Knee Flashcards by Armi B

Knee joint is a ——axial joint with ——-degrees of freedom.

biaxial

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Knee joint has 2 articulations

Tibiofemoral articulation

Patellofemoral articulation

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Knee joint is what type of joint?

this is a test question

Ginglymus joint (a joint that allows movement in but one plane, forward and backward, as does a door hinge) A hinge joint`

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Does fibula contribute in the knee joint?

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Sagittal plane motion provided by an axis

which passes through the femoral condyles located parallel to the frontal and transverse planes

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What allows the knee to be aligned so that purely sagittal plane motion occurs?

changes in angle of inclination

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The varus attitude of the femur is balanced by

the longer/larger medial femoral condyle to put the axis of the joint parallel to the transverse plane

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Axes of the knee

The axis providing sagittal plane motion
The anatomical axis of the femur and tibia
The mechanical axis of the knee

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The anatomic axes of the femur and tibia are their ———axes

Longitudinal

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Longitudinal axes of femur and tibia form an angle of

185º-190º (5-10 degrees off of vertical)

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The tibia is relatively———–on the femur

Abducted

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tibia has a physiological valgus of

5-10º

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Mechanical axis (weight-bearing line) of the knee joint normally passes

through the centers of the knee , hip and ankle joints

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Mechanical axis forms an angle of ~

3º from the vertical

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The mechanical axis represents the line through which

ground reactive forces passes

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what happens if frontal plane angulation at the knee increases ( genu varum or genu valgum

The mechanical axis will no longer pass through the center of the knee joint

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What does the mechanical axis represent?

It represents the path for ground reactive forces

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if the mechanical axis falls medial to the knee , the condition is called

Genu Varum

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In genu Varum, compressive forces will be ————– and ————-

increased medially

decreased laterally

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If the mechanical axis falls laterally to the knee joint, it is called

Genu valgum

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in Genu valgum

compressive forces will be increased laterally and decreased medially

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A change in the mechanical axis of the knee will cause

a change in the ground reactive forces (external moment) across the knee.

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constant overloading on the increased compression side of the knee may lead to

articular cartilage damage
increased frontal plane deformity
increased overload

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foot orthoses changes

the mechanical axis

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external moment examples

GRF Gravity Momentum

internal moment examples

muscles ligaments bony limitation

GRF causing ---------------------and the body responding with ------------

External abduction moment | Internal adduction moment

Requirements for Knee joint function

1. Great mobility | 2. Stability

Knee joint flexibility is provided by

- Anatomical structure of the knee | - The instant axis of rotation of the tibiofemoral articulation

The change in location of instant axis of rotation is a result of

combination of gliding and rolling

Flexion of the knee from full extension to 25º flexion is purely-------

rolling

Flexion beyond 25º requires

Anterior gliding | posterior rolling of the femur on the tibia to prevent the femur from falling off the tibia posteriorly

the gliding motion during knee FLEXION is facilitated by

ACL | menisci

Knee EXTENSION is facilitated by

PCL | Menisci

As the knee flexes , the femur

slides forward on the tibia

What is the normal max motion of the tibiofemoral articulation in the sagittal plane?

140º of flexion | 5-10º of extension (hyperextension)

Hyperextension greater than---------is generally considered genu recurvatum

10º

minimum requirements for Sagittal plane knee motion in gait

60º of knee flexion ( on level ground)

minimum requirements for Sagittal plane knee motion in stair climbing

80º of knee flexion

minimum requirements for Sagittal plane knee motion in sitting

90º of knee flexion

In stance phase of the gait, the greatest amount of force is on

the medial plateau

In swing phase of the gait, the greatest amount of force is on

the lateral plateau

which one is larger? medial or lateral plateau?

Medial plateau is 50% larger and has cartilage 3X thicker than the lateral plateau

Hip and ankle position will effect sagittal plane knee RANGE OF MOTION in

OKC

Hip and ankle position will effect KNEE FUNCTION in

CKC

Transverse plane knee motion occurs via 2 separate mechanisms :

- true transverse plane knee motion | - the screw-home mechanism

How much true transverse plane knee motion occurs depends on

sagittal plane position of the knee

Fully extended knee

has no transverse plane motion due to interlocking mechanism between femoral and tibial condyles

When there is no transverse plane motion due to interlocking mechanism between femoral and tibial condyles this represents

closed-packed or locked position of the knee joint and the knee ligaments

When the knee is flexed at 90º, the ligaments are

lax

When the knee is flexed at 90º. external rotation may be as high as

45º

When the knee is flexed at 90º, internal rotation may be as high as

30º

As the knee moves further away from 90º in the direction of extension/flexion the amount of transverse plane motion available

decreases

Screw-Home mechanism occurs as a result of

The medial condyle being 1.7 cm longer than the lateral condyle which allows for spiral like motion to occur

in Screw-Home mechanism, what you see is

The tibia appears to externally rotate on the femur with knee extension

in Screw-Home mechanism, what actually happens is

the femur internally rotates relative to the tibia | this is most notable during the last 5º of knee extension

Screw-Home mechanism is a ---------plane motion

Transverse

Screw-Home mechanism occurs with knees in what position ?

occurs with knee extension brings the knee into its closed packed position with menisci tightly interposed and the ligaments taut

Screw-Home mechanism benefits?

provides increased stability for the knee joint in the extended position

The Screw-Home mechanism sometimes referred to as

the automatic rotation of the knees

Axial or transverse plane rotations occure ----------from screw home mechanism

Separate

motion of the knees in this plane considered insignificant

Frontal plane

when the knee is flexed to about 30º we get the greatest-----------------motion

frontal plane knee motion | postion most vulnerable to frontal plane injury

frontal plane injury and anterior-posteior displacement are considered to be the result of

joint incongruity and variable amounts of ligamentous laxity

stability of the knee is primarily provided by soft tissue structures

menisci | ligaments

menisci increase

concavities of the tibial surfaces upon which the femoral condyles sit

menisci act to improve

joint congruity for a joint whose bony structure is relatively incongruous

menisci reduce

friction

menisci distribute

weight bearing forces

Ligaments resist or control

- Excessive knee extension - Varus or Valgus stresses at the knee - Anterior or posterior displacement of the tibia beneath the femur - medial or lateral rotation of tibia beneath the femur - combinations of A/P displacements and rotations of the tibia (rotatory stablization )

When the knee is FULLY EXTENDED which articular facets of the femur articulate with the patella ?

Both medial and lateral articular facets

When the knee flexes past 90º which articular facets of the femur articulate with the patella?

Only the medial facet articulates with the patella

Patella helps to improve lever arm of

the quadriceps femoris

absent patella

decreased strength from the quads b/c you lost some of the lever arms

patella aids in Knee

Extension

How does the patella help in knee extension?

by lengthening the lever arm of the quadriceps femoris

Patella allows for better distribution of

compression stresses on the femur by increasing the contact between the patella and femur

Increased knee flexion will increase

the force of the quadriceps contraction

increase in the force of the quadriceps contraction

increases the force on the patellofemoral joint

patella as it glides in the intercondylar area adjusts

the angle of insertion of the quadriceps femoris into the tibia to conform the long axis of the leg

Q-angle

represents the angle of the pull of the quadriceps femoris- a vertical line from ASIS to the border of patella to the tibial tuberosity

Q-angle is involved with what deformities?

Patella femoral pain syndrome | tracking syndrome

Increased Q-angle can cause

dislocation of the patella

Increased Q-angle is more common in female or male?

Female

Knee Flashcards

(84 cards)