Knee Flashcards
What is the normal range of the internal angle of the knee?
185-190 // >190 = genu valga (knock knees) // <185 = genu vara (bow legged)
Where does the mechanical axis of the knee lie?
It begins at the head of the femur and runs straight through femur and tibia
Where does the anatomical axis of the knee lie?
It starts at the distal end of the neck of the femur and runs through the femur and tibia
How much larger is the medial tibial plateau when compared to the lateral tibial plateau?
As much as 50%
Lateral femoral condyle extends more in which direction?
Anteriorly
The medial femoral condyle extends more in which direction?
Distally
What is the closed pack position of the tibialfemoral joint?
Extension (and some external rotation)
What is the open pack position of the tibialfemoral joint?
25-30* of flexion - where most injuries happen
Genu Valgum increases the likelihood of OA on which side of the knees?
Lateral due to compression of lateral menisci/condyles
What is genu recurvatum?
Hyperextension of the knees
What are 3 possible causes of genu recurvatum?
Ligament laxity, weak quads, tight Achilles’ tendon
How many bursa does the knee joint capsule contain?
3 - suprapatellar bursa, subgastroc bursa, and subpopliteal bursa
Knee joint capsule fluid movement w/ extension
Moves from posterior to anterior and vice versa w/ flexion
The prepatellar bursa is associated w/ what condition?
Housemaid’s knee
Clergyman’s knee is associated with irritation of what bursa?
Superficial infrapatellar bursa
Where are the cruciate ligaments generally located?
In the fibrous layer of the joint capsule, but extrasynovial
LCL origin and insertion? Strengthened by what? Resists?
O: lateral femoral condyle
I: head of fibula
Strengthened by biceps femoris tendon
External rotation, becomes taut before MCL, this plays role in screw home mech
Also resists posterior displacement of tibia
When is LCL most taut? Lax?
Most taut in extension, most lax in flexion
MCL origin? Insertion?
O: medial aspect of medial femoral condyle
I: proximal tibia
Why does MCL heal faster than LCL?
MCL partial attaches to medial meniscus, it is apart of the joint capsule and receives nutrients from synovial fluid as well as blood
Posterior fibers of MCL orientation? Anterior fibers?
P: oblique
A: vertical
ACL origin and insertion
O: anterior medial surface of tibia
I: posterior lateral surface of femur w/in intercondylar notch
ACL comprised of 3 fibers
Anteromedial = most taut in flexion
Posterolateral = most taut in extension
Central
ACL resists (3) facilitates (1)
Anterior displacement of tibia on femur
Internal rotation
Valgus and varus forces @ knee
Facilitates normal glide/roll of femur on tibia
Terrible Triad
ACL, MCL, Meniscus
ACL commonly injured in what position of knee?
ACL more commonly injured in extension, closed-chain exercises are recommended for rehab
PCL origin, insertion, and bands?
O: posterior tibia in the intercondylar area (medial side of ACL)
I: Anteromedial femur on lateral aspect of medial femoral condyle
2 bands:
Anteromedial (taut in flexion)
Posterolateral (taut in extension)
PCL more commonly injured in what position of the knee?
Knee flexion (as opposed to ACL being more commonly injured in knee extension)
PCL resists what motion(s)?
