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USA Term 2 > Biomechanics Final *Knee* > Flashcards

Biomechanics Final *Knee* Flashcards

1
Q

What is the normal alignment of the knee in the frontal plane?

A

A slight valgus is normal

> ~20° is abnormal

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2
Q

What are excessive frontal plane deviations for the knees?

A

Excessive Genu Valgum (Knock Knee) is <~165°

Genu Varum (Bow-leg) is >~180°

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3
Q

What is Q Angle?
(Q is for Quads)

A

Another measurement of Valgus
- The Mechanical axis of the LE and combined vector of all 4 heads of the quadriceps.

(A line connecting the center of the ankle, knee, and hip. This is approximated by line parallel to patellar ligament)

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4
Q

What are normal and abnormal Q Angles?

A

Normal: 10-15°

Abnormal: More than 20°

These are important factors in Patellofemoral joint pathologies

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5
Q

What are the structures that the Anterior region of the joint capsule reinforces in connective tissue and Muscular-tendinous?

A

Connective Tissue Reinforcement :
- Patellar Tendon
- Patellar Retinacular Fibers

Muscular-Tendinous Reinforcement:
- Quadriceps

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6
Q

What are the structures that the Lateral region of the joint capsule reinforces in connective tissue and Muscular-Tendinous?

A

Connective Tissue Reinforcement :
- LCL
- Lateral Patellar Retinacular fibers
- IT band

Muscular-Tendinous Reinforcement:
- Bicep Femoris
- Tendon of Popliteus
- Lateral Head of Gastrocnemius

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7
Q

What are the structures that the Posterior region of the joint capsule reinforces in connective tissue and Muscular-Tendinous?

A

Connective Tissue Reinforcement :
- Oblique Popliteal Lig.
- Arcuate Popliteal Lig.

Muscular-Tendinous Reinforcement:
- Popliteus
- Gastrocnemius
- Hamstrings, especially semimembranosus tendon

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8
Q

What are the structures that the Posterior-Lateral region of the joint capsule reinforces in connective tissue and Muscular-Tendinous?

A

Connective Tissue Reinforcement :
- Arcuate Popliteal Lig.
- LCL
- Popliteofibular Lig.

Muscular-Tendinous Reinforcement:
- Tendon of Popliteus

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9
Q

What are the structures that the Medial region of the joint capsule reinforces in connective tissue and Muscular-Tendinous?

A

Connective Tissue Reinforcement :
- Medial Patellar Retinacular Fibers
- MCL
- Thickened Fibers posterior-medially

Muscular-Tendinous Reinforcement:
- Expansions from tendon of the semimembranosus
- Tendons of Sartorius, Gracilis, Semitendinosus (Pes Anserine)

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10
Q

What happens to the Capsule and Ligaments of the knee when the knee is in flexion and extension?

A

When the knee is in flexion the ligaments and capsule as a whole are in slack

  • They are taut in extension

(Rotation in the transverse plane is only available when the knee is in flexion)

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11
Q

What is Plica?

A

Embryonic folds in capsule

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12
Q

What happens with the Medial Plica when the knee flexes and extends?

A

The plica unfolds during flexion and folds during extension

  • The fold can be pinched between tibia and femur
  • May mimic medial meniscus pathology
  • This is often palpable
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13
Q

What is the role of the Menisci?

A

They reduce localized compressive stress
- increases concavity of tibial condyle (Joint stability)
- Weight distribution
- Reduces friction
- Not a Shock absorber; muscles absorb shock
Also gets nutrition through movement through diffusion and osmosis

Provides proprioception via tension on coronary ligs. and muscular attachments (Popliteus attaches lateral meniscus ; Semimembranosus attaches medial meniscus)

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14
Q

Which meniscus is damage more frequently? What is the MOI? what is the classic presentation?

A

The medial meniscus is damaged more frequently

  • The MOI is usually un-controlled movement of femur on tibia in a closed kinematic chain, this causes pinching and tearing. Classic presentation is “Locking” of the knee.
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15
Q

What happens if a meniscus injury is not repaired?

A

“Its the beginning of the end of your knee”
- There will be an increased of localized pressure (Compressive stress)

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16
Q

How much Osteokinematic movement at the Tibiofemoral Joint with Flexion?

A

0 - 140°

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17
Q

How much Osteokinematic movement at the Tibiofemoral Joint with Hyperextension?

A

WNL: 5 - 10°

> 10 is Genu Recurvatum

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18
Q

How much Osteokinematic movement at the Tibiofemoral Joint with Internal and External Rotation?

A

At full knee extension, there is no rotation that occurs

  • At ~90° of knee flexion (Most rotation of tibia)
    –40 - 45° total axial rotation

(External Rotation has more rotation than Internal Rotation; it s 2:1 Ratio)

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19
Q

How much Osteokinematic movement at the Tibiofemoral Joint with Abduction and Adduction?

A
  • Total movement is ~6°
  • Passive only
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20
Q

What is the Arthrokinematics movement at the Tibiofemoral joint during Open Chain Knee Extension?

A

The Tibia is moving on the Femur; Concave on Convex

  • During Knee Extension, the Tibia rolls and Glides Anteriorly
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21
Q

What is the Arthrokinematics movement at the Tibiofemoral joint during Open Chain Knee Flexion?

A

The Tibia is moving on the Femur;Concave on Convex

  • During Knee Flexion, the Tibia rolls and Glides Posteriorly
22
Q

What is the Arthrokinematics movement at the Tibiofemoral joint during Closed Chain Knee Extension?

