Download - Bio Mechanics of the Knee
![Page 1: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/1.jpg)
Biomechanics Biomechanics of of
the Kneethe Knee
![Page 2: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/2.jpg)
Bony StructuresBony Structures
• Complex joint consists of– Femur– Tibia– Fibula– Patella
• Hinge joint w/ a rotational component
![Page 3: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/3.jpg)
Joints of the Knee
• Tibiofermoral joint
– Dual condyloid
articulations
between the medial
and lateral condyles
of the tibia and the
femur
![Page 4: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/4.jpg)
• Patellofemoral joint
– Articulation between the patella and the femur
– The patella improves the mechanical advantage of the knee extensors by as much as 50%
Joints of the knee
![Page 5: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/5.jpg)
• Collateral ligaments - cross the
medial and lateral aspects of the
knee
– Medial Collateral ligament
– Lateral Collateral ligament
Ligamentous Support
![Page 6: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/6.jpg)
![Page 7: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/7.jpg)
lateral (fibular)
medial (tibial)
Collateral Ligaments
Prevents abduction and adduction movement of the knee
![Page 8: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/8.jpg)
Ligamentous Support
• Cruciate ligaments - cross each
other in connecting the anterior
and posterior aspects of the knee
– Anterior cruciate ligament
– Posterior cruciate ligament
![Page 9: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/9.jpg)
![Page 10: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/10.jpg)
Anterior Cruciate Ligament
• Prevent anterior luxation
• Primary static restraint to anterior
displacement
• Limit tibia rotation upon femur
– Esp, internal rotation
• Limit valgus and varus stress upon
knee
![Page 11: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/11.jpg)
Anterior Cruciate (ACL)
Anterior Cruciate Ligament
![Page 12: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/12.jpg)
• Knee stabilizer
• Primary restraint to posterior
displacement 90%
• Limit internal rotation of tibia upon
femur during weight bearing
• Resist hyperextension
Posterior Cruciate Ligament
![Page 13: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/13.jpg)
Posterior Crucuate (PCL)
shorter and stronger thanACL
Posterior Cruciate Ligament
![Page 14: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/14.jpg)
![Page 15: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/15.jpg)
FEMUR
TIBIA
PATELLA
The ACL prevents the femur from sliding posteriorly on the tibia or the tibia from sliding anteriorly on the femur
The PCL prevents the femur from sliding anteriorly on the tibia or the tibia from sliding posteriorly on the femur
![Page 16: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/16.jpg)
![Page 17: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/17.jpg)
![Page 18: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/18.jpg)
Additional Ligamentous
Support
•iliotibial bandthick, strong band of tissue connecting tensor fascia latae to femur and tibia
![Page 19: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/19.jpg)
Menisci
• Cartilaginous discs located between
the tibial and femoral condyles
• The menisci distribute the load at
the knee over a large surface area
and also help absorb shock
![Page 20: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/20.jpg)
• The lateral meniscus is smaller and
more mobile than the medial
meniscus
• The inner portion of the menisci are
avascular
Menisci
![Page 21: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/21.jpg)
Menisci Function• Increases stability by deepening tibial
plateaus
• Decreases friction by 20%
• Increases contact area by 70%
• Absorbs shock
• Distribute pressure between femur and tibia in weight bearing
• Balance intra-articular pressure of muscle action
![Page 22: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/22.jpg)
![Page 23: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/23.jpg)
![Page 24: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/24.jpg)
![Page 25: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/25.jpg)
Menisci Function• Increases stability by deepening
tibial plateaus• Decreases friction by 20%• Increases contact area by 70%• Absorbs shock• Distribute pressure between femur
and tibia in weight bearing• Balance intra-articular pressure of
muscle action
![Page 26: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/26.jpg)
![Page 27: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/27.jpg)
Bursae & Fat Pad of the Knee
![Page 28: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/28.jpg)
• Stability is due primarily to
ligaments, joint capsule and
muscles surrounding the joint
• Designed for stability w/ weight
bearing and mobility in locomotion
Knee Articulations
![Page 29: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/29.jpg)
Knee Articulations
• Tibiofemoral Joint– Modified hinge
joint
– 2-3 degrees of freedom
– Articulating surfaced are not congruent
![Page 30: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/30.jpg)
Knee Articulations
• Proximal
Tibiofibular Joint
– Syndesmosis joint
![Page 31: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/31.jpg)
Knee Articulations
• Patellofemoral Joint– Medial and lateral facets of the femoral
condyles articulate with patella
![Page 32: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/32.jpg)
![Page 33: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/33.jpg)
Knee Movements
![Page 34: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/34.jpg)
Axis of Rotation
![Page 35: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/35.jpg)
Axis of Rotation
![Page 36: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/36.jpg)
Knee Goniometry
• Flexion– 0-130-140 degrees
• Extension– 0 degree
• Screw Home Mechanism
![Page 37: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/37.jpg)
Screw Home Mechanism• Locking mechanism as the knee nears its
