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Knee Flashcards

1
Q

Distal Femur

A

Lateral/medial condyles

Intercondylar notch/groove - separates condyles posteriorly - cruciate ligaments travel through

Knee joint - tibiofemoral and patella-femoral joint

Condyles are continuous anteriorly

Medial condyle travels little further distally than does lateral condyle

Tibia sits more horizontal - puts femur in angle

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2
Q

Tibial Articulation

A

Lateral/medial tibial plateaus and condyles

Medial has a larger surface area (allows the femur to go more anteriorly)

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3
Q

Patella

A

Sesamoid bone

Base superiorly, apex inferiorly

Anterior surface - convex in all directions

Posterior surface - covered by articular cartilage

Embedded in the quad tendon

Articular surface inserts w/ intercondylar groover

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4
Q

Patella Functions - Primary Function

A

Increase angle of application (moment arm of quads)

Look at CoR - patella increases the moment arm

Remove patella - lose MA

Lengthens quads - on slack

Position of active insufficiency when patella is removed (muscle contracts so much - can’t extend knee)

Stand in ext - least force from quads

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5
Q

Patella Functions - Secondary Function

A

Protect quads tendon from excessive friction

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6
Q

Normal Alignment

A

Shaft of femur slightly medial

Medial condyle is longer, which is why shaft toward midline is longer

Normally sit in valgus - tibia going away in midline

Genu valgum and varus - frontal plane angles

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7
Q

Genu Valgum

A

Slight - normal

Angle is <170 degrees is excessive

Knock kneed

Knee femur closer together, tibia further apart

M/L jt line - symmetrical

Medical surface is further away (unweighting medial jt line) and lateral is closer together (closing down on lateral jt line - more force)

Static valgum - standing up straight

Dynamic algum - go into this position w/ mvt

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8
Q

Genu Varum

A

Angle is greater than 180 degrees is excessive

Bow leg

Anything beyond straight

Abnormal

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9
Q

Joint Capsule

A

Large, complexly attached and lax w/ several recesses

Reinforced posteriorly by muscles and popliteal ligaments, M/L by collateral ligaments

Vastus medals and vastus lateralis, MPFL (medial patella femoral ligament), retinacula anteriorly

Ligamens, fascia, muscle that reinforce knee capsule

Provides stability to joint

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10
Q

Menisci

A

Crescent shaped, fibrocartilaginous discs

Medial is semicircular, lateral is circular

Thick peripherally, thin centrally

Blood supply greatest in periphery

Receives blood flow from papillary vessels and synovial membrane (red red zone, red white zone, white white zone)

Anterior and posterior horns anchor at the end

Secondary attachments - quads (bilaterally), semimembranosus (bilaterally), popliteus to lateral only

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11
Q

Menisci - Functions

A

Primary function - reduce compressive stress, stabilize jt during motion

Secondary function - lubricate articular cartilage, proprioception, guide arthrokinematics

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12
Q

Osteokinematics

A

2 DOF

Flex/ext in sagittal plane - M/L AoR (migrating)

IR/ER in horizontal plane (if knee is slightly flexed)

Flex - 0 to 135 degrees

Ext - 0 to 15 degrees

IR - 20 to 30 degrees

ER - 30 to 40 degrees

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13
Q

Coupled Motion

A

Flex/ext don’t occur as pure sagittal plane motions

Axis is oblique

Tibia moves from position of slightly lateral to femur to slightly medial to femur in full flex

One motion occurs, obligatory second motion occurs

At knee jt, coupled motion b/c transverse/sagittal plane motion

As tibia flexes/extends, coupled IR/Er of tibia occurring (extend - tib tub moved laterally - ER) (bend knee - rotate back in - IR)

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14
Q

Tibia IR/ER

A

Axial rotation - longitudinal/vertical AoR

Increases w/ knee flex

90 degrees of knee flex, 40-45 degrees total of axial rotation

ER: when tibial tuberosity lateral to anterior distal femur

Available ROM increase w/ knee flex

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15
Q

Arthrokinematics - Extension

A

Tibia (concave) on femur (convex) - tibia rolls and glides anteriorly

Femur on tibia - femoral condyles roll anteriorly and glide posteriorly

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16
Q

Arthrokinematics - Flexion

A

Opposite of extension

Tibia on femur - rolls and glides posteriorly

Femur on tibia - femoral condyles roll posteriorly and glide anteriorly

Tibia must 1st IR to unlock when going from ext to flex

Tibia on femur - popliteus initiates tibial IR

Femur on tibia - popliteus initiates femoral ER

Femoral IR results in sane mvt as tibial ER

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17
Q

Screw Home (Locking) Mechanism

A

Obligatory ER of tibia during TKE (not voluntary or produced muscular forces)

