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POTH 225 - Intro to Biomechanics > L4 - Biomechanics of the knee > Flashcards

L4 - Biomechanics of the knee Flashcards

1
Q

Name the components of the knee joint.

A

Knee = tibiofemoral and patellofemoral joints
- Femur
- Tibia
- Patella

Also Superior tibofibular
- Tibia
- Fibular

See NDC p.3 for illustration

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2
Q

Describe the femur.
- orientation
- articular surfaces

A

Femur angled from the vertical to medial

  1. Medial and lateral condyles: articulate with tibia
  2. Patella surface: articulate with patella

See NDC p.4 for illustration

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3
Q

Describe the difference between the medial and lateral condyle of the femur.

A

Medial condyle articulating surface is larger anterior-posterior

Lateral condyle anterior surface extends further anterior
–> Prevent lateral patella dislocation

See NDC p.5 for illustration

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4
Q

Describe the different sizes of tibial articular surface.
What are the 2 functions of this difference? (2)

A

Tibial plateau:
Media tibia plateau is larger than lateral plateau
- Increased loading medial
- Helps decrease stress (force/area)

See NDC p.6 for illustration

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5
Q

Name the stabilizing structures of the knee.

A
  1. Menisci
  2. Collateral ligaments
  3. Cruciate ligaments
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6
Q

Describe the meniscus. (4)
- what
- shape
- between
- blood supply
What is its function?

A
  1. Fibrocartilage discs
  2. Wedged shape
  3. Between femur and tibia
  4. Some blood supply peripheral

Increase contact area between tibia and femur
–> approximately doubles the area = decreases stress
(stress=force/area)

See NDC p.7-8 for illustration

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7
Q

Describe the knee joint.
- classification
- possible motion

A

Modified hinge joint – 2 degrees of freedom (DOF)
- Flexion & extension (sagittal plane)
- Medial & lateral rotation (transverse plane)
(minimal adduction and abduction)

See NDC p.10-11 for illustration

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8
Q

Why do some people claim that the knee has 6 degrees of freedoms?

A

Some disagreement (6 DOF) : Conjunct rotation and translation

Yes, it happens but not controlled by body.

See NDC p.10-11 for illustration

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9
Q

Name the ranges of knee range of motion.

A
  1. Flexion ~140°
  2. Extension ~0°
  3. External (lateral) rotation ~45°
  4. Internal (medial) rotation ~30°
  5. Abduction/adduction few degrees

See NDC p.12 for illustration

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10
Q

What are the angles of knee flexion required for these activities of daily living?
- Walking
- Sit to stand-standard chair
- Sit to stand- low chair
- Stairs
- Out of bath

A

Walking 67°
Sit to stand-standard chair 99°
Sit to stand- low chair 105°
Stairs 99°
Out of bath 138° –> other option: shower bench

See NDC p.13 for illustration

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11
Q

Describe the variation in the sagittal knee angle during gait. (4)

A

Before hitting ground: knee extended

Hit the ground: knee flexes (absorb chock)
–> quads are preventing too much flexes

Single leg stance: extension again to clear other leg

Leg in the air: a lot of flexion to clear the ground

See NDC p.14 for the graph

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12
Q

What are the peak joint reaction force going through the knee during each activity? Sort them smallest to biggest.
- Level walking
- Stair climbing
- Lifting
- Jogging
- Squatting

A
  1. Lifting 2.12 BW
  2. Level walking 3-4 BW
  3. Stair climbing 5.4 BW
  4. Squatting 7.6 BW
  5. Jogging 12.4 BW
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13
Q

REVIEW
What does the convcave-convex rule stipulate?

A

“If the bone with the concave surface moves on the convex surface, the concave articular surface glides
in the same direction as the bone segment’s roll”
–> Example: MP joint

See NDC p.16 for illustration

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14
Q

REVIEW
What does the convex-concave rule stipulate?

A

“If the bone with the convex joint surface moves on the bone with the concave surface, the convex surface glides in the direction opposite the bone rolling motion.”
–> Ex: glenohumeral joint

  • Joint glides = accessory movements

See NDC p.16 for illustration

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15
Q

Does the concave-convex and convex-concave rules work for the knee? How about shoulder?

A

NOOOOOOOOOOOOOOOO
The uneven condyles of the knee joint make it impossible for this rule to apply.

See NDC p.18-20 for illustration

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16
Q

Describe the screw-home mechanism in an open kinetic chain.

