lower extremity - the knee Flashcards
what is the Q-angle?
angle between the line of action of quadriceps & line of action of patellar tendon
what are the joints of the knee?
- tibiofemoral joint
- patellofemoral joint
- proximal tibiofibular joint
what kind of joint is the tibiofemoral?
biondyloid joint
what kind of joint is the patellofemoral joint?
trochlear joint
what kind of joint is the proximal tibiofibular joint?
planar joint
what are the roles of the proximal tibiofibular joint?
- very small weight bearing role
- very small role in motion
what are the functions of the patella?
- anterior knee protection
- provides better mechanical advantage for quadricep action on tibia
importance of mechanical advantage in patella function?
- insertion angle would be near 0° in extension
- resulting it in being impossible to produce force
what are the four ligaments in the knee?
- medial collateral ligament (MCL)
- lateral collateral ligament (LCL)
- anterior cruciate ligament (ACL)
- posterior cruciate ligament (PCL)
what are the extra capsular & extra articular ligaments?
- medial collateral ligament (MCL)
2. lateral collateral ligament (LCL) `
what are the intra articular & extra synovial ligaments?
- anterior cruciate ligament (ACL)
2. posterior cruciate ligament (PCL)
general functions of anterior & posterior cruciate ligaments?
- provide multiple planar dynamic knee stability
- guides natural arthrokinematics
- contributes to proprioception in knee
what ligament is the primary restraint for valgus force?
medial collateral ligament (MCL)
what are the secondary restraints for valgus force?
- posterior medial capsule
- anterior & posterior cruciate ligaments
- lateral joint contact
- lateral meniscus compression
- medial retinacular fibres
- medial head of gastrocnemius
- tendons of sartorius, gracilis, & semitendinosus
what ligament is the primary restraint for varsus force?
lateral collateral ligament (LCL)
what are the secondary restraints for varus force?
- posterior-lateral corner of knee
- iliotibial band
- biceps femoris tendon
- medial joint contact
- medial menisus compression
- anterior & posterior cruciate ligaments
- lateral head of gastrocnemius
what is included in the posterior-lateral corner of the knee?
- posterior-lateral capsule
- arcuate popliteal ligament
- lateral collateral ligament (LCL)
- popliteofibular ligament
- popliteus tendon
functions of medial collateral ligament & posterior-medial capsule
- resists valgus (abduction)
- resists knee extension
- resists extremes of axial rotation (especially external knee rotation)
common injury mechanisms of medial collateral ligament & posterior-medial capsule
- valgus producing force with planted foot
- severe knee hyperextension
functions of lateral collateral ligament
- resists varus (adduction)
- resists knee extension
- resists extremes of axial rotation
common injury mechanisms of lateral collateral ligament
- varus producing force with planted foot
- severe knee hyperextension
functions of posterior capsule
- resists knee extension
- oblique popliteal ligament resists knee external rotation
- posterior-lateral capsule resists varus
common injury mechanism of posterior capsule
hyperextension or combined hyperextension with external knee rotation
functions of anterior cruciate ligament (ACL)
- most fibers resist extension
- resists extremes of varus, valgus, & axial rotation
common injury mechanisms of anterior cruciate ligament (ACL)
- large valgus-producing force with firmly planted foot
- large axial rotation torque applied to knee with firmly planted foot
- severe knee hyperextension
functions of posterior cruciate ligament (PCL)
- most fibers resist knee extension
- resists extemes of varus, valgus, & axial rotation
common injury mechanisms of of posterior cruciate ligament (PCL)
- falling on a fully flexed knee resulting in proximal tibia striking the ground first
- any event causing forceful posterior tibial translation or anterior femoral translation, especially with fully flexed knee
- large axial rotation or valgus-varus applied torque to knee with firmly planted foot & flexed knee
- severe knee hyperextension
what does severe knee extension involving posterior cruciate ligament cause?
large gapping of posterior side of the joint
how do most fibers resist knee flexion?
- excessive posterior translation of tibia
- excessive anterior translation of femur
what kinds of risk factors increase risk of anterior collateral ligament (ACL) rupture?
- environmental factors
- anatomical factors
- biomechanical factors
- physiological factors
what environmental factors increase the risk for anterior collateral ligament (ACL) rupture?
- improper footwear
- bracing
- playing conditions
- weather/climate
what anatomical factors increase the risk for anterior collateral ligament (ACL) rupture?
- bone & joint alignment involving Q-angle & foot pronation
- body mass index
- femoral intercondylar notch width
- posterior-inferior directed slope of lateral tibial plateau
what biomechanical factors increase the risk for anterior collateral ligament (ACL) rupture?
- muscular strength, stiffness, & fatigue
- hamstring-quadriceps strength ratio
- neuromuscular control of the body during landing & cutting maneuvers
- cross sectional area strength of ACL
what physiological factors increase the risk for anterior collateral ligament (ACL) rupture?
- physical maturation
- hormonal fluctuations
- limb dominance
- proprioception or kinesthesis
- overall joint laxity
- genetic predisposition
what muscles are involved in for lower extremity muscular strength, stiffness, & fatigue?
- hamstring muscles
- gluteus maximus
- hip abductor muscles
- external rotators
functions of menisci
- shock absorption
- stabilization of tibiofemoral joint
- joint lubrification
- proprioception
- helps to guide knee motions
describe the lateral meniscus
- almost O-shaped with a small opening
- covers around 60% of lateral tibial plateau
- loosely attached
describe the medial meniscus
- C-shaped with greater opening
- covers about 50% of medial tibial plateau
- firmly attached
- medial collateral ligament has fibers attaching to medial meniscus
what are the movements that can occur at the knee?
- flexion/extension
- internal/external rotation
structural/functional causes of lateral tracking
- body dysplasia/ other anomaly
- excessive laxity in periarticular connective tissue
- excessive stiffness in periarticular connective tissue & muscle
- extremes of bony/joint alignment
- muscle weakness
specific examples of body dysplasia/other anomaly
- dysplastic lateral facet of trochlear groove of femur
- “high” patella
specific examples of excessive laxity in periarticular connective tissue
- laxity of medial patellar retinacular fibers (medial patellofemoral ligament)
- laxity of attrition of medial collateral ligament (MCL)
- laxity & reduced height of medial longitudinal arch of foot (overpronation of subtalar joint)
specific examples of excessive stiffness in periarticular connective tissue & muscle
- increased tightness in lateral patellar retinacular fibers/iliotibial band
- increased tightness of internal rotator/adductor muscles of the hip
specific examples of extreme bony/joint alignment
- coxa verus
- excessive anteversion of femur
- external tibial torsion
- large Q-angle
- excessive genu valgum
specific examples of muscle weakness
weakness or poor control over:
- hip external rotator/abductor muscles
- vastus medialis (oblique fibers)
- tibialis posterior muscle (related to foot overpronation)
