anatomy of knee Flashcards
what type of joint is the knee?
bicondylar hinge joint
what is the function of the locking mechanism of the knee?
reduces the amount of energy required when the knee is extended
how does the shape f the femur assist in the locking and rolling mechanisms of the knee?
locking: the most inferior aspect of the femur is flat, which allows for stabillity when the knee is extended
flexion: during flexion the post possterior part of the femur is involved , this is ronund and allows rolling of the joint
what are the 3 things that allow locking of the knee?
- shape- shape of the femur allows the flat surface of the femur to be in contact with the tibia during extention, and this is more stable
- rotation- femur medially rotates in relation to the tibia during extention which tightens the ligament of the knee
- centre of gravity- centre of gravity is right through the patella, which maintains the knee in extention
what is the importance of the femoral angle?
- is the angle between the mechanical axis and atomical axis (15degrees)
- adducts the femur so it sits below the pelvis, which is critical for weight bearing
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what is a varus deformity?
- decreased q angle
- because of medial displacemnt of ibia
- results in bow-leggedness
- results in joint degeneration
what is a valgus deforminty?
- increased q angle
- later displacement of femur in relationto tibia
what are the extracapsular ligaments of the knee?
medial collateral
lateral collateral
what are the intracapsular ligaments of the knee?
- anterior cruciate
- posterior cruciate
what is the fiunction of the lateral fibular collateral ligament?
- round cord
- prevents medial displacement of tibia
what are is the function of the medial collateral ligament?
- broad flat band
- reinforces the joint capsule
- prevents lateral displacement of tibia (valgus deforminty)
what are the functions of the cruciate ligaments?
anterior cruciate ligaments- prevents anterior displacement of tibia on femur
posterior cruciate ligaments- prevents posterior displacement of tibia on femur
both maintain the femur against the tibia- so one ligament is always tense
how do the cruciate ligaments pass?
- posterior cruciate- upwards and forward medially
- anterior cruciate ligament- upwards annd backwards laterally
why can you laterally rotate your flexed knee more than you can medially rotate it?
- medial rotation tightens ligaments so rotation is just 10 degrees
- lateral rotation unwinds the ligaments so you can rotate 60 degrees
how does ACL become injured?
- caused by sharp twisting of the knee
- weaker than PCL soinjured more easily
what is the lachman test used for?
- to check for ACL injury
- Patient in supine position with knee bent 20-300 of flexion
- Move tibia anteriorly and posteriorly while maintaining position of femur
- Laxity during this manoeuvre indicates anterior cruciate ligament injury
when is the PCL particularly important?
- its the principal stabiliser of flexeed knee
- so especially important when walking down hill
what are the menisci of joint?
cresent shaped plates of fibrocartilage
what are the functions of the menisci?
- deepen the articulating surfaces for stability
- act as shock absorbers
- provide smooth viscus film for joint
what is the unhappy triad?
rupture of…..
- ACL, MCL and medial meniscus attatched to MCL
occurs during contact sports when there has been…
- twisting of a flexed knee and a blow to the lateral side
which muscle prevents lateral tracking of patella?
because of the abduction of the femur and the action of rector femoris there is a tendency for patella to tract laterally when walking
- vastus medialis counteracts this lateral pull
what are the functions of the patella?
- protects quadraceps tendon from stress during locomotion
- smooth oval facet of posterior surface for articulation with femur
what injuries can you get to the extensor mechanism?
- rupture of quadraceps tendon or patellar ligament
- fracture of patella
- disslocation of patella
which muslce is responsible for unlocking the knee?
Popliteus unlocks knee joint
- Laterally rotates femur on tibia when foot is on ground
