Lower Limb: Knee Joint

Question 1

What are the joints within the KJ?

Answer 1

patellofemoral (patella & femur anteriorly)

tibiofemoral (distal femur/condyles & proximal tibia/plateus)

Question 2

When is the knee joint most stable?

Answer 2

Extension

Question 3

Which condyles (medial or lateral) of the tibia & femur are larger & longer?

Answer 3

Medial

Question 4

Which is the fixed, weight bearing joint of the tibiofemoral joint?

Answer 4

tibia

Question 5

What is significant about the inter-condylar region of the tibia?

Answer 5

Non-articular part

attachment of the menisci & cruciate ligaments (tubercle of the intercondylar eminence)

Question 6

Describe the mechanism of the locking & unlocking of the knee joint in extension & flexion

Answer 6

During extension the femur rotates medially on the tibia (due to longer medial articular region) and the tightening of the ACL joint in the last part of extension (15 - 20 degrees)

Unlocking occurs in the early part of flexion due to the active contraction of popliteus which attaches to the lateral condyle, allowing lateral rotation of the femur on the tibia

Question 7

When is the ACL particularly susceptible to damage? what are the consequences?

Answer 7

Last 15-20 degrees of extension when a lateral force is applied (b/c it is tightening with medial rotation of the femur to lock the knee joint)
Usually complete or partial tear resulting in significant haemarthrosis and repair by surgery & graft

Question 8

what is enclosed within the KJ capsule?

Answer 8

attached around articular margins & contains the cruciate ligaments + menisci
Lined internally by synovial membrane

Question 9

What reinforces the KJ capsule?

Answer 9

reinforced by powerful muscles at all aspects
anteriorly - patella tendon, retinacular fibres, quads mechanism
laterally - popliteus, biceps femoris, iliotibial tract
Medially - pes anserinus tendons (tendons that blend into tibia)
posteriorly - oblique popliteal ligament

Question 10

What muscle tendons make up the pea anserinus

Answer 10

Sartorius
gracilis
*bursa
semitendinosous

‘say grace before tea’

Question 11

Where and why are there deficiencies in the capsule of the KJ?

Answer 11

deficiencies allow communication of bursae with the joint
Above the patella - suprapatella bursa
Posteriorly - popliteus tendon + semimembranosus bursa

Question 12

What gives rise to a baker’s cyst?

Answer 12

Thickening of the lining of the bursa at the back of the knee (semimembranosus bursa)

Question 13

What can occur to the bursa in joint effusion & what are the possible consequences of infection in the bursa?

Answer 13

In joint effusion the suprapatella bursa that communicates posteriorly with the joint can inflate

infected material from the bursa can be introduced into the joint space

Question 14

What are the non-communicating bursa of the knee?

Answer 14

3 in relation to the patella & patella ligament
prepatella (anterior to patella)
superficial infrapatella (anterior to ligament + inferior to patella)
deep infrapatella (deep to ligament + inferior to patella)

Question 15

Where are the cruciate ligaments located?

Answer 15

Intracapsular but extra-synovial

intercondylar region of the knee

Question 16

Attachments & function of the ACL?

Answer 16

Anterior tibia to lateral condyle of femur

Prevents anterior displacement of tibia in relation to femur & posterior displacement of femur in relation to tibia

Question 17

Attachments & function of the PCL?

Answer 17

Posterior tibia to medial condyle of femur

Prevents femur slipping forward and tibia slipping backwards in knee flexion

Question 18

When is the PCL susceptible to injury & what are the consequences?

Answer 18

Fall on a flexed knee or ‘bumper bar’ injury

Instability of joint when walking downstairs - have to extend injured knee

Question 19

Describe the medial collateral ligament & its function

Answer 19

flat & broad, adherent to joint capsule & medial meniscus
resists lateral displacement of the tibia
reinforces role of ACL as fibres angled slightly anterior to posterior

Question 20

Describe the lateral collateral ligament & its function

Answer 20

small narrow & not adherent to the capsule
attaches to head of fibula
resists medial movement of tibia & adduction forces
less commonly injured than MCL

Question 21

Other names for the MCL & LCL?

Answer 21

MCL - tibial CL

LCL - fibular CL

Question 22

What is the ‘unhappy triad’?

Answer 22

Injury to ACL, MCL & medial menisci

Question 23

what are the functions of the menisci?

Answer 23

shock absorb
distribute weight
increase area for contact (articulation) due to wedge shape

Question 24

what are the differences between the medial & lateral menisci & what does this mean for their injury?

Answer 24

Medial is adherent to the joint capsule & MCL, lateral is not attached therefore more mobile
medial is avascular and lateral is vascular
Both can be injured by forces to the sides of the joint
Medial more commonly injured due to attachment to MCL (less mobile)
Lateral can be repaired due to vascular nature

Question 25

With what joint movements do the menisci move?

Answer 25

Move with femur in rotation and with the tibia in flexion/extension

Question 26

What connects the menisci?

Answer 26

They are interconnected by the transverse ligament of the knee

Question 27

What maintains the stability of the patellofemoral joint/the alignment of the patella?

Answer 27

1. Muscular mechanism = strong vastus medialis muscle fibres run obliquely & stop the patella laterally displacing
2. medial patella retinaculum
3. raised lip on lateral femoral condyle

Question 28

What creates the groove for the patella to track & what influences its tracking?

Answer 28

The raised lip on the lateral condyle creates a groove for the patella to slide up and down
This is influenced by the angulation of the femur (more lateral at the hip and more medial at the knee)

Question 29

What is a pathology associated with tracking of the patella?

Answer 29

Weak vastus medialis
Tightening of the retinaculum OR
Absence of the lip of the lateral condyle

Abnormal tracking can wear down the cartilage, causing it to soften = Condromalacia patella

Question 30

What factor increases risk of lateral displacement of patella, and thus tracking issues, in females?

Answer 30

Increased width of pelvis as it influences the anglation of the femur

Question 31

What does tracking issues of the patella predispose too?

Answer 31

Sublaxation/dislocation