Knee ComplexKnee Complex

• Consists of two distinct articulations namelyConsists of two distinct articulations namely

1.1. Tibiofemoral jointTibiofemoral joint

2.2. Patellofemoral jointPatellofemoral joint• In closed kinematic chain it works in In closed kinematic chain it works in

conjunction with hip & ankle to support body conjunction with hip & ankle to support body weight in static erect postureweight in static erect posture

• In open kinematic chain knee provides In open kinematic chain knee provides mobility for the foot in spacemobility for the foot in space

Tibiofemoral Joint:Tibiofemoral Joint:• Double condyloid joint with 2Double condyloid joint with 2 freedom of freedom of

motionmotion• Flexion/extension occur in saggital plane Flexion/extension occur in saggital plane

about a coronal axis about a coronal axis • Medial/lateral rotation occur in transverse Medial/lateral rotation occur in transverse

plane about a vertical axisplane about a vertical axisFemoral articular surface:Femoral articular surface:• consists of lateral and medial condyles and consists of lateral and medial condyles and

an intercondylar notchan intercondylar notch• medial condyle is slightly longer than the medial condyle is slightly longer than the

lateral onelateral one

Tibial articular surface:Tibial articular surface:• consists of two concave asymmetrical consists of two concave asymmetrical

medial and lateral condylesmedial and lateral condyles• medial tibial articulating surface is 50% medial tibial articulating surface is 50%

larger than the lateral onelarger than the lateral one• two tibial condyles are separated by a two tibial condyles are separated by a

roughened area and two bony spines called roughened area and two bony spines called as intercondylar tuberclesas intercondylar tubercles

• these tubercles become lodged in the these tubercles become lodged in the intercondylar notch of femur during knee intercondylar notch of femur during knee extensionextension

Articulation:Articulation:• When condyles of femur are placed on tibial When condyles of femur are placed on tibial

condyles an incongruence developscondyles an incongruence develops• Accessory joint structure Accessory joint structure menisci menisci are present to are present to

develop the congruencydevelop the congruencyMenisci:Menisci:• Asymmetrical fibrocartilage joint disksAsymmetrical fibrocartilage joint disks• Medial is semicircle and lateral is four-fifths of a Medial is semicircle and lateral is four-fifths of a

ringring• Both are open towards the intercondylar area,thick Both are open towards the intercondylar area,thick

centrally,forming concavitiescentrally,forming concavities• Wedge shaped menisci increase radius of Wedge shaped menisci increase radius of

curvature of tibial condyles and there fore joint curvature of tibial condyles and there fore joint congruency congruency

• Also play an important role in distributing Also play an important role in distributing weight bearing forces,reducing friction and weight bearing forces,reducing friction and serve as shock absorbersserve as shock absorbers

• Menisci are attached around its periphery to Menisci are attached around its periphery to tibial condyle by coronary ligamenttibial condyle by coronary ligament

• Anterior horns are joined to each other by Anterior horns are joined to each other by transverse ligamenttransverse ligament

• Menisci are rich with free nerve endings Menisci are rich with free nerve endings and three different mechanoreceptors and and three different mechanoreceptors and hence act as a source of information about hence act as a source of information about joint position, direction of movement and joint position, direction of movement and velocity of movementvelocity of movement

• Menisci are important in distributing and Menisci are important in distributing and absorbing large forces crossing the knee absorbing large forces crossing the knee jointjoint

• Ordinarily compressive forces in the Ordinarily compressive forces in the dynamic knee may reach 2-3 times body dynamic knee may reach 2-3 times body weight in normal gait and 5-6 times in weight in normal gait and 5-6 times in activities such as running and stair climbingactivities such as running and stair climbing

• Menisci assume 40% – 60% of the imposed Menisci assume 40% – 60% of the imposed loadload

Tibiofemoral alignment & weight bearingTibiofemoral alignment & weight bearingforces:forces:• Anatomic axis of femur is oblique directed Anatomic axis of femur is oblique directed

inferiorly and medially from proximal to inferiorly and medially from proximal to distal enddistal end

• Anatomic axis of tibia is also directed Anatomic axis of tibia is also directed almost verticallyalmost vertically

• Both axes normally form an angle medially Both axes normally form an angle medially at knee of 185at knee of 185-190-190,femur is angulated off ,femur is angulated off vertical 5vertical 5 -10 -10 creating a normal valgus creating a normal valgus angle at kneeangle at knee

• Mechanical axis of lower limb is weight Mechanical axis of lower limb is weight bearing line from center of head of femur to bearing line from center of head of femur to superior surface of head of talussuperior surface of head of talus

• Because weight bearing line follows Because weight bearing line follows mechanical rather than anatomic axes, the mechanical rather than anatomic axes, the weight bearing stresses on the knee in weight bearing stresses on the knee in bilateral stance are equally distributed bilateral stance are equally distributed between medial and lateral condylesbetween medial and lateral condyles

• Deviations in normal force distribution may Deviations in normal force distribution may be caused by an increase or decrease in be caused by an increase or decrease in normal tibiofemoral angle normal tibiofemoral angle

• If medial angle is greater than 195If medial angle is greater than 195 - -Genu Valgum Genu Valgum (knock knees)(knock knees)

• This will increase compressive force on This will increase compressive force on lateral condyle while increasing tensile lateral condyle while increasing tensile stresses on medial structuresstresses on medial structures

• If medial angle is 180If medial angle is 180 or less - or less -

Genu Varum Genu Varum (bow knees)(bow knees)• This will increase compressive forces on This will increase compressive forces on

medial condyle while increasing tensile medial condyle while increasing tensile stresses on lateral structuresstresses on lateral structures

• Constant overloading of stresses result in Constant overloading of stresses result in damage to cartilagedamage to cartilage