Kinesiology of the knee complex

Question 1

what maintains the dynamic stability of the knee?

Answer 1

the flexors and extensors

Question 2

what maintains the static stability of the knee?

Answer 2

the ligaments. (cruciate and collateral)

Question 3

main functions of the knee

Answer 3

weight bearing and locomotion

Question 4

bones that make up the knee joint?

Answer 4

femur
tibia
fibula
patella

Question 5

What is the “true” knee joint?

Answer 5

tibiofemoral (btwn tibia and femur)

Question 6

tibiofemoral joint is the articulation of what?

Answer 6

convex femoral condyles and the concave tibial plateaus.

Question 7

Femoral articular surfaces (knee)

Answer 7

-Large med/lat condyles.
Medial is .667 inches longer than the lateral due to an angled femur.

-patellar groove

Question 8

tibial articular surfaces (knee)

Answer 8

-med/lat plateaus
medial is about 50% larger than lateral
(lateral cartilage tends to be thicker)

Question 9

Valgus (genu valgum)

Answer 9

knock knee.
increases compression on lateral side
increases tension on medial side
<=165 degrees (femur and tibia?)

Question 10

Varus (genu varum)

Answer 10

bow-leg.
increases compression on medial side
increases tension on lateral side.
>=180 degrees (femur and tibai?)

Question 11

tibiofemoral joint
(type, DOF)

Answer 11

hinge joint
-double condyloid joints side-by-side (so no lateral rocking like just one would have)
DOF = 2 (sagittal as well as some transverse)

Question 12

ROM of the knee

• flex/ext
• IR/ER

Answer 12

flexion 140 degrees. extension 10 degrees from 0

When flexed at least 90::

• IR = 40-45
• ER 2x > IR

Question 13

What is the screw-home mechanism?

Answer 13

important for locking knee. During the last 30 degrees of extension, rotation occurs in the joint so max congruency is achieved. Medial condyle of femur is bigger.

open chain: tibia will externally rotate
closed chain: femur will internally rotate

Question 14

3 factors guiding the “screw-home” mechanism

Answer 14

1) shape of the medial femoral condyle
2) tension in ACL
3) lateral pull of quadriceps

Question 15

Tibiofemoral menisci

-functions

Answer 15

• aid in weight distribution, shock distribution, and reduce friction.
• supports knee, enhances stability and cushioning when weight bearing.
• • thick peripheral borders and taper to a thin inner edge to deepen facets and increase stability.

Question 16

Medial meniscus of knee

Answer 16

“C” shaped

Question 17

Lateral meniscus of knee

Answer 17

pretty much full circle

Question 18

Medial (tibial) collateral ligament

MCL

Answer 18

broad and long ligament. secures tibia to femur. resist a valgus (stretching of medial side) position.

**main function = prevents ABd of tibia

Question 19

Lateral (fibular) collateral ligament

LCL

Answer 19

cord-like. secures fibula to femur.
resists a varus position prevents ADd of lower leg.

helps control motion of extension as well as medial rotation.

Question 20

Cruciate ligaments

anterior and posterior

Answer 20

• very strong and cord-like.
• they cross each other and are named according to attachments at tibia

***help limit extension and prevent rotation in extension

Question 21

ACL mechanics
(going from extension to flexion)

Answer 21

in flexion the ACL is pretty slack. as you progress through extension it becomes more taught.

*most injuries occur during extension

Question 22

ACL testing and influence of hamstrings and quads

Answer 22

ACL resists anterior slide of tibia

• quads try to slide tibia anteriorly
• hamstrings resist this (therefore aid in func. of ACL)

** hamstrings could give a false result to anterior drawer test.