Knee Flashcards
Normal knee alignment
5-10 degrees valgus
Genu Varum Characteristics (3)
- Genetics
- Foot alignment
- Tibial alignment
“bow-legged”
Genu Valgum Characteristics (3)
- Foot/Hip alignment (rearfoot/forefoot)
- Muscle Imbalance
- Ligament laxity
“knock-knee”
Genu Recurvatum Characteristics
hyperextension of knee > 10 deg
What structures resist genu recurvatum?
Posterior knee capsule
Knee flexor muscles
Causes of Genu Recurvatum (3)
- Poor posture
- Neuromuscular imbalance
- Fixed plantar-flexed foot
Closed Chain- Pronation
Calcaneal eversion Talar pf + adduction Tibial Internal Rotation Knee Flexion Femoral Internal Rotation Hip Flexion
Closed Chain- Supination
Calcaneal Inversion Talar df + abduction Tibial External Rotation Knee Extension Femoral External Rotation Hip Extension
What is the Screw-Home Mechanism?
locking the knee in full ext.
~10 deg tibial external rotation
increases joint congruity and stability
What is open chain for tibia on femur?
internal rotation
What is closed chain for femur on tibia?
external rotation
What mechanics drive the Screw-Home Mechanism?
- Shape of medial femoral condyle
- Passive tension in ACL
- Lateral pull of quads
What is the arthrokinematics rule for knee?
Tibia (concave) moves on Femur (convex) = Roll + Glide are in SAME direction
During knee extension, _________ tibial glide on femur
anterior
During knee flexion, __________ tibial glide on femur
posterior
Properties of MCL
superficial + deep layers
capsule + medial meniscus
Functions of MCL
resist valgus + extension forces at knee
MOI of MCL
Excessive valgus force w/ foot planted
Severe hyperextension
Clip injury (rec sports)
Properties of LCL
less broad
one layer
Functions of LCL
resist varus force + extension forces at knee
MOI of LCL
Excess varus force w/ foot planted
Severe hyperextension
Properties of ACL
lateral medial tib to medial lateral fem
2 bands twist:
- Ant med
- Post lat
Functions of ACL
Stability (extension)
Arthrokinematics
Proprioception
MOI of ACL
Hyperextension
Excessive valgus w/ foot planted
Excessive knee rotation
Decelerating, pivoting
Open Chain of ACL
prevents excessive anterior of tib on femur bc quads pull
Closed Chain of ACL
prevents excessive posterior of femur on tib
Properties of PCL
Posterior condylar tib to lateral medial fem
thicker than ACL
Functions of PCL
Arthrokinematics
Resist flexion, extreme valgus, varus
Taut w/ greater flexion
MOI of PCL
Falling on flexed knee (ankle pf)
Tibia forced posteriorly, femur forced anteriorly (dash injury)
Rotation, varus/valgus w/ foot planted
Open Chain of PCL
prevents excessive posterior of tib on fem
Closed Chain of PCL
prevents excessive anterior of fem on tib
Meniscus Characteristics
Fibrocartilaginous discs
Thicker on edges
Shift during knee mvmt
Meniscus Functions
Shock absorption
Stabilization
Guides of arthrokinematics
Lubricates articular cartilage
Medial Meniscus Characteristics
C-shaped
attaches to MCL and capsule
6 mm
Lateral Meniscus Characteristics
O-shaped
attaches to capsule
12 mm
During knee flexion, meniscus moves ____?
anterior
During knee extension, meniscus move____?
posterior
When externally rotating tibia, lateral meniscus moves______?
anteriorly
When internally rotating tibia, lateral meniscus moves______?
posteriorly
When externally rotating tibia, medial meniscus moves______?
posteriorly
When internally rotating tibia, medial meniscus moves______?
anteriorly
What are MOI of meniscus?
forceful compressions + axial rotation (w/ knee flexed)
Med Men when flexion, axial rotation, valgus
Patellofemoral joint function
protect tibia and fibula joint
mechanical advantage of quads (movable pulley)
Patellar Positions
Medial/Lateral Shift/Glide Medial/Lateral Tilt Anterior/Posterior Tilt Internally/Externally Rotated Baja/Alta
Q-Angle Normal Values
0-15 deg
Average Q-Angle Values
13-15 deg
What factors affect Q-angle?
Tibial rotation Femur rotation Width of pelvis Genu valgum Hip adduction
Are there more or less joint loading forces at patellofemoral joint when knee flexes?
More compressive forces
Muscle force from quads
What activities increase joint compression force at patellofemoral joint?
Walking- 1.3x body weight
Climbing stairs - 3.3x body weight
Running- 5 to 6x body weight
Deep squat- 7.8x body weight
Patellofemoral Pain Syndrome
abnormal tracking of patella
anterior knee pain
subluxation of patella (severe case)
