Knee Joint Flashcards

1
Q

Name the 2 joints in the knee?

A

Tibiofemoral & Patellofemoral

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2
Q

What is the femur covered by?

A

Hyaline Cartilage

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3
Q

What is the tibia covered by?

A

Articular Cartilage

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4
Q

The paatellofemoral joint is enclosed by the same capsule as the one that encloses the _______ .

A

“Knee joint proper”; femoraltibial joint

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5
Q

Communication can be seen between the knee joint space and the ______ .

A

Bursa (above it)

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6
Q

Do articular surfaces provide little or a lot of support?

A

Little (due to the shape)

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7
Q

Name the supporting structures of the knee joint

A

Cruciate ligament (ant & post), Collateral ligament (med & lat), Menisci (med & lat)

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8
Q

Describe the structure of the femur.

A

Distal end: has a surface with which the patella will articulate. The surface is reciprocally shaped (triangular)
Femur terminates as the condyles.

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9
Q

Describe the femoral condyles

A

They differ in shape.
Medial femoral condyle is longer than the lateral (Lateral is also wider).
The length is about 1cm different.

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10
Q

Why is it important that the condyles differ in size?

A

It’s important for when the joint is going from the flex -> ext position

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11
Q

What is between the condyles?

A

Intercondylar area (the notch is closer to the lateral side). It contains the ACL.

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12
Q

What can happen to the intercondylar area narrows?

A

The surrounding ligaments become irritated and frayed as it passes in the notch

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13
Q

Describe the tibial plateau

A

Medial surface is larger and longer, and the lateral surface is also shorter to correspond with lateral condyle of femur.

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14
Q

Are the structures in the tibial plateau articular or not?

A

They are non-articular. The region has an elevation in the centre. It is a site of attachment of two of the pairs of supporting structures.
It’s also the site of attachment of menisci and cruciate ligamnets

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15
Q

Describe when the knee extends

A

Femur rotates medially on fixed tibia, passive “screw-home” mechanism. This occurs in the last 15-20 degrees of extension.

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16
Q

Describe the ligaments during knee extension.

A

All ligaments are tight when the knee is extended. The Screw-home mechanism occurs about the ACL. Thus, ACL is most prone to injury if anything goes wrong while the knee extends.

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17
Q

Describe what happens when the knee flexes.

A

This is an active contraction of the Popliteus muscle.

Femur rotates laterally on flexed tibia. The rotation can only occur after the joint is unlocked.

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18
Q

Describe how the popliteus runs through the knee joint

A

It runs through the capsule, attaches to the tibia and passes up to attach to the lateral surface of condyle.

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19
Q

Describe the coloured areas

A

Purple: synovial membrane
Dark green: PCL (larger), ACL
Light green: capsule (incorporate the patellofemoral joint)
Blue: Menisci

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20
Q

Describe the movement of cruciate ligaments during development

A

They commence on the posterior aspect of the joint and migrate in. As they move forwards, they push the synovial membrane in front of them (but don’t become completely enclosed). Hence, they end up between ligament and membrane. Since synovial membrane is highly vascular; ACL tear -> bleeding.

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21
Q

Are the synovial membrane vascular?

A

Yes. Very.

22
Q

Does the capsule have lots of openings? What does this make the capsule prone to?

A

Yes. Infections.

23
Q

What bursas are in the knee joint capsule?

A

Suprapatellar, popliteus , semimembranous

24
Q

What happens when the bursa becomes inflamed?

A

They become thickened -> Baker’s Cyst. Irritated in knee joint flexion + painful.

25
Q

Describe Pes Anserinus.

A

Goose’s Foot. It is the conjoined tendons of three muscles that insert onto the anteromedial (front and inside) surface of the proximal extremity of the tibia. The muscles are the sartorius, gracilis and semitendinosus.

Note: CNVII also has this

26
Q

Name every bursa in/around the knee joint:

A
Posterior: Popliteus/semimembranous.
Suprapatellar
Prepatellar
Superficial infrapatellar
Deep infrapatellar (all non-communicating but dusceptible to irritation)
27
Q

Describe attachment/insertion of PCL

A

Posterior tibia to medial condyle of femur

28
Q

Cruciate ligaments are primary stabilisers in which direction?

A

A-P

29
Q

Describe PCL function when walking down the stairs

A

During knee flexion, the PCL stops femur from sliding off the tibial plateau [limits posterior displacement of tibia]. Patients with a PCL tear will walk down stairs with their knee in an extended position.

30
Q

Describe ACL in knee flexion/extension.

A

Flexion: ACL is twisted on itself. Extension: it untwists and pulls lateral condyle in medial direction (passively)

31
Q

ACL acts as a counter to which muscles/

A

Hamstrings (hamstrings pull tibia posteriorly)

32
Q

How do you fix an ACL tear?

A

Grafft (taken from midportion of patella tendon), insert into a hole drilled from tibia into medial aspect of outer lateral condyle of femur.

33
Q

How can you damage the PCL?

A

Fall on flexed knee, bumper bar impact

34
Q

What is the Lachman’s test?

A

Stabilise knee, then a gentle anterior translation force is applied to the proximal tibia. Note: Application of an anterior tibial translation force with significant anterior translation of the tibia on the femur in an ACL-deficient knee.

35
Q

Describe the parts of MCL

A

Superficial part, Deep part.

36
Q

Describe function of MCL.

A

Resists lateral displacement of tibia. They also limit anterior displacement of tibia with the femur (reinforcing role of ACL).

37
Q

Can the MCL take over ACL function when ACL is damaged?

A

Yes. They have similar functions.

38
Q

Describe the attachment/insertion of LCL

A

From epicondyle -> Head of fibula.

39
Q

How is the LCL separated from the lateral meniscus?

A

By the popliteus tendon.

40
Q

What is the function of LCL?

A

Resists varus (adduction) forces.

41
Q

Function of Menisci?

A

Shock absorb + Weight distribution. It moves with femur in rotation, and tibia with flexion/extension.

42
Q

What is the shape of the menisci and what function does this have?

A

Menisci are wedge-shaped, which increases area of contact by 1/3

43
Q

Which meniscus is more likely to be injured out of the two?

A

Medial, due to it being stuck in position by attachment to MCL.

44
Q

Describe how the menisci lie in the joint cavity.

A

Moon-shaped, medial + lateral side of the joint. Synovial fluid covers them but they are not covered by synovial membrane.

45
Q

How can meniscal tear/injury result in a locked knee?

A

Additional cartilagenous structure gets in the way of articular surfaces.

46
Q

Describe blood supply to meniscus.

A

Lateral: “red zone”, blood supply (which makes repair possible). Medial: “white zone”, no blood supply

47
Q

Describe position of femur from hip to knee joint.

A

Lateral position at hip to more central position at knee joint. Orientation is slightly exaggerated in females due to pelvis.

48
Q

What are the 3 structures which help maintain normal alignment of the patellofemoral joint?

A
  1. Strong vastus medialis muscle (active_
  2. Medial patellar retinaculum.
  3. Raised lip of lateral femoral condyle (passive)
49
Q

What happens if the lip of patellofemoral joint is missing/reduced in size?

A

Patella prediscposed to subluxation or dislocation

50
Q

What happens if the patellofemoral joint tracts abnormally?

A

Articular surface may wear away and soften. This leads to ‘Chondromalacia patella’.

51
Q

How can the susceptibility of joint dislocation/subluxation/etc be measured?

A

Q angle: Angle between the tendon of quads and patella tendon