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APK 3220c Biomechanical Basis of Movement > Knee Joint Complex > Flashcards

Knee Joint Complex Flashcards

1
Q

Medial Angle

A

175-185 degrees normally
1. Greater than 185 is genu valgum, knock knees, high lateral compressive forces; Increases force on lateral
condyle
2. Less than 175 is genu varum, bow legged, high medial compressive force; Increases force on medial
condyle
3. Abnormal tibiofemoral alignment- as measured by this angle alters compressive and tensile forces at the knee. May lead to frontal plane knee laxity b/c of articular cartilage degeneration (OA).

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2
Q

ACL Tear

A

High injury rate- most commonly torn in knee flexion
with valgus positioning and tibial rotation in either direction
Commonly torn when ACL wraps around PCL with lateral femoral rotation (open chain: medial tibial rotation)
Commonly torn when ACL wraps around the lateral femoral condyle with medial femoral rotation (open chain: lateral tibial rotation)

Also torn in Knee hyperextension (ACL resists this)

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3
Q

Knee Flexion

A

Primary: Semimembranosis, Semitendonosis, Biceps Femoris
Secondary: Sartorius, Gracialis, Popliteus, Gastrocnemius

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4
Q

Normal Hyperextension at the knee

A

5-10 degrees

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5
Q

Genu Recurvatum

A

More than 10 degrees of hyperextension; pathologic hyperextension of the knee especially seen during
gait which of repeated loading can damage the posterior capsular ligaments

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6
Q

Knee Extension

A 
Primary Muscles: 
   Vastus Lateralis
   Vastus Medialis
   Vastus Intermedius
   Rectus Femoris
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7
Q

Lateral Rotation

A

Biceps Femoris

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8
Q

Medial Rotation

A

Semimembranosis, Semitendinosus, Sartorius, Gracilis, Popliteus

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9
Q

Pes anserinus

A

semitendinosus, gracilis, sartorius

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10
Q

Hamstrings

A

Prevent Anterior Translation of Tibia; Dynamic Restraint

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11
Q

Popliteus, Patella/Quadriceps

A

Prevents Posterior Translation of Tibia; Dynamic Restraints

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12
Q

MCL

A

• Runs from medial aspect of femoral condyle to medial aspect of proximal tibia
• Taut in extension and resists hyperextension
• Resists valgus stress (increasingly so with knee flexion)
• Checks lateral rotation of the tibia
• Back up restraint (when ACL is deficient) in preventing anterior
translation of the tibia

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13
Q

LCL

A

• Strong cord like
• Runs from lateral femoral condyle to head of fibula
• Taut in extension and resists hyperextension
• Resists varus stress
• Resists lateral rotation of the tibia (most prominently at
35 degrees of flexion)
• Resist combined lateral rotation posterior translation of
the tibia

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14
Q

Genu varum

A

Increases compressive force on medial

condyle; tension on LCL, compression on MCL

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15
Q

Genu Valgum

A

Increases compressive force on lateral

condyle; tension on MCL, compression on LCL

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16
Q

ACL

A

Primary restraint for anterior translation of the tibia

Stability functions
1. Prevents anterior translation of the tibia with respect to the femur
2. Prevents hyperextension
3. Secondary stabilizer (alongside MCL) in
resisting valgus loads
4. Plays a role also in resisting valgus
stress

17
Q

PCL

A

Primary restraint to posterior
displacement of tibia

Also helps resist varus and
valgus stresses

18
Q

Oblique Popliteal Ligament

A

Joint capsule reinforced by tendinous expansion of the semimembranosus muscle
• Runs from posterior to the tibial medial condyle to central part of the posterior aspect of the joint capsule
• Resists valgus stress in full knee extension

19
Q

Arcuate Ligament

A

Runs from fibula head to intercondylar area of the tibia and to the lateral
epicondyle of the femur
• Resists Varus stress in full knee extension

20
Q

Both Oblique Popliteal Ligament and Arcuate Ligament

A

• Both are taut in extension and prevent hyperextension

21
Q

Knee Flexion

A

0-25 degrees of flexion rolling occurs, after that a combination of rolling and
gliding take place (posterior roll and anterior glide).

ACL and posterior wedge-shaped portions of menisci mediates posterior roll and anterior glide

22
Q

Knee Extension

A

PCL and anterior portions of mensici mediates anterior roll and posterior glide

23
Q

Axial Rotation

A

Accessible ONLY in knee FLEXION (greatest at 90 degrees of
flexion)
• Range of Motion: 60-70 degrees
• Distinct from screw of mechanism as it accessible but not obligatory
• Due to joint laxity and incongruence
• Center of rotation – medial intercondylar tubercle of the tibia

24
Q

Resisting knee valgus stress (knee abduction

moment)

A

muscles of the pes anserinus (semitendinosus, gracilis, sartorius) in flexion

25
Q

Resisting knee varus stress (knee adduction

moment)

A
  • Iliotibia tract
  • Biceps tendon
  • Popliteus tendon
26
Q

Medial/Lateral Rotation is maximized at 90 degrees of knee flexion

A

True

27
Q

Screw Home Mechanism

A

• Referred to as the locking of the knee
• Most evident in last 5° of extension
• Caused mainly by asymmetry in medial and
lateral femoral condyles;
OBLIGATORY, OCCURS PASSIVELY/AUTOMATICALLY AS YOU GO INTO KNEE EXTENSION
At about 30° of flexion, the shorter lateral condyle
completes its rolling and gliding.
As extension continues, the longer medial condyle
continues to roll anteriorly and glide posteriorly. This
causes medial rotation of the femur on tibia about the
fixed lateral condyle
Ligaments (especially the cruciate ligaments- ACL) are
tensioned and may contribute to this obligatory
movement

28
Q

Unlocking the Knee

A

• To initiate flexion, the medially rotated
femur must laterally rotate (closed
chain
• To initiate flexion, the laterally rotated
tibia must medially rotate (open chain)
• Assisted via activation of the popliteus
muscle
• Unlocking will still occur in passive
flexion
Voluntary- we can actively do it (VOLITIONAL); DOF we can voluntarily control

29
Q

Lateral Rotation/Medial Rotation of Knee

A

Achieved when knee is flexed 90 degrees

30
Q

Knee Joint Movement:

Axial Rotation

A

• Accessible only in knee flexion (greatest at 90 degrees of
flexion)
• Range of Motion: 60-70 degrees
• Distinct from screw of mechanism as it accessible but not
obligatory
• Due to joint laxity and incongruence
• Center of rotation – medial intercondylar tubercle of the
tibia

31
Q

Knee Joint Movement:

Axial Rotation

A

• Accessible only in knee flexion (greatest at 90 degrees of
flexion)
• Range of Motion: 60-70 degrees
• Distinct from screw of mechanism as it accessible but not
obligatory
• Due to joint laxity and incongruence
• Center of rotation – medial intercondylar tubercle of the
tibia

32
Q

Medial Rotation

A

Open chain- Anterior gliding of the lateral femoral condyle on the tibia

33
Q

Dynamic Restraints to Knee Valgus Stress

A

Muscle of pes anserinus in Knee flexion

34
Q

Dynamic Restraints to Knee Varus Stress

A

Iliotibia Tract
Biceps Tendon
Popliteus Tendon

APK 3220c Biomechanical Basis of Movement (8 decks)

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