A

Leg in air = tibia moves relative to femur

Lateral (external) rotation of tibia on femur during extension

Medial (internal) rotation of tibia on femur during flexion

See NDC p.22 for illustration

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17
Q

Describe the screw-home mechanism in a closed kinetic chain.

A

Leg on ground = femur moves relative to tibia

Medial (internal) rotation of femur on tibia during extension

Lateral (external) rotation of femur on tibia during flexion

See NDC p.22 for illustration

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18
Q

Joint surface motion - SUMMARY
Describe knee flexion in a closed kinetic chain. (4)
- femur
- roll
- condyles

A
  • Femur laterally rotates w.r.t. tibia
  • Posterior roll of femur- contact migrates posterior
  • Lateral femur condyle translates posterior w.r.t. tibia
  • Medial femur condyle moves less than lateral side

*w.r.t = with relation to

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19
Q

Joint surface motion - SUMMARY
Describe knee extension in a closed kinetic chain. (4)

A
  • Femur medially rotates w.r.t tibia
  • Anterior roll of femur- contact migrates anterior
  • Lateral femur condyle translates anterior w.r.t. tibia
  • Medial femur condyle moves less than lateral side

*w.r.t = with relation to

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20
Q

What is the difference between a open kinetic chain and a closed kinetic chain?

A

Open: foot not on the ground
–> tibia is moving

Closed: foot is on the ground
–> femur is moving

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21
Q

How can we measure knee alignment?
Describe the method.

A

Mechanical axis angle = Angle between axis 1 and 2
- Axis1: Centre of femoral head to center of knee
- Axis 2: Centre of ankle to center of knee

See NDC p.26 for illustration

22
Q

What angle represents a normal knee alignment?

A

Normal is ~2° varus

See NDC p.26 for illustration

23
Q

What is varus?
Describe the axes.
What is the common name?

A

Knees point medially.

Distal segment (tibia) deviates medially on proximal segment (femur)
–> ankle-knee axis is outward

Common name: Bow leg

See NDC p.27 for illustration

24
Q

What is vaLgus?
Describe the axes.
What is the common name?

A

Knees (and often toes) point outward

Distal segment (tibia) deviates laterally on the proximal segment (femur)
–> ankle-knee axis going inward

