knee Flashcards
what 3 bones form the knee joint
- distal femur
- proximal tibia
- patella
what are the 2 prominences found at the lower end of the femur
lateral and medial femoral condyles
femoral condyles are continuous superiorly with the femoral shaft
(curved from front to back)
what structure separates the lateral and medial condyles?
deep notch known as the
- intercondylar fossa/notch
what is the inferior, anterior and posterior aspect of the femoral condyles covered in
hyaline cartilage
what area do the femoral condyles articulate with
medial and lateral articular facets on the tibial plateau
how does the structure of the medial and lateral tibial plateau differ
medial tibial plateau is concave
lateral tibial plateau is relatively flat
what separates the medial and lateral tibial plateeau
intercondylar eminence
- this has 2 bony projections, the medial and lateral tibial spines
what do you call the joint connecting the patella and femur
patellofemoral joint
what do you call the articulating joint between the fibula and tibia
tibiofibular joint
what is a cruciate ligament
ligaments that cross each other
what are the 2 cruciate ligaments found in the knee
- anterior cruciate ligament
- posterior cruciate ligament
where is the ACL AND PCL attached to in the knee
ACL is attached to anterior intercondylar area of the tibial plateau
PCL is attached to the posterior intercondylar area of the tibial plateau
how does the anterior cruciate ligament attach to the knee
- runs from medial surface of lateral femoral condyle to facet on medial part of anterior intercondylar area of tibial plateau
what is the function of the ACL
- resist posterior displacement of the femur on tibia (or anterior displacement of tibia on femur)
how does the posterior cruciate ligament attach to the knee
- runs from lateral surface of medial femoral condyle to facet in the posterior intercondylar area of the tibial plateau.
- also attaches to the posterior horn of the lateral meniscus
what is the function of the PCL
resist anterior displacement of the femur on the tibia
what is the lateral /medial meniscus of the knee
one of two semilunar (circular) fibrocartilaginous structures in the knee joint that act as shock absorbers, enhance joint stability and aid in the distribution of synovial fluid.
what is the strongest ligament in the knee
posterior cruciate ligament
what are collateral ligaments
- go taut when knee joint is extended and therefore promotes media-lateral stability in extension position
what are the 2 collateral ligaments in the knee
- lateral fibular collateral ligament
- medial tibial collateral ligament
how does the lateral (fibula) collateral ligament attach to the knee
- runs from the lateral surface of the lateral femoral condyle to the head of the fibula
(lies outside knee joint capsule)
how does the medial (tibial) collateral ligament attache to the knee
- runs from medial surface of medial femoral condyle to medial surface of tibia
- posterior part blends with capsule of knee joint and partly fuses with medial edge of the medial meniscus
what are the 2 menisci / semilunar cartilages of the knee
- medial and lateral meniscus
what are menisci + what is their function
- fibrocartilaginous structures situated in capsule of knee joint
- distribute weight more evenly through knee joint
- act as shock absorbers
describe the structure of the menisci and how they articulate with the femur
- upper surface of meniscus is concave and articulates with peripheral part of overlying femoral condyle
- lower surface is flat and rest not he articular facet of tibial plateau
why is the cross section of the menisci wedge shaped (thicker then thinner going in)
- as they are attached to the rims of the articular facets on the tibial plateau, the attached border is thick whilst the inner free border is thin
what are the horns of the meniscus attached to
non-articular intercondylar area of the tibial plateau
what 4 muscles of the quadriceps join to form the quadriceps tendon
- rectus femoris
- vastus lateralis
- vastus medialis
- vastus intermedius
what structure of the knee does the quadriceps tendon attach to
upper border of patella
where does the patellar tendon attach to in the knee
from the inferior pole of the patella to the tibial tuberosity
what is the role of the quadriceps tendon and patellar tendon
- control the position of the patellar tracking in flexion and extension of the knee
what do you call the fat containing space between the patellar tendon and anterior aspect of the knee joint
- infra patellar or Hoffa’s fat pad
how is a lateral knee xray taken for a trauma patient
- using horizontal beam
what is a lateral view of the knee useful for
- detaching knee joint effusions which can occur as a result of meniscal or ligamentous injury
- also arthritis, gout or infection
what do you call an effusion in the supra-patellar region of the knee joint containing fat and blood
- lipoheamarthrosis
what might cause a lipoheamarthorosis to occur
- intra-articular fracture where bone marrow fat leaks out into the joint
why can a fat fluid level be seen on lateral radiograph
because fat floats onto of blood in joint and is more Lucent than soft tissue or fluid
what is a skyline/axial view of the knee
xray taken for suspected fractures or dislocations of the patella
