Biomechanics Knee Flashcards
What type of joint is the knee?
Modified ginglymus joint (Hinge joint)
What bones are involved in the knee?
Femer, Tibia, and Patella
How many joints are involved at the knee
2
Tibiofemoral
Patellofemoral
What is the Q-angle?
(Alignement at the patellofemoral joint)
ASIS to midpoint of the patella and a line to the tibial tuberosity
What does a smaller Q-angle do?
May increase medial knee pressure
What does a larger Q-angle do?
May increase lateral knee pressure
What’s a normal Q-angle?
185-190 degrees
What is Genu Valgum?
Knees coming in.
Normally 5-10 degrees
What is excessive genu valgum?
190 degrees
What side of the knee can genu valgum increase compression?
Lateral Side
Whats genu varum?
(Bow legged)
Knee angle less than 170 degrees
What side of the knee has an increased compression force in genu varum?
Medial side
What is genu recurvatum?
Extension beyond 10 degrees from neutral
What are some functions of the tibiofibular joint?
Dissipation of torsional stresses applied at the ankle
dissipation of lateral tibial bending movements
tensile weight bearing
What type of joint is the tibiofemoral joint?
Double condyloid synovial joint
How many degrees of freedom does the tibiofemoral joint have?
3
What causes lateral tracking of the patella?
increased forces of ITB
Bowstringing
Lateral patellar retinacular fibers
What causes medial tracking of the patella?
VMO
Raised lateral facet
Medial patellar retinacular fibers
What would an external force on the knee create and what effects will it have on the knee and patella tracking?
(Valgus force)
ER of femur
IR of tibia
Create increased tension at QT and PT, increase bowstringing
Will increase the lateral displacement of patella
Where does the ACL run?
Anterior tibia to posterior, lateral femoral condyle
What’s the ACL’s function?
Most effective in extension
resists excessive tibial anterior slide/translation
resists excessive femoral posterior slide/translation
resists excessive axial rotation, varus and valgus forces
What can cause injuries to the ACL?
Large valgus force with foot planted
Large axial rotation force applied while foot is planted
Combination of the two
Severe hyperextension
Where does the PCL run?
Posterior tibia and runs in a proximal, medial, and anterior direction attaching the medial femoral condyle
What is the function of the PCL?
Most effective in flexion
resists excessive tibial posterior slide/translation
resists excessive femoral anterior slide/translation
resists excessive axial rotation, varus and valgus forces
What causes injuries to the PCL
Falling on fully flexed knee w/ proximal tibia striking first
Force posterior translation of tibia
Worse with increasing flexion
Rotation, varus, and/or valgus force applied with foot planted
severe hyperextension with gapping to posterior side
Where does the MCL run?
Attach proximally to the medial femoral epicondyle and distally at the shaft of the tibia and tibial condyle
Which portion of the MCL attaches to the medial meniscus?
Deep portion
What is the function of the MCL?
Resist valgus force
resist knee extension
reinforce medial capsule
prevents ER of the leg (with knee extended)
How do you injure the MCL?
Valgus producing forces with foot planted
Severe hyperextension
Where does the LCL run?
lateral epicondyle of femur to head of fibula
What is the function of the LCL?
resist varus forces resists knee extension prevent ER of the leg (with the knee extended) reinforce lateral capsule reinforce posterior-lateral capsule
How do you injure the LCL?
varus producing force with foot planted
severe hyperextension
How is the anterior portion of the knee capsule reinforced?
Connective tissue:Patellar tendon
Patellar retinacular fibers
Muscular-Tendinous: Quadriceps
How is the lateral portion of the knee capsule reinforced?
Connective tissue
LCL, lateral retinaculum, IT band
Muscular-tendinous
Biceps femoris, popliteus, gastrocnemius
How is the posterior portion of the knee capsule reinforced?
Connective tissue
Oblique popliteal ligament, arcuate complex
Muscular-tendious
gastrocnemius, hamstrings
How is the posterior-lateral portion of the knee capsule reinforced?
Connective tissue
Arcuate complex, LCL
Muscular-tendinous
popliteus
How is the medial portion of the knee capsule reinforced?
Connective tissue
retinaculum, MCL, posterior-medial capsule, posterior oblique
Muscular-tendinous
pes anserine
What are the meniscus?
Fibrocartilaginous discs
located directly between the femoral condyles and the tibial plateau
What’s the function of the meniscus?
deepen surface of the tibia
makes a concavity atop the tibial plateau
shock absorbers
Which meniscus is bigger?
Medial
Medial tibial plateau is bigger
What attaches to the medial meniscus?
MCL
Semimembranosis (posteriorly)
Which meniscus has more mobility?
Lateral meniscus
What attaches to the lateral meniscus?
Popliteus (posteriorly)
Which meniscus abosorbs more stress?
Lateral 70% of load
Which way does the menisci move during knee extension/flexion?
Extension: Moves anteriorly with the tibia
Flexion: Menisci moves posteriorly with the tibia
What causes meniscal injury?
Axial rotation, valgus force most common mechanisms
50% of ACL tears involve meniscus
Correlates with early onset osteoarthritis
Where’s the infrapatellar fat pad and what does it do?
Between the patellar tendon and the tibia
Very sensitive
helps reduce friction in the knee
Name the knee extensors
Quadriceps
Articularis genu
Name the knee flexors
Hamstrings Sartorius Gracilis Popliteus Gastrocnemius Plantaris
What makes up the pez anserine?
Sartorius
Gracilis
Semitendinosis
What is active insufficiency?
Extreme shortened muscle results in decreased motor recruitment (hip is extended, and knee is fully flexed, hamstring is shortened)
What is Passive insufficiency?
Tightened/lengthened muscle causes decreased muscle contraction (Hip is flexed, knee is extended, Hamstring fully lengthened)
