Knee Joint Flashcards
1
Q
How many degrees of freedom does the knee joint have
A
- 2 DOF
- flexion/extension
- internal/external rotation
2
Q
Where does the ACL run
A
- runs from anterior tibia to posterior femur
3
Q
Describe the femur
A
- medial condyle projects further to account for femur angulation
4
Q
Describe the tibia
A
- medial condyle is 50% larger than the lateral condyle and is slightly concave
5
Q
Describe the patellar groove
A
- groove is higher on the lateral side to help restrain the patella
6
Q
Purpose of the intercondylar notch
A
- provides passage for the ACL and PCL
7
Q
Define genu valgum
A
- less than 170 degrees
8
Q
Define genu varum
A
- 180 degrees or higher
9
Q
Normal genu angle
A
- 170 to 175 degrees
10
Q
What reinforces the anterior capsule
A
- patellar reticular fibers
- quadriceps femoris
- patellar tendon
11
Q
What reinforces the lateral capsule
A
- LCL
- lateral patellar reticular fibers
- IT band
- biceps femoris
- tendon head of gastrocnemius
12
Q
What reinforces the posterior capsule
A
- oblique popliteal ligament
- arcuate popliteal ligament
- popliteus
- gastrocnemius
- hamstrings
13
Q
What limits knee hyperextension ROM
A
- posterior capsule reinforcements
14
Q
What reinforces the medial capsule
A
- MCL
- medial patellar retinacular fibers
- expansions from semimembranosus
- sartorius
- gracilis
- semitendinosus
15
Q
Describe bursae
A
- up to 14 in the knee
- protect important tissue from friction
16
Q
What enhances tibiofemoral articular congruence
A
- menisci
- capsule
- ligaments
- muscles
- bodyweight
17
Q
What do the menisci look like
A
- medial menisci is C-shaped
- lateral menisci is O-shaped
18
Q
Describe the menisci
A
- function as shock absorbers, increase contact area, & weight distributors
- only the outer 1/3 is vascularized which is dense with Ruffini/Pacinian corpuscles & GTOs
19
Q
Normal flexion & extension ROM
A
Flexion: about 130 to 140 degrees
Extension: about 5 to 10 degrees past straight
20
Q
What direction is roll and slide during tibial on femoral extension
A
- same direction
21
Q
What direction is roll and slide in during femoral to tibial extension
A
- opposite directions
22
Q
Describe the screw home mechanism
A
- tibia rotates laterally/externally as it moves into extension
- femur rotates medially/internally as it moves into extension
- occurs in terminal 30 degrees of extension
- popliteus “unlocks” the screw home position
23
Q
Normal internal & external rotation ROM
A
- at 90 degrees knee flexion you have 40 to 45 degrees of total transverse ROM
- at 0 degrees knee flexion you have no transverse ROM
24
Q
What is the close packed position for the knee
A
- full knee extension
25
Describe the MCL
- primarily resists valgus
- also resists external rotation and some internal rotation
- moving distally it runs posterior to anterior
26
Describe the LCL
- thick, cord like, vertically oriented
- blends with biceps femoris
- primarily resists varus
- also resists axial rotation, probably more external rotation
- does not attach to lateral meniscus
27
When is the ACL taut
- increasingly taut in extension
- resists anterior tibial translation & tibial internal rotation
- obliquely oriented
28
When is the PCL taut
- increasingly taut in flexion
- resists posterior tibial translation on a fixed femur
29
ACL mechanism of injury
- landing and cutting mechanics are thought to predispose ACL to injury
- typically associated with valgus collapse
30
Normal translation for anterior tibial on femur
- 10 mm
31
What decreases the tension on the ACL during knee flexion
- when the hamstrings fire with the quads
32
Where is the maximal contact between the patella and femur
- maximal contact at 90 to 60 degrees knee flexion
33
What causes the bowstring effect at the patella
- the quads line of pull is slightly lateral
34
Describe the Q-angle
- the intersection of ASIS to center of patella to tibial tuberosity
- represents line of pull of quads
- normal for females is 18 to 22 degrees
- normal for males is 15 to 18 degrees
35
How much is knee extension is rectus femoris responsible for
- about 20 % and is also a powerful hip flexor
36
At what degree does the external torque on the knee joint hit the red zone for both femoral to tibia and tibia on femoral
- 45 degrees of knee flexion
37
Maximum extension torque production coincides with both
- maximum internal moment arm
- mid range muscle length
- maximal leverage for internal extensor torque production occurs between 60 to 20 degrees knee extension
38
When is max flexion torque on the hamstrings
- maximized near full knee extension between 50 to 90 degrees knee extension
- combined internal & external rotation torque potential maximized near 90 degrees knee flexion
39
Maximum torque production based on quadriceps : hamstring ratio
- 3:2 ratio mostly coming from quads
40
Normal weight bearing in gait
- line of force passes slightly medial to joint center with slightly higher weight bearing on medial condyle
- valgus -> increased force on lateral condyle
- varus -> increased force on medial condyle
41
Medial meniscus connective tissue attachments
- coronary ligaments, transverse ligament
- MCL, ACL
- quadriceps, semimembranosus
42
Lateral meniscus connective tissue attachments
- coronary ligaments
- ACL, PCL
- wuadriceps, semimembranosus, popliteus
43
What can cause windswept defomity
- a poorly fitted wheelchair
44
What can cause windswept deformity
- a poorly fitted wheelchair
45
Describe squinting patella
- patella points medially & is tilted I the frontal plane