what imaging modality is best for assessing internals of tissue injuries to muscles, ligaments, tendons, menisci and cartilgae
MRI
what is a supracondylar fracture and what likely causes this
- fractures of the distal 3rd of the femur, just above the level of the femoral condyles
- severe trauma such as car crash (as femur is strongest bone)
what is the typical structure of a femoral condylar fracture (both)
- T or Y shaped
- vertical fracture line passing through intercondylar notch
what likely causes a tibial plateau fracture
- force to medial/lateral side of weight-bearing knee e.g ski jump or falling from height
which nerve can be associated with fractures of the proximal fibula
peroneal nerve (which winds around the fibular neck)
which ligaments can be damaged as a result of tibial plateau fractures
anterior and posterior collateral ligament
what can cause a patella fracture
- direct trauma to anterior aspect of knee
or - sudden powerful contraction of quadriceps muscle
vertical patella fractures are usually undisplaced
patella fractures are hard to see on ap and lateral knee projections, hence what view is needed
skyline
which direction does the patella usually dislocate to
laterally
what 2 injuries can happen following dislocation of patella
- haemarthrosis and residual patella displacement
- osteochondral fracture of medial patella or anterior lateral femoral condyle
if there is bone marrow contusion (bruising and oedema) in the medial patella and anterior lateral femoral condyle, how does this show up on MRI
- seen as bright area on MRI (high signal)
how might you tell there is rupture of the patellar tendon on plain radiograph
- abnormally high position of the patella and small avulsion fractures of inferior patella
how might you tell there is rupture of the patellar tendon on MRI
- retraction and thickening of remnant patellar tendon
- haemorrhage and oedema may also be seen
what is patellar tendinopathy (jumpers knee)
syndrome of overuse of the patellar tendon affecting the proximal tendon , resulting in localised pain and swelling directly inferior to the patella
how do you spot patellar tendinopathy on mri
focal thickening of proximal patella tendon despite being intact
how can you spot a quadriceps tendon rupture on radiograph
- low-lying patella with soft tissue swelling above
which direction is the dislocation of the tibia most common in
anterior
for anterior dislocation of the tibia, which ligament will have ruptured
anterior cruciate ligament
for medial dislocation of the tibia in relation to the femur, which ligament will have ruptured
medial and lateral collateral ligament
- supported by presence of avulsion by MCL and LCL
which ligaments are most likely to become injured and why not the others
- medial collateral and anterior cruciate
- PCL is strongest ligament, thicker and stronger than ACL
-LCL is stronger than MCL as its part of complex structures that stabilises lateral aspect of knee joint
whats the difference between strain and sprain
sprain = ligament injury
strain = muscle or tendon injury
what is o’donoghue’s triad
(1) rupture of the medial collateral ligament,
(2) damage to the medial meniscus, and
(3) rupture of the anterior cruciate ligament”
what is a vulgus injury
bone at the knee joint is angled out and away from the body’s mid-line
(leg bends laterally in easy words)
what are signs of ACL injury
- pivot shift injury
- external rotation and vulgus stress in flexed knee
what are 3 signs that may be seen on plain film radiograph of knee proving ACL injury
- avulsion of intercondylar eminence of tibia
- anterior displacement of tibia with respect to femur
- segond fracture (an avulsion type fracture of the lateral proximal tibia at the attachment of the anterolateral ligament)
how might a PCL injury occur
falling on an object or dashboard impact in car crash
- PCL injury caused by tibia forced backwards
how can injury to menisci happen
rotational stress of flexed, weight-bearing knee or sudden knee extension movement
why is the medial menisci most likely to be injured
- lateral menisci is more mobile hence less susceptible to damage
how is the ‘bucket handle tear’ of a menisci formed
- vertical circumferential tear of meniscus
- central/free edge gets displaced towards central of knee
what issues come about with the bucket handle tear of the mensici
- locked knee with elastic block to full exertion of the joint
what are 2 other types of menisci tears beside the bucket handle
- vertical radial
- horizontal oblique tear
as the inner 2 3rds of the menisci are avascular , theres usually no haemoarthorsis to cause swelling if only central substance of meniscus is torn longitudinally but what type of tearing could cause it
- peripheral tear
what does a meniscal tear look like on MRI
- bright, fluid filled lines with black menisci
or - incomplete menisci with bits missing (bucket handle tear)
the most common sit of patella tendon rupture is where
proximal patellar tendon
how many articulations does the knee joint have and what are they
3
- lateral condyle of femur and lateral tibial plateau
- medial condyle of femur and medial tibial plateau
- patella and patella surface of femur
medial meniscus attaches to medial collateral ligament but the lateral meniscus doesnt attach to the lateral collateral ligament
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