Knee and thigh continued Flashcards
The knee joint has two articulations. What are they?
Tibiofemoral (condyles of each)
Patellofemoral (patella and trochlear groove)
Functions of the patella?
- Acts as a fulcrum for the quadriceps muscle, increasing its efficiency. Thus increases the power of knee extension (quadriceps).
- Protection for anterior knee
- Stabilises the knee joint, reducing frictional forces placed on femoral condyles
Which blood vessels supply the knee?
Which artery do they branch from?
What do they compensate for?
genicular arteries which make up the genicular anastomoses (circular network)
femoral and popliteal artery
narrowing of the popliteal artery during knee flexion
Where is the popliteal artery?
Continuation of the femoral artery below the adductor hiatus (gap between adductor magnus and femur).
Functions of the tibial menisci?
- Deepen the articular surface of the tibia to increase stability of knee joint
- Act as shock absorbers; increase surface area to further dissipate forces
Damage to the medial collateral ligament can also cause tearing of ____?
What could damage the medial collateral ligament? Explain.
The medial meniscus because the MCL adheres to it
Excessive lateral displacement of the tibia (valgus angulation). The medial collateral ligament prevents outward/ Lateral angulation of the tibia (vaLgus angulation).
Which tibial menisci is larger?
What shape are they?
How are they connected anteriorly?
Medial
Both C -shaped (crescentic)
Transverse ligament of the knee
What are the ligaments of the knee?
- cruciate ligaments
- collateral ligaments
- oblique popliteal ligament
(inserts on medial tibial condyle)
How does blood flow to the tibial menisci change with age?
Reduces so that the central meniscus is avascular by adulthood which impairs healing
What movement does the anterior cruciate ligament resist?
- medial rotation of the tibia relative to the femur
- anterior translation
Where do the cruciate ligaments insert on the femur?
A- lateral border of intercondylar fossa
P- medial border and roof of intercondylar fossa
Main functions of the posterior cruciate ligament? (2)
- prevents posterior dislocation of the tibia on the femur
- Main stabiliser of the weight-bearing flexed knee; prevents the femur sliding anteriorly off the edge of the tibia when walking down stairs/ a slope
The joint capsule of the knee is deficient where?
What does this allow?
The knee capsule is strengthened medially and laterally by which muscles fibres?
Anteriorly
Allows synovial membrane to extend upwards, forming the suprapatellar bursa
Fibres of the vastus medialis and lateralis (medial compartment of thigh).
What do the collateral ligaments do?
Which is stronger?
- Stabilise the hinge movement
- Prevent excessive lateral/ medial angulation of tibia on the femur (valgus/ varus angulation)
Lateral bc its reinforced by the iliotibial tract and works as 1/3rd of the posterolateral corner
Which knee ligament resists valgus angulation of the tibia?
And which resists varus?
Medial collateral ligament
Lateral collateral ligament
What is the posterolateral corner of the knee?
Three ligaments on the lateral side of the knee which extend over the joint.
- lateral collateral ligament
- popliteus muscle tendon
- arcuate ligament
How many bursae are there in the knee?
Where is the subsartorial/ pes anserinus bursa?
6
Between insertion of the pes anserinus tendon (anteromedial surface of tibia) and the medial condyle
By what mechanism does the knee passively lock?
Which muscles can now relax?
‘scre home mechanism’,
5 degree medial rotation of the femoral condyles on the tibial plateau
thigh and leg muscles without destabilising the knee joint
How does the (passively) locked knee unlock?
Popliteus muscle contracts to cause 5 degree lateral rotation of femur on the tibial plateau
During knee extension, the patella is naturally inclined to displace ____y?
Why?
laterally
Q angle between direction of pull from quadriceps muscle and patellar ligament