Knee Joint

Dr. Heba Kalbouneh

Associate Professor of Anatomy and Histology

Articulation between

the femur and tibia

(weight- bearing)

Articulation between

the patella and patellar

surface of femur

Allows the pull of

quadriceps femoris to

be directed anteriorly

over the knee to the

tibia without tendon

wear

Knee joint is the largest synovial joint

in the body. Consists of two joints:

Knee joint Articulating surfaces:

Quadriceps

tendon

Patellar

ligament

Tibiofemoral joint

Modified synovial hinge

(bicondylar)

Allows flexion and

extension with some

degree of medial and

lateral rotation

Patellofemoral joint

Plane gliding joint

Type:

Capsule:

The capsule is attached to the margins of

the articular surfaces and surrounds the

sides and posterior aspect of the joint.

On the front of the joint, the capsule is

absent. The capsule is completed

anteriorly by patella, ligamentum patellae,

medial and lateral patellar retinacula

Posterior view of the knee

On each side of the patella, the

capsule is completed anteriorly by

expansions from the tendons of

vastus lateralis and medialis

forming Medial and Lateral patellar

retinacula

Patellar ligament

Medial patellar

retinaculum Lateral patellar

retinaculum

The ligamentum patellae is

attached above to the lower

border of the patella and below

to the tuberosity of the tibia.

Ligaments:

Extracapsular ligaments:

Ligamentum patellae

Lateral collateral ligament

Medial collateral ligament

Oblique popliteal ligament

Intracapsular Ligaments

(within the joint cavity):

Anterior Cruciate Ligament

Posterior Cruciate Ligament

The ligaments may be

divided into those that lie

outside the capsule

(extracapsular) and those that

lie within the capsule

(intracapsular)

The lateral collateral ligament is

cordlike and is attached above to the

lateral femoral epicondyle and below

to the head of the fibula.

The medial collateral ligament is

a flat band and is attached above to

the medial femoral epicondyle and

below to the upper medial surface

of tibia.

Why???

The tendon of the popliteus

muscle intervenes between the

ligament and the lateral

meniscus

What does this mean??

Posterior view of the knee

An opening in the capsule

permits the tendon of the

popliteus to emerge

The popliteus tendon passes

between the lateral meniscus and

the capsule

The oblique popliteal ligament

is a tendinous expansion derived

from the semimembranosus

muscle. It strengthens the

posterior aspect of the capsule

Sem

imem

bra

nou

s

The cruciate ligaments

are named anterior and

posterior, according to their

tibial attachments

Anterior

Cruciate

Ligament

Posterior

Cruciate

Ligament

Cruciate: latin for

shaped like a cross

Are the main bond between the femur

and the tibia throughout the joint's

range of movement

Anterior view of the knee

The anterior cruciate ligament is

attached to the anterior intercondylar area

of the tibia and passes upward, backward,

and laterally, to be attached to the posterior

part of the lateral wall of intercondylar

fossa

The anterior cruciate ligament restricts

anterior displacement of the tibia relative

to the femur

The posterior cruciate ligament is

attached to the posterior intercondylar area

of the tibia and passes upward, forward,

and medially to be attached to the anterior

part of the medial wall of intercondylar

fossa

The anterior cruciate ligament restricts

posterior displacement of the tibia relative

to the femur

The tests for the integrity of the cruciate ligaments are

the anterior and posterior drawer signs

Tearing of the posterior cruciate ligament

allows the tibia to be easily pulled

posteriorly

(posterior drawer sign)

Tearing of the anterior cruciate ligament

allows the tibia to be easily pulled

forward

(anterior drawer sign)

Test anterior cruciate ligament

Test posterior cruciate ligament

Ruptured ACL Ruptured PCL

Menisci

Are medial and lateral C-

shaped fibrocartilages

The upper surfaces are in

contact with femoral condyles

The lower surfaces are in

contact with tibial condyles.

Their function is to deepen

the articular surfaces of the

tibial condyles to receive the

convex femoral condyles; they

also serve as cushions between

the two bones

Each meniscus is attached to

the upper surface of the tibia

by anterior and posterior horns

Superior view of the proximal end of Tibia

The medial meniscus is

attached to the capsule of the

knee joint and the medial

collateral ligament, it is

relatively immobile

Medial collateral ligament

Medial meniscus

Note

The lateral condyle of femur

is a bit longer than the medial

Helps in preventing the

lateral dislocation of patella

Synovial Membrane The synovial membrane lines the capsule

For example

On the front and above the joint, it forms a

pouch, which extends up beneath the

quadriceps femoris for three fingerbreadths

above the patella, forming the suprapatellar

bursa. This is held in position by the

attachment of the articularis genu muscle

Note: Suprapatellar bursa communicates with

the joint cavity

The synovial membrane of the knee joint forms

pouches (bursae)

To provide low-friction surfaces for the

movement of tendons associated with the joint

Some bursae communicate with the joint cavity

and some do not normally communicate

Articularis

genu

Note:

