Week 5: Osteology of the Knee Joint

Question 1

What small triangular muscle attaches to the tibia, proximal to the soleal line?

Answer 1

Popliteus

Question 2

What is the patella?

Answer 2

• Largest sesamoid bone (bones embedded in tendons) - quadriceps tendon
• Increases the moment arm of the quadriceps tendon
• Protects quadriceps tendon from excessive friction (flexion)

Question 3

Is the apex directed superiorly or inferiorly when the patella is in situ?

Answer 3

Inferiorly

Question 4

What structure attaches to the base and sides of the patella?

Answer 4

Quadriceps tendon

Question 5

What structure attaches to the apex of the patella?

Answer 5

Patellar ligament

Question 6

Why is the anterior surface of the patella rough?

Answer 6

Due to the attachment of the quadriceps tendon

Question 7

Why is most of the posterior surface of the patella covered by articular cartilage?

Answer 7

For articulation with the patellar surface of the femur

Question 8

How can you determine whether your specimen is a right or left patella?

Answer 8

Apex will point inferiorly, the lateral facet is broader and deeper than the medial facet

Question 9

What is the role of the vertical ridge of the patella?

Answer 9

Aids in stability of the patellofemoral joint and control of the position of the patella during knee joint motion

Question 10

Describe the influence of the bony morphology for extension of the patella:

Answer 10

Patella sits superiorly on the patellar surface, sideways motion not particularly restricted by the lips of the intercondylar groove

Question 11

Describe the influence of the bony morphology for flexion of the patella:

Answer 11

Patella sits inferiorly on the patella surface
- Little lateral motion as the patella sits down in the intercondylar groove

Question 12

Which position are you most likely to displace/dislocate your patella?

Answer 12

Knee joint in extension, as least stable position

Question 13

What structure resists superior translation of the patella?

Answer 13

Patellar ligament

Question 14

What are the patellar retinacula formed from?

Answer 14

Tendinous expansions of vastus medialis and vastus lateralis, providing further attachment sites into the tibial condyles

Question 15

What is the function of the patellar retinacula?

Answer 15

Maintaining patella stability by resisting displacement of the patella - particularly lateral displacement

Question 16

Does the fibula partake in the knee joint complex?

Answer 16

No, it is external to the knee joint capsule

Question 17

Describe the geometry of the articular surfaces that are in contact when the femur and tibia are placed in extension:

Answer 17

Slightly flattened femoral condyles on flattish tibial plateau

Question 18

Describe the geometry of the articular surfaces that are in contact when the femur and tibia are placed in flexion:

Answer 18

Rounded femoral condyles on the flattish tibial articular surfaces

Question 19

What are the implications of the geometry for stability at the knee joint?

Answer 19

Tibiofemoral joint is most stable in extension - flat on flat condylar morphology is more stable than in flexion where the rounded femoral condyles sit on the flattish tibial surfaces

Question 20

What implications does the morphology of the tibiofemoral joint have on injury?

Answer 20

• More likely to injure knee with some component of joint flexion
• A flexed joint would require more muscle control to maintain stability

Question 21

Describe the morphology of the condyles of the distal femur in the transverse plane:

Answer 21

• Medial femoral condyle is curved in the transverse plane
• Lateral femoral condyle projects posteriorly
• Lateral femoral condyle also extends further anteriorly to form buttress against lateral displacement of patella