A

The Femur is moving on the Tibia; Convex on Concave

  • During Knee Extension, the Femur Rolls anteriorly and glides posteriorly
23
Q

What is the Arthrokinematics movement at the Tibiofemoral joint during Closed Chain Knee Flexion?

A

The Femur is moving on the Tibia; Convex on Concave

  • During Knee Flexion, the Femur rolls posteriorly and glides anteriorly
24
Q

What does the ACL limit? When is it elongated?

A
  • Anterior Glide of Tibia
  • Posterior Glide of Femur
    (The ACL is elongated during Extension)
25
Q

What does the PCL limit? When is it elongated?

A
  • Posterior Glide of Tibia
  • Anterior Glide of Femur
    (The PCL is elongated during Flexion)
26
Q

What motion elongates both the ACL and PCL?

A

Rotation in the transverse plane

27
Q

With the Screw Home Mechanism, what is required for Maximal Congruence?

A

Lateral Rotation is required for maximal congruence

28
Q

With the Screw Home Mechanism, where does the Line of Gravity (LOG) fall?

A

The LOG falls anterior to a fully extended knee in normal posture

29
Q

Why is the Screw Home Mechanism important?

A
  • It allows for maintenance of the knee extension without muscular effort in normal standing effort.
  • It minimizes need for quad contraction at heel-off during normal gait
30
Q

What motion does the MCL restrict? When is the MCL Taut?

A
  • Valgus
  • Extension
  • Axial Rotation (Especially knee ER)
  • MCL is taut in Full Extension
31
Q

What motion does the LCL restrict? When is the LCL taut?

A
  • Varus
  • Extension
  • Axial Rotation
  • LCL is taut in Full Extension
32
Q

How can the interaction with the quads affect the ACL?

A

Contraction of the quads extends the knee and slides the tibia anterior relative to the femur.

33
Q

How can the interaction with the hamstrings affect the ACL?

A

Hamstring activation can limit anterior glide and tension on the ACL. (Because the hamstings place a posterior force on the tibia.
- If the hamstrings are activated during the Anterior Drawer Test, it can result in a False-Negative

34
Q

What is a common MOI for the MCL?

A
  • Valgus producing force with foot planted
  • Severe hyperextension
35
Q

What is a common MOI for LCL?

A
  • Varus producing force with foot planted
  • Severe hyperextension
36
Q

What is a common MOI for the Posterior Capsule?

A
  • Hyperextension or combined hyperextension with external rotation
37
Q

What is a common MOI of the ACL?

A
  • Large valgus producing force with the foot firmly planted
  • Large axial rotation torque applied to knee with the foot firmly planted
  • Severe hyperextension
38
Q

What is a common MOI of the PCL?

A
  • Falling on a fully flexed knee (w/ ankle fully plantarflexed)
  • Any event that causes a forceful posterior translation of the tibia or anterior translation of the femur, especially while the knee is flexed
  • Large axial rotation or valgus-varus applied torque to the knee with the foot firmly planted, especially while the knee is flexed.
  • Severe hyperextension of the knee causing a large gapping of the posterior side of the joint
39
Q

What is the Arthrokinematics with the Patellar-Femoral joint during extension?

A

There is a proximal glide during extension

Also as the knee angle changes, the contact areas change

40
Q

What are Major Pathologies linked to abnormal tracking?

A
  • Chondromalcia (Abnormal growth of cartilage)
  • DJD

Most Common: Excessive Lateral Knee Tracking secondary to Large Q-Angle

41
Q

T/F: As the knee flexion increases, compressive forces increases?

A

True

42
Q

What are the two interrelated factors associated with joint compressive force on the Patelleofemoral Joint?

A
  • Force within the quad muscle
  • Knee flexion angle
43
Q

What functional causes lead to excessive lateral tracking of the patella?

A
  • Adhering of the IT band on Vastus Lateralis
  • Tightness of quads
  • Weakness of the hip abductors and external rotators
44
Q

What structural causes lead to excessive lateral tracking of the patella?

A
  • Genu Valgus
  • Femoral Anteversion
  • External Tibial Torsion
45
Q

With abnormal forces on the Patellofemoral joint (“Excessive lateral tracking”), what is associated with chondromalcia?

A
  • Excessive compressive force on lateral P-F
  • Insufficient compressive foce on medial P-F
    –Cartilage develops abnormally due to poor nutrition
46
Q

Why is the Pes Anserinus group important?

A

Sartorius, Gracilis, Semitendinosis
- All limit valgus and ER
- At least on is activated when weight-bearing because of their actions at the hip joint

47
Q

What are the forces on the Tibiofemoral joint with Genu Valgum?

A
  • The medial structures are under tension
  • The lateral structures get shortened and tight over time
  • There is an increase of compression on the lateral condyle
  • Medial knee pain due to injuries to lig. and capsule
  • Lateral knee pain due to injury to meniscus and articular damage

Will get DJD sooner on medial side
Most like to injure LCL

48
Q

What are the forces on the Tibiofemoral joint with Genu Varum?

A
  • Lateral structures are under tension
  • The Medial structures get shortened and tight over time
  • There is an increase of compression on the medial condyle
  • Lateral knee pain due to injuries of lig. and capsule
  • Medial knee pain due to injury to meniscus and articular damage

Will get DJD sooner on lateral side
Most likely to injure MLC

49
Q

What is a way to minimize risk of ACL tear?

A

With motor control training

Ex. How to land from a jump

50
Q

How happens if a person has weakness in the knee extensors?

A
  • If the knee begins to flex or buckle, the muscles cannot stop it, so we choose to stay in extension
  • Over time, can develop Genu Recurvatum (Hyperextended Knee)

USA Term 2 (46 decks)

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