Knee Joint

Objectives

Name and identify the bony features of the tibia and fibula.

Know the type and formation of knee joint.

Explain the stability factors of the knee joint.

Identify the muscles that act at the knee joint.

Know the locking and unlocking mechanism of the knee joint.

Understand the functions of the Popliteus and Iliotiabial tract.

Anterior Posterior AnteriorTransverse

condylesepicondyles

intercondylar notch

patella

tibial tuberosity

tibial plateaus

Tibia: Condyles (plateaus)Tibial tuberosity

Tibia and fibulaare united by aninterosseous Membrane.[Proximal and distal tibio-fibular jts]

The fibula is not part of the knee joint.

Anterior.Sagittal section thru knee

Patella articulateswith the femur.

interosseous membrane

Head of Fibula

During the entirerange of kneeflexion, the patellaonly articulates with the femur.

KNEE:

Modified hinge jt.-flexion / extension (some rotation)

Superior view of tibial surface.

Medial and lateral articularsurfaces, separated by an intercondylar eminence.

Medial and lateral Menisci:

Fibrocartilage shock-absorbersthat sit on surface of tibial condyles and deepen the articular surface.

Anterior and posterior Cruciate ligaments (ACL, PCL):-hold femur and tibia together-stabilize knee joint

lateral articular surface

medial articular surface

intercondylar eminence

lateral meniscus PCL medial meniscus

ACL

Tibial Condyles Tibial Condyles

Medial and lateralfemoral condyleshave same shape as correspondingtibial condyles:

Medial – elongatedLateral – circular

Meniscii:Each is attached to tibia at their ends (horns),and outer periphery(coronary lig.)

Femur

Type & Articular Surfaces

Knee joint is formed of:Three bones.Three articulations.Femoro-tibial articulation: between the 2 femoral condyles & upper surfaces of the 2 tibial condyles (Type: synovial, modified hinge).Femoro-patellar articulation: between posterior surface of patella & patellar surface of femur (Type: synovial, plane).

Capsule

Deficient anteriorly & is replaced by: quadriceps femoris tendon, patella & ligamentum patellae.Possesses 2 openings: one (posteriorly) for popliteus tendon & one (anteriorly) for communication with suprapatellar bursa.

Menisci They are 2 C-shaped

plates of fibro-cartilage attached by anterior & posterior horns, to the articular surface of tibia.

FUNCTION: Deepen articular

surfaces of tibial condyles.

Serve as cushions between tibia & femur.

Lateral meniscus

Medial meniscus

Size small LargeShape Circular OvalOuter border separated from lateral collateral

ligament by popliteal tendon.attached to the capsule & medial collateral ligament.

Mobility More mobile Less mobile Liablity for injury

Less liable More liable

The synovial membrane1- lines the capsule,2- attaches to the margins of

the articular surfaces,3- attaches to the peripheral

edges of the menisci (semilunar cartilages),

4- covers the front of the ant. cruciate ligament, and the back of posterior cruciate ligament.

5- communicates with: - suprapatellar bursa, - popliteus bursa, - semimembranosus

burse, - gastrocnemius bursa.

Bursae Related to Knee1. Suprapatellar bursa: between

femur & quadriceps tendon, communicates with synovial membrane of knee joint

2. Prepatellar bursa: between patella & skin.

3. Deep infrapatellar bursa: between tibia & ligamentum patella.

4. Subcutaneous infrapatellar bursa: between tibial tuberosity & skin.

5. Popliteal bursa: between popliteus tendon & capsule, communicates with synovial membrane of knee joint.

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Working on hands-and-knees: Housemaid knee bursasubcutaneus prepatellar bursitis.

Ligaments: 4 Extracapsular

1. Ligamentum patellae (patellar ligament): from patella to tibial tuberosity.2. Medial (tibial) collateral ligament: from medial epicondyle of femur to

upper part of medial surface of tibia (firmly attached to medial meniscus).3. Lateral (fibular) collateral ligament: from lateral epicondyle of femur to

head of fibula (separated from lateral meniscus by popliteus tendon).4. Oblique popliteal ligament: extension of semimembranosus tendon.

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Ligaments: 2 Intracapsular

The Cruciate Ligaments • Two in number,

situated in the middle of the joint.

• They are called cruciate because they cross each other

• Have received the names anterior and posterior, from the position of their attachments to the tibia.

Anterior cruciate ligament:• Extends from anterior part of

intercondylar area of tibia to posterior part of lateral condyle of femur.

• Prevents posterior displacement of femur on tibia.

• Prevents hyperextension.• Weaker of the two, slack when knee is

flexed & tightens in extension.

Posterior cruciate ligament: • Extends from posterior part of

intercondylar area of tibia to anterior part of medial condyle of femur.

• Tightens during flexion of knee joint• Prevents anterior displacement of

femur on tibia.

Stabilization of themedial knee:

Tibial collateralligament.

A flat strap whichis attached to the medial aspect of tibia and medial femoral epicondyle.

Its deeper fibres areattached to themedial meniscus.

tibial collateral ligament

Retinacularfibres

Joint capsule

Pes anserinus (goose’s foot): Common insertion ofSartorius, gracilis, semitendinosus

Movements FLEXION:

Mainly by hamstring muscles: biceps femoris , semitendinosus & semimembranosus.

Assisted by sartorius , gracilis & popliteus.

EXTENSION: Quadriceps femoris.

ACTIVE ROTATION (PERFORMED WHEN KNEE IS FLEXED):A) MEDIAL ROTATION:

Mainly by semitendinosus & semimembranosus. Assisted by sartorius & gracilis.

B) LATERAL ROTATION: Biceps femoris.

Movements

INACTIVE (DEPENDANT) ROTATION:A) LOCKING OF KNEE: Lateral rotation of tibia, at the end of extension Results mainly by tension of anterior cruciate

ligament. In locked knee, all ligaments become tight.B) UNLOCKING OF KNEE: Medial rotation of tibia, at the beginning of

flexion. Performed by popliteus to relax ligaments &

allow easy flexion.

Fibrous capsule of the KNEE (anterior):

Stabilized by: Extensor Retinacula

- Derived from insertionsof vastus lateralis andvastis medialis into patellaand into sides of patellarligament.

extensor retinacula

Vastuslateralis

Vastus medialis

Anterior knee in extension

PatellarLigament

Fibrous capsule of the KNEE (posterior):

Thickened by ligaments:

-Arcuate popliteal ligament (arching over popliteus muscle)

-Oblique popliteal ligament (from tendon of insertion of semimembranosus m.)

arcuate politeal ligament

oblique popliteal ligament

Tendon ofSemimembranosus

Popliteus

Posterior knee in extension

Structures inside the Knee joint:1- The 2 menisci

(semilunar cartilages).2- The cruciate

ligaments.3- Popliteus tendon.

Nerve supply of the knee joint:Femoral, obturator, tibial,

and common pernoneal

nerves.

Arterial supply of knee joint:From the anastomosis

around knee.

Q-Angle

The Q-angle is the angle formed by :

1-a line from the anterior superior iliac spine to the middle of the patella ,and

2-a line from the middle of the patella to the tibial tuberosity.

Males typically have Q-angles between 10 to 14o,

females between 15-17o.

Atypical Q-angles

bowleggedness

knock-knees