Kneejoint

The Knee Joint

Knee joint:1 -the largest joint in

body2 -the most complex

one {allow mobility (flexion/extension), stability(weight bearing joint) }

3-The most injured one

actually 2 joints within the articular capsule

1 -tibio-femoral2-patello-femoral

type and variety of the knee joint

•tibio-femoral joint (the articulation between the femur and tibia, which is weightbearing)

•Type: •synovial joint

Varity :modified hinge joint (flexion

and extension is primary motion , Some lateral and medial rotation (is possible when the knee is flexed

•patello-femoral joint

(the articulation between the patella and the femur)

Type: •it is saddle joint (the patella slides within

the patello-femoral groove)

Articulating Bones

FemurTibia

PatellaNot part of the knee

joint:fibula - it does not

articulate with the femur or the patella

Articular surfaces

covered by hyaline cartilageThe major surfaces are:

Lower end femur (medial and lateral femoral condyles )

upper end tibia (medial and lateral tibial condyles )

posterior aspect of the patella

Enlarged femoral condyles articulate on

enlarged tibial condyles

on the anterior surface of the of the

femur the two condyles join to form

V-shaped articular surfaces between the

femur and posterior aspect of the patella

Joint capsule

External fibrous layer (fibrous capsule)

Internal synovial membrane

The fibrous capsule capsule is extensive and thin ,However it has a few thickend part that make up the intrinsic ligaments Incomplete in some areas reinforced by extensions from tendons of the surrounding muscles

encloses the articular cavity and the intercondylar region

superiorly Attaches to the femur , proximaly to

articular margins of the condylesInferiorly Attaches to tibia , superior articular

surface (tibial plateau)

1 -anteriorly: It is absent and replaced by

quadriceps tendon, patella, and ligamentum patellae, vastus lateralis

and vastus medialis tendinons which merge

above with the quadriceps femoris tendon and below

with the patellar ligament , fibrous layer is

continuous with the lateral and medial margins of

these structures .

2 -medially: blends with the tibial

collateral ligament and is attached to the

medial meniscus restricting its mobility

4-Laterally: the fibular collateral ligament

which separated from joint capsule by fibular

bursa , the internal surface of the fibrous

membrane is not attached to the lateral

meniscus.

3-Posteriorly:enclose the condyles and the

intercondylar fossa and has an opening for popliteus tendon to pass out the joint

capsule and attach to the tibia

anterolaterally: reinforced by from the iliotibial

tractPosteromedially : reinforced by oblique

popliteal ligament which is an extension from the semimembranosus tendon

Synovial membrane

Lines the fibrous capsule medially and laterally and attaches to the margins of the articular surfaces(fermoral and tibial condyles) ,outer margins of the menisci and the posterior surface of patella ,reflects anteriorly into the intercondylar region to cover the cruciate ligaments excluding them from the articular cavity , but they are enclosed within the fibrous membraneAnteriorly, the synovial membrane is separated from the patellar ligament by an infrapatellar fat pad also

Bursae

more than 10 bursae in & around knee

bursa communicating with the articular cavity

suprapatellar bursa: a large bursa that is a continuation of the articular cavity ,superior to patella between the distal end of the shaft of femur and the quadriceps femoris muscle

subpopliteal recess: extends posterolaterally from the articular cavity and lies between the lateral meniscus and the tendon of the popliteus muscle

bursae that are not communicating with the

articular cavitysubcutanous prepatellar bursa: over the knee

capDeep infra-patellar bursae:underneath the

patellar ligament Subcutaneous or superfacial infra-patellar

bursae: over the patellar ligament

Cruciate ligaments

Cruciate ligaments(L.crux,a cross): anterior and posterior cruciate ligament that crisscross within the joint capsule in the inercondylar fossa and outside synovial cavity

anterior cruciate ligament(ACL): weaker than posterior one,attaches laterally in the inercodyar fossa to the medial side of lateral femoral condyle descend medialy to to the anteroir intercondylar area of the tibia just posterior to attachement of medial meniscus

ACL limits the sliding of tibia too far forward (thus prevent the hyperextension of knee )and femoral condyles too far backward

posterior cruciate ligament: stronger than the anteroir one, attaches medially in the inercodyar fossa to the lateral side of medial femoral condyle descend laterally to to the posterior intercondylar area of the tibia

PCL limits the sliding of tibia too far backward(thus prevent the hyperflexion of knee )and femoral condyles too far forward