Lecture 3: The Knee Joint

Question 1

What kind of joint is the knee joint?

Answer 1

Synovial hinge

Question 2

Which three bones are involved in the knee joint?

Answer 2

• distal femur
• proximal tibia
• patella

Question 3

What are the 3 articulations involved in the knee joint?

Answer 3

2 femorotibial
> medial and lateral
1 femoropatellar

Question 4

What movements are possible at the knee joint?

Answer 4

• Flexion
• Extension
• Medial rotation of leg, knee joint flexed 90 degrees
• Lateral rotation of leg, knee joint flexed 90 degrees

Question 5

What is ‘locking’ of the knee joint?

Answer 5

As joint approaches full extension, femur undergoes a few degrees of medial rotation on the tibia.

This is called ‘locking’ the knee

Very stable position therefore thigh muscles can relax

Question 6

How is the knee ‘unlocked’?

Answer 6

The knee is ‘unlocked’ by the popliteus muscle which laterally rotates the femur.

Question 7

What is the tibial plateau?

Answer 7

The surface of the tibia above the medial and lateral tibial condyles. (see knee lecture).

Question 8

Why is the femorotibial joint incongruant?

Answer 8

There is a poor fit between the rounded ends of the femoral condyles and and the tibial plateau.

Question 9

When does the joint have most congruence?

Answer 9

In extension

Question 10

What deepens the tibial plateau?

Answer 10

The menisci

Question 11

What are the menisci?

Answer 11

• 2 c-shaped wedges of fibrocartilage

- Thicker at external margins

Question 12

What are the functions of the menisci?

Answer 12

• Increase joint congruency
• Distribute weight evenly
• Shock absorption
• Assist in locking mechanism

Question 13

What are the attachments of the menisci?

Answer 13

• External edges attach to the fibrous capsule of the joint

- Medial meniscus is firmly attached to the tibial collateral ligament

Question 14

What are the causes of menisceal tears?

Answer 14

• Can be due to a sports injury or degenerative changes

Question 15

What ligaments lie within the joint?

Answer 15

• intra-articular

- the anterior & posterior cruciate ligaments (inside the joint capsule)

Question 16

What ligaments lie outside the joint?

Answer 16

• extra-articular

- the fibular & tibial collateral ligaments

Question 17

What is the basic structure of the cruciate ligaments?

Answer 17

Cross each other obliquely in the centre of the knee

Question 18

What is the structure of the posterior cruciate ligament?

Answer 18

The posterior cruciate ligament attaches to the posterior intercondylar region of the tibia and travels supero-anteriorly to insert onto the medial femoral condyle.

Question 19

What is the structure of the anterior cruciate ligament?

Answer 19

The anterior cruciate ligament attaches to the anterior intercondylar region of the tibia and travels supero-posteriorly to attach to the lateral femoral condyle.

Question 20

Which of the cruciate ligaments is the strongest?

Answer 20

PCL is stronger than the ACL

Question 21

What is the function of the PCL?

Answer 21

Prevents posterior displacement of the tibia on the femur
Prevents hyperflexion
Main stabiliser of the flexed knee when weight bearing e.g. walking down hill

Question 22

How might PCL injury occur?

Answer 22

Can be damaged when landing on the tibial tuberosity with the knee flexed.

Question 23

What is the function of the ACL?

Answer 23

Prevents anterior displacement of the tibia on the femur

Prevents hyperextension

Question 24

How might ACL injury occur?

Answer 24

Occurs when knee is hyperextended or force is applied anteriorly.

Question 25

Where is the tibial (medial) collateral ligament?

Answer 25

Flat band attached to medial meniscus

Question 26

What is the function of the medial ligament?

Answer 26

Prevents abduction of the leg at the knee.

Question 27

Where is the fibular (lateral) collateral ligament?

Answer 27

Cord-like band NOT attached to lateral meniscus.

Question 28

What is the function of the fibular collateral ligament?

Answer 28

Prevents adduction of the leg at the knee.

Question 29

What is the function of both collateral ligaments together?

Answer 29

Prevent rotation during extension of the knee contributing to stability while standing.

Question 30

What is the ‘unhappy triad’?

Answer 30

• Caused by excessive lateral twisting of the flexed knee or blow to lateral side of extended knee
• Tears the tibial collateral ligament which is attached the medial meniscus, which also then tears
• ACL may then also tear – as it is taut during flexion
  Common when flexed knees are twisted

Question 31

Which muscles are the main stabilisers of the knee?

Answer 31

• Quadriceps
• Hamstrings (posterior thigh)
• Sartorius
• Gracilis
• Iliotibial tract

Question 32

What is the Q angle?

Answer 32

The angle between the femur on the tibia.

i.e. the femur sits obliquely on the knee joint.

Question 33

Why do women have a larger Q angle?

Answer 33

They have a wider pelvis - femur is more oblique than in males.

Question 34

What is a larger Q angle associated with?

Answer 34

Stronger quad contraction and possible dislocation.

Question 35

What is genu varum?

Answer 35

Bow leg - tibia adducted with respect to femur (i.e. knees bow outwards)

Question 36

What genu valgum?

Answer 36

Knock knee - tibia abducted with respect to femur (i.e. knees knock together)