Common name: Knock knee

See NDC p.27 for illustration

25
What happens in knee ostheoarthritis?
Deterioration of joint tissue (bone, cartilage) See NDC p.28 for illustration
26
How does a varus alignment affect the likelyhood of developping knee ostheoarthritis? Why?
Increased risk of medial compartment knee OA development and progression. Ground reaction force passes medial to knee --> larger lever arm = larger moment + torque pulls knee inward (knee adduction) ----> larger load on medial compartment See NDC p.29 for illustration
27
How does a valgus alignment affect the likelyhood of developping knee ostheoarthritis? Why?
Increase risk of lateral compartment knee OA development and progression Ground reaction force passes through the knee --> smaller lever arm = smaller moment , less torque = less knee adduction (pulling knee inward) ----> larger load on lateral compartment See NDC p.29 for illustration
28
What can be done to correct knee alignment? How does this slow knee OA?
High tibial osteotomy - Corrects limb alignment by changing mechanical axis angle Decrease medial/lateral compartment loading --> by reducing varus/vaLgus, change load from medial to lateral or vise-versa ------> Slow knee OA disease progression
29
Research numbers. Is high tibial osteotomy an effective treatment for OA? (4)
1. ↓ mechanical axis angle 2. ↓ in knee adduction moment during gait 3. ↓ pain 4. ↑ function 2 and 5 years after high tibial osteotomy
30
Name the knee collateral ligaments.
1. Medial collateral ligament (MCL) 2. Lateral collateral ligament (LCL)
31
Describe the medial collateral ligament. - function - injured...?
Stabilize against valgus (abductor) force Commonly injured: foot planted, struck on outside of knee See NDC p.35 for illustration
32
Describe the lateral collateral ligament. - function - injured...?
Stabilize against varus (adductor) force Less often injured, usually with multi-ligament injuries See NDC p.35 for illustration
33
Name the cruciate ligaments of the knee.
1. Anterior cruciate ligament (ALC) 2. Posterior cruciate ligament (PCL)
34
What is the function of the anterior cruciate ligament (ALC)?
Resist anterior glide of tibia --> maybe rotation, varus/valgus See NDC p.36 for illustration
35
What are the functions of the posterior cruciate ligament (PLC)?
Resists: 1. Posterior glide of tibia 2. Rotation, 3. Varus (knee adduction) 4. Valgus (knee abduction) See NDC p.36 for illustration
36
How can injury to the ACL occur WITH a contact?
- Foot planted + Femur driven posterior - Sometimes Rotation ex: someone falling onto your knee, forcing it posterior --> tibia glides posterior relative to femur See NDC p.37 for illustration
37
How can injury to the ACL occur WITHOUT a contact?
- Landing, Deceleration, Pivoting/cutting - Knee/hip in extension + valgus - Quadriceps overload Your own muscle/leg position tears your ACL
38
What is the most common way to injure your ACL?
Non-contact way more common than with contact.
39
Describe the mechanism of injury for the ACL. - Back - Hips - Knee - Tibial rotation - Landing pattern
Back: forward flexed, rotated opposite side Hips: adduction, internal rotation Knee: less flexed, vaLgus Tibial rotation: Internal or external Landing pattern: one foot out of control, unbalanced See NDC p.38-39 for illustration
40
Describe the risk of ACL injury in men VS women.
Females have higher rate of non-contact ACL injuries than males (0.14 vs. 0.05/1000 hours) See NDC p.40 for graph
41
Why do women have higher rate of non-contact ACL injuries?
Differences in joint angles during movements --> Females knee more abducted and extended during landing See NDC p.40 for graph
42
Did the Fifa11+ prevention program work to prevent ACL injury?
FIFA 11+ reduced injuries by 39% in soccer players Decreased knee valgus (abduction) moments in female children (n=51) during double leg jump, but not during other activities --> No change in knee angles
43
Why is it harder to stand in squat VS straight? --> closed kinetic chain
When straight, ground reaction force goes through your knee --> the torque is low because it passes through knee When squatted, ground reaction force does not go through your knee --> the torque is high because there is a moment arm for trunk weight Moment arm of the trunk weight increases with increasing knee flexion = More quadriceps work to balance CKC ↑ Knee flexion = ↑ dG (ground reaction force) =↑ MG (ground reaction force) = ↑ MQ (quads) See NDC p.44 for illustration
44
Why is it harder to keep your leg extended off the ground VS hanging down. --> open kinetic chain
Moment arm of ankle weight and leg increases as knee extends increasing flexion moment --> More quadriceps work (extension moment) to balance OKC ↑ Knee flexion = ↓ dG (ground reaction force) = ↓ MG (ground reaction force) = ↓ MQ (quads) --> less work required my quadriceps See NDC p.45 for illustration
45
Describe the patella.
1. Sesamoid bone 2. Imbedded in quadriceps tendon
46
What are the functions of the patella?
1. Increase the moment arm of the quadriceps tendon --> increase moment arm = muscle do not have to force as much 2. Protects quadriceps tendon from excessive friction from the femur See NDC p.47 for illustration
47
What is the Q-angle? What is the normal Q-angle for men and woman?
Q-angle = Angle between line 1 and 2 - Line 1- ASIS to patella center - Line 2- Tibial tubercle to patella center Normal - women: 18° - men: 13°
48
What causes the Q-angle to be larger than normal? What are the consequences?
Represent lateral pull of quadriceps on patella --> Increase Q angle, increase lateral pull SO: Increased risk of anterior knee pain and lateral patella dislocation with increased Q angle
49
What structures prevent patella dislocation? (3)
1. Lateral femoral condyle (larger anterior) 2. Medial extensor retinaculum 3. Vastus medialis muscle
50
Describe the motion of the patella during knee flexion and extension. When is there the most and least contact between the patella and femur?
Patella glides inferior during knee flexion and glides superior during knee extension. ↑ knee flexion = ↑ contact between femur and patella ↓ knee flexion = ↓ contact between femur and patella Full knee extension = minimal contact Full knee flexion = maximal contact See NDC p.50 for illustration
51
Describe the change in the patella joint force (PJF) in knee flexion.
Patella joint force increase with increase knee flexion because the angle of the quadriceps becomes more posterior. OKC and CKC ↑ knee flexion = ↑ posterior Q, ↑ patella JRF See NDC p.51 for the graph
52
Why do patellar JRF forces continue to rise with knee flexion in CKC while it drops with OKC (at about 50°)?
OKC ↑ Knee flexion = ↓ dG (ground reaction force) = ↓ MG (ground reaction force) = ↓ MQ (quads) --> ↓ force of quads = ↓ patella JRF CKC ↑ Knee flexion = ↑ dG (ground reaction force) =↑ MG (ground reaction force) = ↑ MQ (quads) --> ↑ force of quads = ↑ patella JRF See NDC p.52 for the graph

POTH 225 - Intro to Biomechanics (14 decks)

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