Biomechanics introductory lecture for undergraduate year 1.

1. Biomechanics of
Tibiofemoral Joint
Lecture 2
• Tibiofemoral Osteokinematics
• Tibiofemoral Arthokinematics
• Automatic Locking/ Screw Home Phenomenon

2. Contents
1. Tibiofemoral Arthokinematics
2. Tibiofemoral Osteokinematics
3. Automatic Locking/ screw home phenomenon
2

3. Two degree freedom of motion
• Flexion extension- coronal axis/ migrating medial
lateral axis (the evolute)
• Internal/ external rotation- vertical axis
• + Passive frontal plane motion
Osteokinematics of knee joint

4. Osteokinematics
Flexion Extension
In normal = 130o- 150o
Hyperextension= 5o- 10o
In squatting = 160o
Gait = 60o- 70o
Ascending stairs = 80o
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5. Osteokinematics- Flx/ Ext
5 Neumann, 2010

6. “Evolute”
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Migrating axis
Neumann, 2010

7. Osteokinematics
(Axial) Rotations Valgus and varus
At 90o flexion
Medial Rotation= 0-15o
Lateral Rotation= 0-30o
In Extension = 6-7o (only
passive)
With 20o knee flexion = 13o
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 Axial rotation increases with knee flexion.
 Total rotation in 90o flexion = 40- 45o
 External rotation to internal rotation= 2:1
 Naming the rotation- based on orientation of tibial
tuberosity

8. Osteokinematics
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 Naming the rotation- based on orientation of tibial
tuberosity with respect to distal anterior femur
Neumann, 2010

9. Osteokinematics
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Variability:
 Age
 Gender

10. Arthrokinematics: Knee Joint
Norkin and Levengie

11. Arthrokinematics
11
Norkin and Levengie

12. Arthrokinematics:
Tibia on femoral extension
12 Neumann, 2010

13. Arthrokinematics:
Femur on Tibia Extension
13 Neumann, 2010

14. Arthrokinematics
Role of cruciate ligaments
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15. 15 Neumann, 2010

16. • Locking full extension requires 10 degrees of
external rotation
• Increases joint congruency and stability
Locking and Unlocking Mechanism

17. 17 Neumann, 2010

18. Automatic or terminal rotation
 Coupled motion of lateral rotation and
extension of knee
 Non-voluntary (Automatic)
 Locks the knee joint
 Keeps knee to remain in full extension in
standing
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19. Non weight bearing
A-P diameter of Lat F condyle < Med F condyle
During last 30° of extension, glide and roll in
Lateral condyle finishes but not in medial
condyle
Lateral condyle serves as an axis for the medial
condyle to rotate backwards i.e. Lateral rotation
of tibia on femur occurs
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20. Non weight bearing
 This is locking of knee or Screw Home
Phenomenon
 Locking makes all ligaments taut
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21. Non Weight Bearing: Unlocking
 Knee flexes only if unlocked
 It happens with medial rotation of tibia on
femur
 Unlocking is brought about by Popliteus
muscle
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22. Weight bearing
 Locking: femur rotates medially on relatively
fixed tibia during last 30° of extension
 Unlocking: lateral rotation of femur on tibia
before flexion proceeds
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23. Factors guiding Screw home Rotation
 Shape of Medial femoral condyle
 Tension in ACL
 Lateral Pull of the Quadriceps
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24. Summary
 Osteokinematics
 Arthrokinematics
 Screw home phenomenon
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25. References:
 Norkin C, Levengie P. Joint structure and
function. 4th Edition
 Neumann DA. Kinesology of musculoskeletal
system, Foundation for Physical Rehabilitation,
2nd Edition
 Kapandji IA. The Physiology of Joints. Volume 2,
Lower Limb. 5th Edition
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