Jt arthrology dictates arthrokinematics during final 30 degree KE

Flex force “unlocks” by medially rotating

Medial epicondyle of tibia extends further than lateral epicondyle (femur/tibia gliding, medial femur is going to extend more anteriorly - medial concavity is deeper)

Dictated by size of medial epicondyle

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18
Q

Ligaments

A

Collateral - primarily provide frontal plane stability against varus/valgus force (MCL/LCL)

Cruciate - provide multiplanar stability @ knee (ACL/PCL)

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19
Q

MCL

A

Resists valgus stresses (reinforces capsule)

  • At full ext, 57% of restraining force
  • At 25 degrees of flex, 78% of restraining force

Secondary role in preventing anterior translation (may place increased stress on ACL if injured)

Vascularized - capacity to heal

Does more w/ slightly knee flexed than extended

More commonly injured structures

20
Q

LCL

A

Resists varus stresses

At 5 degrees of flexion accounts for 55% of restraining force

At 25 degree knee flex accounts for 69% of restraining force

Resist more various forces when knee is slightly flexed

21
Q

Cruciate (ACL/PCL)

A

Named for their attachments to the tibia

Together, multiplayer stability of knee, mostly in sagittal plane (b/c they cross)

Guide arthrokinematics

Contributes to proprioception

Both together prevent rotation

22
Q

ACL

A

Runs from anterior tibial plateau to lateral femoral condyles - crosses joint diagonally

Primary restraint - anterior displacement of tibia on femoral condyles

Two bands wrap around each other: anteriomedial (AMB) and posterolateral (PLB)

Most fibers taut w/ knee close to full ext

Forceful contraction of quads - ACL pulls tib tub and translate tibia anteriorly (guide arthrokinematics)

Most commonly injured when knee is slightly flexed and tibia rotated in either direction

  • Contact: external force
  • Non-contact: change of direction, quick pivoting, more ACL tears

Forceful contraction of quads pulls tibia anteriorly, so can strain ACL esp near full ext

When we flex knee and in valgus - ER of tibia occurring
-Quads turn on to extend the knee - why patients tear ACL in this position

23
Q

PCL

A

Runs from posterior intercondylar area of tibia to medial femoral condyle

Primary restraint - posterior displacement of tibia on femoral condyles (or anterior displacement of femur on tibia in closed chain)

Also has 2 bands: posteromedial bundle (PMB) and anterolateral bundle (ALB)

Majority of fibers remain taut thru/out flex/ext but most taut w/ greater flex

Contraction of hamstring can slide tib/fib posterior

PCL can check posterior translation arthrokinematics

Most injuries - contact (trauma, football, MVA)

