Knee Flashcards
What is the angle of the knee on its lateral side?
170°-175°
The normal alignment of the knee is referred to as genu ____
valgum
If the frontal plane angle of the knee is less than 170° it is called excessive genu ____, or “knock-knee”.
valgum
If the frontal plane angle of the knee is greater than 180° it is called genu ____, or “bow-leg”.
varum
2 joints of the knee
tibiofemoral joint and patellofemoral joint
Describe the articulation at the tibiofemoral joint
Articulations between large, convex femoral condyles and nearly flat, smaller tibial condyles
What portion of the menisci are attached to the tibia?
The anterior and posterior horns
What attaches the external edges of each meniscus to the tibia?
coronary (or meniscotibial) ligaments
The medial and lateral menisci are attached anteriorly by what ligament?
the slender transverse ligament
What muscles attach to the medial meniscus?
- Quadriceps
- Semimembranosus
What muscles attach to the lateral meniscus?
- Quadriceps
- Semimembranosus
- Popliteus
Where is blood supply to the menisci greatest?
near the peripheral (external) border
Describe the shape of the medial and lateral meniscus
- Medial meniscus has oval shape
- Lateral meniscus has more circular shape
Complete lateral meniscectomy increases peak contact pressures at knee by __%
230%
What is the MOI for a meniscus tear?
forceful axial rotation of femoral condyles over partially flexed and weight-bearing knee
Medial meniscus injured ____ as frequently as lateral meniscus
twice
What is the MOI for a medial meniscus tear?
axial rotation and external valgus force applied to lateral aspect of knee
How many degress of freedom does the tibiofemoral joint have? What are they?
2
- Flexion and extension
- Internal and external rotation
Frontal plane motion at the knee occurs passively and is limited to _° - _°.
6° - 7°
From the tibial-on-femoral perspective which bone is stationary? Which is stationary from the femoral-on-tibial perspective
femur
tibia
The migrating path of the ML axis of rotation for flexion and extension of the knee is called what?
the “evolute”
What are the 2 biomechanical and clinical implications of the migrating ML axis of rotation?
1) alters the length of the internal moment arm of the flexor and extensor muscles of the knee
2) external devices that attach to knee (goniometer) rotate about a fixed axis of rotation which means they may rotate in a dissimilar arc than the leg
From a tibial-on-femoral perspective, external rotation of the knee occurs by ____ rotation of the tibia
external
Motion is the same
From a femoral-on-tibial perspective, external rotation of the knee occurs by ____ rotation of the femur
internal
Motion is opposite
Generally, freedom of axial rotation _____ with greater knee flexion
increases
A knee that is flexed to 90° can perform about __°-__° of total axial rotation
40°-45°
_____ rotation range of motion generally exceeds _____ rotation by ratio of about 2 : 1
external
internal
From a tibial-on-femoral perspective the tibia rolls ____ and slides ____ during extension
anteriorly
anteriorly
In the same direction as the movement
From a femoral-on-tibial perspective the femur rolls ____ and slides ____ during extension
anteriorly (same direction as the movement)
posteriorly
In order to fully extend the knee about __° of external rotation is required. What is this called?
10°
“Screw-Home”Rotation of Knee
What characteristic of the medial femoral condyle helps direct tibia to its externally rotated and locked position
The fact that it is curved
For a knee that is fully extended to be unlocked, the joint must first _____ rotate.
internally
Which muscle internally rotates (unlocks) the knee?
popliteus
Once the knee is flexed, arthrokinematics of internal and external rotation involve primarily what motion between the menisci and articular surfaces.
spin
What are the functions of the MCL?
- Resists valgus (abduction)
- Resists knee extension
- Resists extremes of axial rotation (especially knee external rotation)
What are the functions of the LCL?
- Resists varus (adduction)
- Resists knee extension
- Resists extremes of axial rotation
What are the functions of the ACL?
- Most fibers resist extension (either excessive anterior translation of tibia, posterior translation of femur, or a combination thereof)
- Resists extremes of varus, valgus, and axial rotation
What are the functions of the PCL?
- Most fibers resist knee flexion (either excessive posterior translation of tibia or anterior translation of femur, or a combination thereof)
- Resists extremes of varus, valgus, and axial rotation
How do approximately 70% of ACL injuries occur?
through non-contact or minimal contact
What does the Sartorius muscle do at the hip and knee?
- Hip flexion, external rotation, and abduction
- Knee flexion and internal rotation
What does the Gracilis muscle do at the hip and knee?
- Hip flexion and adduction
- Knee flexion and internal rotation
What does the quadriceps femoris muscle do at the hip and knee?
- Hip flexion
- Knee extension
What does the popliteus muscle do at the knee?
flexion and internal rotation
What does the semimembranosus muscle do at the hip and knee?
- Hip extension
- Knee flexion and internal rotation
What does the semitendinosus muscle do at the hip and knee?
- Hip extension
- Knee flexion and internal rotation
What does the short head of the biceps femoris muscle do at the knee?
flexion and external rotation
What does the long head of the biceps femoris muscle do at the hip and knee?
- Hip extension
- Knee flexion and external rotation
What does the gastrocnemius muscle do at the knee and ankle?
- Knee flexion
- Ankle plantar flexion
What does the plantaris muscle do at the knee and ankle?
- Knee flexion
- Ankle plantar flexion