Posterior displacement of tibia on femur
Internal rotation (especially at 90* of flexion)
Valgus/varus forces
Facilitates normal glide/roll
PCL mech of injury
Forceful posterior translation of tibia - “dashboard injury”
Oblique popliteal ligament origin and insertion + relation to popliteal fossa and artery
O: superior margin of intercondylar fossa of femur
I: posterior medial tibial condyle
Forms part of the floor of the popliteal fossa, popliteal artery rests on it
Oblique popliteal ligament mech of injury
Dashboard injury, fall on fully flexed knee so tibia hits first - same as PCL = forceful posterior translation of the tibia
Arcuate popliteal ligament origin and insertion
O:lateral posterior condyle of the femur
I: head of fibula
Ligaments of knee in flexion vs extension
Slack in flexion, taut in extension - screw home mech
Knee joint stability -Posterior Static
PCL, Oblique Popliteal, Arcuate Popliteal
Knee stability - Posterior Dynamic
Hamstrings, popliteus, gastrocnemius
Knee Stability - Medial Static
MCL, PCL
Knee stability - medial dynamic
Pens anserinus group (semitendinosis, gracilis, sartorious)
Knee stability - anterior static
ACL, MCL, LCL
Knee stability - anterior dynamic
quads, extensor retinacula
Knee stability - lateral static
LCL, IT band
knee stability - lateral dynamic
Biceps femoris // “not much”
menisci function (5)
Shock absorber (reduces joint reaction force by 40-60% during activity)
Increases articular surface area
Stabilization
Lubrication
Proprioception
Mechanism of injury for menisci
Axial rotation w foot planted - medial meniscus injured twice as much as lateral - Valgus force can make it worse, putting strain on MCL, posterior medial capsule and thus medial meniscus
What ligaments connect the medial and lateral anterior horns of the menisci?
Anterior transverse ligament
What ligaments root the menisci to their respective tibial plateaus?
Coronary (meniscotibial) ligaments
External attachments of medial meniscus (4)
ACL
MCL
semimembranosis (pulls posteriorly during flexion)
quads via meniscopatellar ligament (pulls anteriorly during extension)
External attachments of lateral meniscus (3)
PCL
Popliteus (pulls posterior during flexion)
Quad via meniscopatellar ligament (pulls anterior during extension)
lateral meniscus most mobile
Which area of menisci endure the most stress/force?
Posterior horns
Injuries to menisci (area and comparative likelihood)
Medial > lateral
Posterior > rest
How does ACL tear change osteokinematics of the knee?
More external rotation near full extension of the knee
Axial rotation at the knee - internal vs external
2:1 external to internal
Unlocking of screwhome mechanism involves? (Movement of bones/muscle?)
Either internal rotation of tibia on femur or external rotation of femur on tibia
Activation of popliteus
Why does LCL become taut before MCL when knee is extending?
LCL more posteriorly positioned
Which artery supplies the ACL?
Middle genicular
Which side of the patella is larger?
Lateral side - related to lateral femoral condyle extending more anteriorly
Which side of the patella does the odd facet lie?
Medial side
The patella increases moment arm for the quad group by what percentage?
50-60%
Patellafemoral pain disorders arise from what?
Lack of articular cartilage
Knee OA typically refers to which joint?
Tibiofemoral
Patellar shift w flex/ext?
Sits laterally at the start and end ranges, moves slightly medial in the middle of the range
Which direction is the articulating surface of the patella facing in ext? Flex?
Posteriorly in extension
Superiorly in flexion
What is circumferential displacement?
Term to describe the direction the articulating surface of the patella faces in flex, ext:
Faces posteriorly in extension
Faces superiorly in flexion
What does the articularis genu serve to do in relation to the suprapatellar bursa?
Pulls Suprapatellar bursa anteriorly to prevent it being pinched between femur and patella when the knee is moving from flexion into extension
The ________ surface of the patella articulates on the _______ surface of the femoral condyles in extension
INFERIOR surface of the patella articulates on the SUPERIOR surface of the femoral condyles
And vice versa as the knee moves into flexion
Proper alignment of the patella during movement is determined by (4)
Vastus lateralis, medialis
Lateral and medial retinaculum
Patellar stabilization (static?) (6)
Medial and lateral patellotibial ligaments
Medial and lateral patellofemoral ligaments
Medial and lateral retinacula
Patellofemoral disorders can typically lead to?
Disactiviation of quads
Q-angle definition, norm value?
Measurement of lateral line of pull of quads relative to the patella
15*
Abnormal Q-angle?
Greater than or equal to 20* = increased lateral pull of patella
Capsular pattern for knee
Greater loss of flexion
