursa

bursa prepatellaris subtendinea

Superior bursa of the biceps femoris

bursa musculi biceps femoris superior

Inferior bursa of the biceps femoris

bursa musculi biceps femoris inferior

Descending genicular artery

a. genus descendens

Lateral circumflex femoral artery

a. circumflexae femoris lateralis

Popliteal artery

a. poplitea

Anterior tibial artery

a. tibialis anterior

Posterior tibialis artery

a. tibialis posterior

Sciatic nerve

n. ischiadicus