24
Q

Flex/Ext with ACL/PCL

A

Flexion - PCL taut, ACL slack

Extension - ACL taut, PCL slack

25
Patellofemoral Joint
Interface b/w patella and intercondylar groove As knee flexes and extends, slides over intercondylar groover Max contact: only 30% of total surface Extend knee - many angles of forces are coming to guid and track patella into groove As knee flexes, patella moves down As knee extends, patella moves up
26
Motions of Patella
M/L tilt and M/L rotation Reference rotation off inferior aspect of patella
27
Q-Angle
ASIS to mid-patella Tib tub to mid-patella Approx. 15 degrees in women Approx. 11 degrees in men >15 degrees - abnormal Wider ASIS - larger Q-angle Huge Q-angle - bowstring of patella (quads pulling patella laterally)
28
PF Joint Kinetics
Resultant force based on concurrent forces (quads and patellar tendn) - summative force toward knee joint Knees far in front of toes - resultant force is greater Squatting w/ bad mechanics can cause knee pain - increased forces on patello-femoral joint
29
Extensors
Quads Efficiency affected by patella Creates force 2/3 greater than hamstrings, max torque at mid range (40-70 degrees flex) Dampens impact loading (esp during high impact losing, such as landing from jump, running, descending from high step) Accelerates tibia or femur for tasks requiring knee ext Eccentrically - quads control rate of descent of body's CoM, such as sitting/stooping; shock absorber for knee; controls flexion
30
Tibial on Femoral External MA
External MA increases from 90 to 0 degrees of knee flexion External MA during knee ext - greater Gravity has gained an advantage when going thru this mvt - why parents feel like it's harder to move to knee ext
31
Quadriceps Lag
To complete last 15 degrees of knee ext, 60% increase in force of quads muscles is required Lag - quads are not strong enough to fully extend knee (TKE)
32
Femoral on Tibial External MA
External MA decreases from 90 to 0 degrees of flexion Line of force anterior to jt - quads don't need to do work to extend knee (ext moment) Bending - external MA gets larger - gravity takes over
33
Flexors/Rotators - Hamstrings
Most active during walking/running Accelerate/decelerate tibia during tibia on femur mets Stabilizer in femur on tibial mvts Max torque development near full knee ext
34
Flexors/Rotators - Sartorius/Gracilis
Pes anserine provides medial stability and functions to IR tibia
35
Flexors/Rotators - Popliteus
IR and flexor "Unlocks" knee
36
Abnormal Patella
Patella squinting - knees in Patella frog eye - knees out
37
Patella Alta and Baja
Alta - higher Baja - lower than normal
38
Genu Recurvatum
Hyperext of knees
39
Baker's/Popliteal Cyst
Fluid pools in posterior aspect of knee
40
Valgus Stress Test
Purpose: to screen for one-plane medial instability at knee (MCL) Procedures: pt supine, examiner applied valgus force at knee w/ ankle in slight lateral rotation, test performed in full knee ext and w/ knee flexed 20-30 degrees Positive - gapping of tibia away from femur, pain in MCL Positive w/ knee flexed - more likely an indication of one-plane instability (MCL, post oblique ligament, PCL, capsule) Positive w/ knee extended - major disruption and will likely find pos rotatory instability tests (MCL, PCL, ACL, capsule, M quad expansion, semimem) Negative - no gapping or pain
41
Varus Stress Test
Purpose: to screen for one-plane lateral instability at knee (LCL) Procedure: pt supine, examiner applied varus force at knee w/ ankle in stabilized, test performed in full knee ext and w/ knee flexed 20-30 degrees Positive - gapping of tibia away from femur, pain at LCL Positive w/ knee flexed - more likely an indication of one-plane instability (LCL, capsule, ITB, biceps fem tendon, arcuate-popliteus complex) Positive w/ knee extended - major instability and will likely find pos rotatory instability tests (LCL, capsule, ITB, biceps fem tendon, arcuate-popliteus complex, PCL, ACL, lateral gastroc) Negative - no gapping or pain
42
Lachman Test
Purpose: screen for one-plane anterior instability at knee (ACL) Procedure: pt supine w/ knee flex b/w 0 and 30 degrees, examiner stabilize distal femur w/ outside hand and anteriorly translates proximal tibia w/ inside hand Positive - mushy/soft end feel, excessive displacement/gapping Negative - normal end feel, no excessive motion
43
McMurray Test
Purpose - screen for medial and lateral meniscal injury Procedure - pt supine with knee fully flexed, examiner passively IR tibia and maintains position while extending knee (lateral meniscus), then ER tibia and extend knee (medial meniscus) Positive - clunk, snap, click, accompanied by pain that occurs b/w full flex and 90 degrees of flexion Negative - painfree and smooth motion
44
Apley's Test
Purpose - screen for medial and lateral meniscal injury Procedure - pt prone w/ knee flexed at 90 degrees, examiner stabilize pt's thigh using own knee, examiner M/L rotates tibia, combined w/ distraction (distal tib-fib) and repeated w/ compression Positive - restriction, excessive mvt or discomfort w/ compression, pain/hypermobility w/ distraction is more likely associated w/ ligamentous injury Negative - no pain, restriction or excessive motion w/ compression or distraction
45
Clarke's Sign (Patellar Grind Test)
Purpose - screen for retropatellar dysfunction Procedure - pt supin w/ knee ext, examiner gently uses web of hand to press down just prox to pole of patella, w/ pressure sustained, pt performs quad set Postive - pain/grinding during quad contraction

Kinesiology (5 decks)

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