final extension– Automatic rotation of the tibia externally
(approx. 10 degrees) during the last 20 degrees of knee extension
• Forms a close-packed position for the knee joint
• Femoral condyles are a different size– Causes internal rotation when the knee
is flexed and external rotation when the knee is extended
![Page 38: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/38.jpg)
![Page 39: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/39.jpg)
Knee Rotation
FlexionExternalRotation
InternalRotation
Extension
![Page 40: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/40.jpg)
![Page 41: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/41.jpg)
![Page 42: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/42.jpg)
Patella migrates posteriorly from extension to flexion
30 60 90
Patellar Translation
![Page 43: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/43.jpg)
• Normal length of patellar tendon = patellar height: 1:1 ratio
Patellar Contact Areas
![Page 44: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/44.jpg)
1200
Patellar Contact Areas
![Page 45: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/45.jpg)
Mechanical Function of Patella
(1) Increases angle of pull of quads on tibia, improves the ratio of motive: resistive torque by 50%
(2) Centralizes divergent tension of quads into a single line of action
(3) Some protection of anterior aspect of knee
without patella
with patella
![Page 46: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/46.jpg)
Mechanical Function of Patella
• Patella contributes to quadriceps moment arm– 13% at 90o
– 31% at 0o
• No angle without patella & therefore no compressive resultant force
![Page 47: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/47.jpg)
• Stabilizes patella in trochlea groove
• Patella assures “some” compression in full extension
• Patella not in femoral sulcus however
Sagittal Plane PF Joint Sagittal Plane PF Joint Mechanics: Mechanics: PF Compressive PF Compressive Force FunctionForce Function
![Page 48: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/48.jpg)
Patellofemoral Compressive Force
Mechanics
• PFC force with flexion– 0.5 x BW gait– 3.4 x BW stairs– 8.8 x BW squatting
![Page 49: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/49.jpg)
Q-Angle
• The Q-angle is the angle
formed by
– A line from the anterior
superior spine of the ilium
to the middle of the patella
– A line from the middle of
the patella to the tibial
tuberosity
![Page 50: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/50.jpg)
Q-angle
• Knee in extension– Normal – males 13 degrees– Normal - females – 18 degrees
• Knee in 90 degrees flexion– Both genders – 8 degrees
![Page 51: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/51.jpg)
Atypical Q-anglesbowleggedness
knock-knees
Genu Recurvatum
knee hyperextension
![Page 52: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/52.jpg)
Posture & WB Forces
• The mechanical axis of TF joint is the weight bearing line from the center of femoral head to superior talus center
• Allows WB in stance of the medial = lateral Tibiofemoral compartments
![Page 53: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/53.jpg)
• Increase in valgus results: – Compression
overload to the lateral Tibiofemoral compartment
– Distraction overload to medial Tibiofemoral compartment
Posture & WB Forces
![Page 54: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/54.jpg)
• Decrease in valgus results – Compression
overload to the medial Tibiofemoral compartment
– Distraction overload to lateral Tibiofemoral compartment
Posture & WB Forces
![Page 55: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/55.jpg)
Joint Mechanics
• Resultant force has a tendency to laterally translate the patella
![Page 56: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/56.jpg)
• Laterally displace tibial tubercle– external tibial rotation– external tibial torsion
• Medially displace patella– internal femoral rotation– femoral anteversion
• Laterally displace ASIS (ASIS)– females
Joint Mechanics
![Page 57: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/57.jpg)
Tibial Torsion
• Tibial torsion– An angle that
measures less than 15 degrees is an indication of tibial torsion
– I nward twisting of the tibia (and is the most
common cause of intoeing
![Page 58: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/58.jpg)
Movements of the knee
• Flexion– hamstrings– assisted by:
• gracilis• sartorius• popliteus• gastrocnemius
![Page 59: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/59.jpg)
![Page 60: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/60.jpg)
Muscle Pull
![Page 61: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/61.jpg)
Gracilis
Sartorious
![Page 62: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/62.jpg)
Popliteus
![Page 63: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/63.jpg)
Gastrocnemius
![Page 64: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/64.jpg)
Movements of the knee
• Extension– quadriceps:
• rectus femoris• vastus lateralis• vastus medialis• vastus intermedius
![Page 65: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/65.jpg)
Rectus femoris
![Page 66: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/66.jpg)
Vastus lateralis
Vastus intermediate
Vastus medialis
![Page 67: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/67.jpg)
Muscle Pull
![Page 68: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/68.jpg)
Loads on Knee
• Forces at tibiofemoral Joint
– Shear stress is greater during open
kinetic chain exercises such as knee
extensions and knee flexions
– Compressive stress is greater during
closed kinetic chain exercises such as
squats and weight bearing exercises
![Page 69: Bio Mechanics of the Knee](https://reader031.vdocument.in/reader031/viewer/2022012400/5468d849b4af9f0e518b48eb/html5/thumbnails/69.jpg)
Loads on Knee
• Forces at Patellofemoral Joint
– With a squat, reaction force is 7.6
times BW on this joint
•Beneficial to rehab of cruciate
ligament or patellofemoral surgery