Knee joint Flashcards
2 articulations of knee joint
Tibiofemoral (distal femur with proximal tibia) MAIN
Patellofemoral (distal femur with patella)
Type of joint that knee is
synovial
hinge (moves in 2 planes) flexion and extension
Stability changes in knee
when knee is extended = greater stability as there is a greater articulating surface (more contact between femur and tibia)
when knee is flexed - only round condyles are in contact
how is the knee joint supported?
ligaments
joint capsule
menisci
two menisci in knee
medial and lateral
what are menisci made of and what does this allow?
fibrocartilage
allows flexibility and they can change shape increasing congruity (surface contact) of the joint
other than increasing congruity, what is the other function of menisci?
Act as shock absorbers
Why are the medial and lateral menisci different?
medial menisci is connected to medial collateral ligament
medial menisci is less mobile than lateral
(lateral not attached to anything)
Extracapsular ligaments of knee
medial collateral
lateral collateral
Intracapsular ligaments of knee
anterior cruciate ligament
posterior cruciate ligament
where do the cruciate ligaments insert?
posterior - posterior tibia
anterior - anterior tibia
What do lateral collateral ligaments resist?
Varus strain (force pushing away from medial side)
what do medial collateral ligaments resist?
Valgus strain (force pushing towards medial side)
Bursa of the patella
Semimembranous Suprapatellar (above) Subcutaneous prepatellar (infront) Subcutaneous infrapatellar (below but superficial) Deep infrapatellar (below but deep) Subsatorial (pes anserinus)
Joint capsule of knee parts
Inner synovial membrane
Outer fibrous membrane
How is joint capsule strengthened medially?
Vastus medialis and lateralis
How is joint capsule strengthened laterally?
Collateral ligaments
How is joint capsule strengthened posteriorly?
Oblique popliteal ligament (semimembranosous expansion)
Quadriceps femoris
Anterior thigh
Vastus lateralis, intermedius, medialis, rectus femoris
Function: knee extension
Insertion: Quadriceps tendon, patellar ligament
Innervation: femoral nerve
Sartorius
Origin: anterior superior iliac spine
Insertion: pes anserinus
Function: Knee flexion
Innervation: femoral nerve
Hamstrings
Origin: Ischial tuberosity
Function: knee flexion
Innervation: all tibial sciatic nerve (apart from short head of biceps femoris - common fibular nerve)
Three muscles that insert onto pes anserinus
Sartorius
Gracillis
Semi tendonsous
(say grace after tea)
Gracilis
Origin: inferior ischiopubic ramus
Insertion: pes anserinus
Function: knee flexion
Innervation: obturator nerve
What does popliteus do?
Unlocks the knee - allows lateral rotation of femur
Innervation: Tibial nerve
