anatomy of knee

Question 1

what type of joint is the knee?

Answer 1

bicondylar hinge joint

Question 2

what is the function of the locking mechanism of the knee?

Answer 2

reduces the amount of energy required when the knee is extended

Question 3

how does the shape f the femur assist in the locking and rolling mechanisms of the knee?

Answer 3

locking: the most inferior aspect of the femur is flat, which allows for stabillity when the knee is extended
flexion: during flexion the post possterior part of the femur is involved , this is ronund and allows rolling of the joint

Question 4

what are the 3 things that allow locking of the knee?

Answer 4

1. shape- shape of the femur allows the flat surface of the femur to be in contact with the tibia during extention, and this is more stable
2. rotation- femur medially rotates in relation to the tibia during extention which tightens the ligament of the knee
3. centre of gravity- centre of gravity is right through the patella, which maintains the knee in extention

Question 5

what is the importance of the femoral angle?

Answer 5

• is the angle between the mechanical axis and atomical axis (15degrees)
• adducts the femur so it sits below the pelvis, which is critical for weight bearing

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Question 6

what is a varus deformity?

Answer 6

• decreased q angle
• because of medial displacemnt of ibia
• results in bow-leggedness
• results in joint degeneration

Question 7

what is a valgus deforminty?

Answer 7

• increased q angle
• later displacement of femur in relationto tibia

Question 8

what are the extracapsular ligaments of the knee?

Answer 8

medial collateral

lateral collateral

Question 9

what are the intracapsular ligaments of the knee?

Answer 9

• anterior cruciate
• posterior cruciate

Question 10

what is the fiunction of the lateral fibular collateral ligament?

Answer 10

• round cord
• prevents medial displacement of tibia

Question 11

what are is the function of the medial collateral ligament?

Answer 11

• broad flat band
• reinforces the joint capsule
• prevents lateral displacement of tibia (valgus deforminty)

Question 12

what are the functions of the cruciate ligaments?

Answer 12

anterior cruciate ligaments- prevents anterior displacement of tibia on femur

posterior cruciate ligaments- prevents posterior displacement of tibia on femur

both maintain the femur against the tibia- so one ligament is always tense

Question 13

how do the cruciate ligaments pass?

Answer 13

• posterior cruciate- upwards and forward medially
• anterior cruciate ligament- upwards annd backwards laterally

Question 14

why can you laterally rotate your flexed knee more than you can medially rotate it?

Answer 14

• medial rotation tightens ligaments so rotation is just 10 degrees
• lateral rotation unwinds the ligaments so you can rotate 60 degrees

Question 15

how does ACL become injured?

Answer 15

• caused by sharp twisting of the knee
• weaker than PCL soinjured more easily

Question 16

what is the lachman test used for?

Answer 16

• to check for ACL injury
• Patient in supine position with knee bent 20-300 of flexion
• Move tibia anteriorly and posteriorly while maintaining position of femur
• Laxity during this manoeuvre indicates anterior cruciate ligament injury

Question 17

when is the PCL particularly important?

Answer 17

• its the principal stabiliser of flexeed knee
• so especially important when walking down hill

Question 18

what are the menisci of joint?

Answer 18

cresent shaped plates of fibrocartilage

Question 19

what are the functions of the menisci?

Answer 19

• deepen the articulating surfaces for stability
• act as shock absorbers
• provide smooth viscus film for joint

Question 20

what is the unhappy triad?

Answer 20

rupture of…..

• ACL, MCL and medial meniscus attatched to MCL

occurs during contact sports when there has been…

• twisting of a flexed knee and a blow to the lateral side

Question 21

which muscle prevents lateral tracking of patella?

Answer 21

because of the abduction of the femur and the action of rector femoris there is a tendency for patella to tract laterally when walking

• vastus medialis counteracts this lateral pull

Question 22

what are the functions of the patella?

Answer 22

• protects quadraceps tendon from stress during locomotion
• smooth oval facet of posterior surface for articulation with femur

Question 23

what injuries can you get to the extensor mechanism?

Answer 23

• rupture of quadraceps tendon or patellar ligament
• fracture of patella
• disslocation of patella

Question 24

which muslce is responsible for unlocking the knee?

Answer 24

Popliteus unlocks knee joint

• Laterally rotates femur on tibia when foot is on ground

Question 25

what are bursae?

Answer 25

Synovial fluid filled sac lined by synovial membrane

protect and reduce friction

Question 26

what are the different types of bursitis?

Answer 26

bursitis= inflamtation of the bursae due to repetitive movement and direct pressure

prepatellar bursitis (housemaids knee)- leaning forward on knees brings prepatellar bursae in contact with floor

infrapatellar bursitis (clergymans knee)- sitting back on heels brings infrapatellar bursa in contact with floor

Question 27

what is bakers popliteal cyst?

Answer 27

• Abnormal fluid filled sacs in popliteal fossa
• Due to herniation of synovial membrane/bursa
• Common in patients with chronic inflammatory joint disease (e.g. arthritis
• Presents as swelling in the popliteal fossa, which Can affect joint movement
• treat by aspiration and cortisone injection

Question 28

what is the vascular supply to the knee joint?

Answer 28

femoral and popliteal arteries anastamose arount the knee joint

but there is limited blood supply to the intracapsular stuctures- which explains why they are poor to repair following injury