Knee Complex Biomechanics & Kinesiology Flashcards
Sagittal plain TF biomechanics
9 degree posterior tibial slope
Run out of room laterally during sliding
Starts transverse plane motion. One goes up the slope one goes down, creates frontal plane angulation
TF Joint sagittal plane osteokinematics
Flexion 130-140 with hip flexion
Flexion 120 with hip extension
Extension 5-10 degrees
TF requirements for specific activity
Level surface gait 60-68 degrees flexion Stairs 80 degrees up 90 degrees down Sit to stand transfers 90 degrees Tying a shoe 106 degrees Full squat to floor 150-160 degrees
TF OKC Extension sagittal plane arthrokinematics
Convex femoral condyles
Concave tibial plateau
Roll and slide in same direction
Menisci translate anterior due to meniscopatellar ligaments
TF OKC Flexion sagittal plane arthrokinematics
Convex femoral condyles
Concave tibial plateau
Roll and slide in same direction
Menisci translate posterior due to semimembranosus and popliteus
Function of the menisci
Increase tibial plateau radius of curvature
Reduces TF friction
Attenuates TF compression loads
TF CKC Flexion Sagittal Plane Arthrokinematics
Convex on concave
Opposite Gliding from rolling
Initially, predominantly posterior roll followed by anterior slide
TF CKC Flexion Early ROM
By 15 degrees flexion in the medial compartment posterior roll begins to have anterior slide
By 25 degrees flexion the lateral compartment roll begins to have anterior slide
TF CKC Flexion Mid ROM
Approximately equal magnitude of posterior roll and anterior slide in both compartments
TF CKC Flexion End ROM
Essentially all anterior femoral slide in both compartments
TF CKC Flexion ACL control
Angle of ACL inclination greatest at full extension
Anterior directed component force will eventually restrain posterior femoral roll
As TF flexion increases, angle of inclination decreases
Hyperextension Impact on ACL
End ROM extension brings the midsubstance of the ACL in contact with the femoral intercondylar shelf
Notch of grant acts as a fulcrum to tension load to the ACL
ACL Orientation
Anteromedial to posterolateral
Anteromedial band taut in greater degrees of flexion
Posterolateral Band taut in greater degrees of extension
Greatest excursion of tibia anteriorly at….
30 degrees of flexion when neither band of ACL is particularly taut
TF CKC Flexion PCL Control
Angle of inclination of PCL greatest at full flexion
Posterior directed force will restrain anterior femoral roll
As tibiofemoral extension increases, PCL angle of inclination decreases
TF Joint Transverse Plane Osteokinematics
TF Rotation at 90 degrees of flexion
-40 degrees lateral
-30 degrees medial
Axis of rotation is longitudinal axis running medial to medial tibial intercondylar tubercle
Results in greater excursion laterally during rotation
Medial rotation of knee checked by
Cruciate ligaments
Lateral rotation of knee checked by
Collateral ligaments
Transverse Plane Femoral Condyle Asymmetry
LFC lies in sagittal plane: acts as buttress for patella
MFC lies oblique to sagittal plane
Screw Home Mechanism
Automatic ER of tibia with terminal 20-30 degrees of knee extension
TF Joint Frontal Plane Posture
Anatomic or longitudinal axis of the tibiofemoral joint is 5-10 degrees of valgus
Femoral longitudinal is oblique due to proximal femoral angle of inclination
Mechanical Axis of the TF Joint
Weight bearing line from the center of the femoral head to superior talus center
Allows WB in stance of the medial & lateral TF Compartments
Increase in valgus results in…
Compression overload to the lateral compartment
Distraction overload to the medial TF Compartment
Increase in varus results in…
Compression overload to the medial TF compartment
Distraction overload to the lateral TF compartment
Etiology of coupled motion Frontal Plane TF
In ER, Lateral Femoral Condyle climbs up tibial slope
Lengthens the lateral compartment
Medial Femoral Condyle falls down tibial slope
Shortens medial compartment
Frontal Plane TF Osteokinematics
Slight valgus with IR
Slight varus with ER
Patellar Function
Contributes to quadriceps moment arm
13% at 90 degrees flexion
31% at 0 degrees flexion
No angle without patella therefore no compressive resultant
PF compressive force function
Stabilizes patella in trochlea groove
Patella assures some compression in full extension
Patella not in femoral sulcus
PFC force ___ with ____ flexion
Increases; Increased
Patellar contact areas
Superior at 90
Middle at 45
Inferior at 20
Medial and Lateral at 120
Normal length of patellar tendon
Equal to patellar height
ITB impact on patellofemoral mechanics
The fascial slip from the ITB to the patella will add a force with a tendency to laterally translate the patella
Quadriceps angle
Resultant force has a tendency to laterally translate the patella
13 in males
18 in females
Increased Q angle
Laterally displaced tibial tuburcle -External tibial rotation and torsion Medially displaced patella -Internal femoral rotation -Femoral anteversion Laterally displaced ASIS
When do we sublux
At the greatest Q angle
Least PF compressive forces
Greatest Quad force
Least patellar contact with femoral trochlea
Full extension or hyperextension