Suprapatellar

bursa Consequently, abrasions or

penetrating wounds (e.g stab

wounds) superior to the patella

may result in suprapatellar

bursitis caused by bacteria

entering the bursa from the torn

skin. The infection may spread

to the knee joint

The prepatellar bursa lies in the

subcutaneous tissue between the

skin and the patella

Prepatellar bursitis

(housemaid’s knee)

Is usually a friction bursitis caused

by friction between the skin and

patella

Prepatellar

bursa

Subcutaneous infrapatellar

bursitis results from

excessive friction between the

skin and tibial tuberosity

Subcutaneous

infrapatellar

bursa

The superficial infrapatellar

bursa lies in the subcutaneous

tissue between the skin and the

ligamentum patellae

Deep

infrapatellar

bursa

The deep infrapatellar bursa

lies between the ligamentum

patellae and the tibia

Infrapatellar fat pad

Bursae are found wherever skin,

muscle, or tendon rubs against

bone. Four are situated in front of

the joint and the rest are found

behind the joint

The other bursae are found related to the

tendon of insertion of the biceps femoris;

related to the tendons of the sartorius,

gracilis, and semitendinosus muscles as

they pass to their insertion on the tibia;

beneath the lateral head of origin of the

gastrocnemius muscle; and beneath the

medial head of origin of the

gastrocnemius muscle, beneath thhe

iliotibial tract

Subtendinous

bursa of biceps

femoris

Anserinus

bursa

The popliteal bursa is

found between the tendon of

popliteus and the lateral

condyle of tibia and

communicates with the joint

cavity.

The cruciate ligaments lie behind the synovial cavity and are not bathed in

synovial fluid.

Locking mechanism

When standing the knee joint is locked into

position, thereby reducing the amount of muscle

work needed to maintain the standing position

Locking mechanism has 3 components:

1- The change in the shape and size of the

femoral articular surfaces

2- The medial rotation of the femur on the

tibia during extension

Medial rotation and full extension tightens all

the associated ligaments

3- The body’s center of gravity is positioned

along vertical line that passes anterior to the

knee joint

Keeps the knee extended when standing

Note

The joint surfaces become larger and more stable in extension

The extended knee is

said to be in the

locked position

The knee joint can not be flexed

unless it is unlocked by the

popletius

Before flexion of the knee can occur, it is

essential that the major ligaments

Be untwisted/ slackened to permit movements

between the joint surfaces

This unlocking or untwisting process is

accomplished by the popliteus muscle

Which laterally rotates the femur on tibia

Popliteus

Origin: lateral surface of

lateral condyle of femur by

a rounded tendon

Insertion: posterior surface

of tibia above soleal line

Nerve supply: Tibial nerve

Action: flexes leg at knee

joint, unlocks the extended

knee at the initiation of

flexion by lateral rotation

of femur on tibia (when

the foot is on the ground)

and slackens ligaments of

knee joint

Medial rotates the tibia on

the femur

Unlocking means Lateral

rotation of the femur

Or Medial rotation of the

tibia

Locking means…………..

rotation of the femur Or

…………rotation of the

tibia

Note

The popliteus arises within

the knee joint

Its tendon separates the lateral meniscus

from the lateral collateral ligament and

the capsule

It emerges through the lower part of the

posterior surface of the capsule to pass to

its insertion

Flexion

Biceps femoris, Semitendinosus, and Semimembranosus muscles,

assisted by Gracilis and Sartorius muscles

Flexion is limited by the contact of the back of the leg with the thigh

Extension

Quadriceps femoris

Extension is limited by the tension of all the major ligaments of the

joint.

Medial Rotation

Sartorius, Gracilis, and Semitendinosus

Lateral Rotation

Biceps femoris

Movements of the knee joint

The stability of the knee joint depends on the tone of the strong

muscles acting on the joint and the strength of the ligaments.

Of these factors, the tone of the muscles is the most important,

and it is the job of the physiotherapist to build up the strength

of these muscles, especially the quadriceps femoris, after injury

to the knee joint.

Femoral, obturator,

common fibular and tibial

nerves

Femoral, popliteal, lateral

circumflex femoral arteries

Nerve supply of the knee joint

Blood supply of the knee joint

Tibial collateral

ligament extends from

medial epicondyle of

femur to medial aspect

of tibia

The tibial collateral

ligament prevents lateral

displacement

(abduction) of tibia

under femur

The medial collateral ligament

is firmly attached to the capsule

and medial meniscus

The 3 most commonly injured

structures at the knee are:

Tibial collateral ligament

Medial meniscus

ACL

The terrible or

Unhappy triad

Usually results from a blow to the

lateral aspect of the knee with the

foot on the ground

Knee joint and menisci from above

ACL and PCL attachment points

Prepatellar bursitis

(housemaid’s knee)

Lateral collateral ligament: isolated from knee joint

Note: it is cord-like

Medial collateral ligament: isolated from knee joint

Note: it is flat

Patellar tendon

rupture:

Sagittal

radiograph

Suprapatellar bursa

Quadriceps tendon

Patellar ligament

Femur

Tibia

Patella

Fibula

Lateral meniscus

MRI of the Knee (Sagittal View)

MRI of the Knee

(Coronal View)

Femur

Tibia

Lateral

meniscus Medial meniscus

ACL

PCL