knee Flashcards
what is the knee joint?
- synovial joint
- connects femur, tibia and fibula
what are the functions of the knee?
- supports body weight
- transmits force to provide movement
- stability
- mobility
what movement occurs at the knee and their angles
flexion (140) extension (0) medial (25) and lateral (40) rotation
what is the joint between femur and tibia?
tibiofemoral
describe tibiofemoral joint
synovial bicondylar joint between femoral condyles and tibia
what movement is allowed in tibiofemoral joint?
- movement in two planes around two axes as bi- axial
where are the femoral condyles and describe appearance
- distal end of femur
- covered in hyaline cartilage
what condyle is longer? what shapes are they?
- lateral profile longer than medial
- convex so like a circle
where are the tibia condyles found?
- proximal end of tibia
what are the tibia condyles covered by?
- cartilage layer
- menisci
describe medial surface of tibia condoyle
- large
- oval
describe lateral surface of tibia condyle
- smaller
- circular
what are menisci?
- fibrocartilage discs
- semi lunar
what are the four functions of knee menisci
- increases congruency between articular surfaces
- absorbs shock
- assists weight bearing across joint (transfers/ absorbs)
- facilitates accessory movements
what is the medial collateral ligament?
extra-capsular ligament that is a broad flat band,10cm long
where does medial collateral ligament originate and insert?
origin= medial epicondyle of femur
insert= tibia condyle
what does medial collateral ligament prevent?
- valgus displacement, whereby knee knock position= adduction of a joint that doesn’t usually adduct
what is lateral collateral ligament?
extra capsular, strong short thin cord
what is lateral collateral ligament origin and insertion?
origin= lateral epicondyle of femur
insert= head of fibula
what does the lateral collateral ligament prevent?
varus displacement= bow legged action; adduction when not meant to
what is the anterior cruciate ligament?
intracapsular ligament that crosses over and splits into two bundles
where does anterior cruciate ligament originate and insert?
origin= posteromedial surface of lateral femoral condyle
insert= anterolateral tibial spine
what does anterior cruciate prevent?
anterior tibial displacement whereby tibia moves forwards onto femur
what is the posterior cruciate ligament ?
intracapsular ligament that splits into two bundles
what is the origin and insertion of posterior cruciate ligament?
origin= anterolateral surface of medial femoral condyle
insert= posterior intercondylar area
what does posterior cruciate ligament prevent?
posterior tibial displacement where something strikes front of knee and pushes tibia back
what is the name of the joint between patella and femur?
patellofemoral
what type of joint is patellofemoral?
- synovial saddle as both have concave and convex parts
what bone is the patella?
largest sesamoid bone in body
- bone embedded in quadriceps tendon
describe the patellar surface of femur
- cartilage covered surface
- groove articulates with a ridge on patellar surface
what are the functions of patella?
- reduces friction between quadriceps tendon and femoral condyles (less damage)
- anatomic pulley as quadriceps can pull round corner to pull tibia and extend the knee
what is the shape and colour of patella?
- oval shaped
- shiny due to hyaline cartilage
what separates medial and lateral areas ?
- what is up and down sections?
- what is superior to inferior?
vertical ridge; convex= up/ down
concave= superior to inferior
what area is larger?
lateral area
where is quadriceps tendon?
- on top of patella
where is patella tendon and where does it insert?
- below patella
- inserts into tibial tuberosity and allows insertion of thigh muscles
what is the patella tendon continuous with?
- quadricep femoris tendon
what occurs during close packed position? give some properties
- extension as patella moves up proximally
- no rotation allowed
- stable and congruent due to maximum contact
- ligaments become taut
what does loose packed position allow?
- flexion as patella moves distally on femur
- allows some rotation
what is a joint capsule?
fibrous bag made of dense irregular connective tissue that holds synovial fluid
what is the capsule reinforced by?
- number or ligaments and tendons e.g. collateral ligaments, expansions coming off quadriceps
why is the knee classed as incomplete? what is it plugged by?
- hole at the front
- plugged by patella and patella tendon
what are bursaes?
fluid filled sacs to reduce friction e.g. skin doesn’t rub on patella
what does pes anserinus bursa stop?
- medial collateral ligament rubbing on three tendons
what bursa is above patella and under quad femoris tendon?
-suprapatellar
what bursa sits on top of patella?
prepatellar
what bursa sits underneath patella tendon ?
intrapatellar
what is the knee locking mechanism?
- femur rotates to complete movement i.e. in last 30 degrees of full extension femur medially rotates
why does the knee locking mechanism occur?
- inequality of articular surface of femur condyles
what happens during extension?
- tibia rolls posteriorly, elongates PCL and its pull on tibia causes it to glide anterior
what happens during extension?
- tibia rolls anteriorly, elongates ACL and its pull so tibia glides posteriorly
what occurs in unlocking?
- lateral rotation of femur
- use of popliteus (back of knee)
what is passive insufficiency?
muscle lengthened but limited movement at one/ more joints it crosses
what is active insufficiency?
decreased tension and inability to generate force in multi- joint muscle when in shortened position as no binding sites free
where do knee flexors sit?
- posterior
where do knee extensors sit?
- anterior
- above knee
origin, insertion and action of gastrocnemius
o- femoral condyles
I- posterior calcaneus
A- flexion
lateral head goes to lateral condyle whereas medial head starts at medial condyle
origin, insertion and action of biceps femoris
o- short head= Linea aspera; long= medial ischial tuberosity
I- fibula head
a- flexor and lateral rotator
origin, insertion and action of sartorius
o -anterior superior iliac spine (ilium)
I= pes anserinus
a= flexor and medial rotator
origin, insertion and action of rectus femoris
o- (long) anterior superior iliac spine (short) groove above acetabulum
I= patella
a= extensor
origin, insertion and action of vastus lateralis
o= greater trochanter
I= tendon of rectus femoris and patella
A= extensor
Insertion, origin and action of vastus medialis
I= medial line of Linea aspera and medial supracondylar line
I= medial patella
A= extensor
Origin, insertion and action of vastus intermedius
O= upper anterior and lateral surface of femur
I= rectus femoris tendon and base of patella
A= extensor
Origin, insertion and action of tensor fascia Lata
O= lateral anterior iliac crest
I = iliotibial band
A= extensor; stabilises knee
Origin, insertion and action of semitendinosus
o= lower ischial tuberosity
I= pes anserinus
a= medial rotator
Origin, insertion and action of semimembranosus
o= upper ischial tuberosity
I= medial tibial condyle
A= medial rotation
Origin, insertion and action of gracilis
o= inferior pubic ramus
I= pes anserinus
A= medial rotation
Origin, insertion and action of popliteus
o= lateral femoral condyle
I=posterior tibia
A= medial rotation
what are the functions of popliteus ?
- pulls lateral meniscus backwards to stop it getting trapped in flexion
-allows accessory movements; stability in joint capsule
