1. Biomechanical Considerations for Rehabilitation of the Knee James J. Irrgang, MS, PT, ATC Department of Physical Therapy University of Pittsburgh and Centers for Rehab Services Pittsburgh PA

2. Bony Architecture of the Knee Femur Femur Tibia Tibia Patella Patella

3. Tibio-Femoral Joint Medial Compartment

4. Tibio-Femoral Joint Lateral Compartment

5. Patello-Femoral Joint

6. Restraints to Patellar Motion Bony architecture Bony architecture Passive restraints Passive restraints Active restraints Active restraints

7. Restraints to Patellar Motion Medial retinaculum Medial retinaculum Medial P-F ligament Medial P-F ligament Medial menisco-patellar ligament Medial menisco-patellar ligament Medial Restraints

8. Restraints to Patellar Motion ITB ITB Lateral P-F ligament Lateral P-F ligament Lateral patello-tibial ligament Lateral patello-tibial ligament Lateral Restraints

9. Restraints to Patellar Motion Vastus lateralis Vastus lateralis Vastus medialis Vastus medialis Vastus intermedius Vastus intermedius Rectus femoris Rectus femoris Active Restraints

10. Patellofemoral Motion Flexion - patella glides inferiorly Flexion - patella glides inferiorly Extension - patella glides superiorly Extension - patella glides superiorly

11. Patello-Femoral Contact

12. Patello-Femoral Contact Area

13. Patellofemoral Joint Reaction Force Angle of knee flexion Angle of knee flexion Quadriceps force Quadriceps force Function of:

14. Quadriceps Force Flexion moment arm of T-F joint Flexion moment arm of T-F joint Extension moment arm of P-F joint Extension moment arm of P-F joint Dependent on:

15. Open Chain Knee Extension Increased flexion moment arm Increased flexion moment arm Increased quadriceps force Increased quadriceps force PFJR force peaks at 35 0 PFJR force peaks at 35 0 Decreased contact area results in increasing contact stress from 90 to 20 0 of flexion Decreased contact area results in increasing contact stress from 90 to 20 0 of flexion Increasing Extension

16. Closed Chain Knee Extension Increased flexion moment arm Increased flexion moment arm Increased quadriceps force Increased quadriceps force Increased PFJR Increased PFJR Increased contact area partially off-sets increasing PFJR to minimize increase in contact stress Increased contact area partially off-sets increasing PFJR to minimize increase in contact stress Increasing Flexion

17. Open vs. Closed Chain Exercise PFJR & contact stress greater with OKC from 0 to 45 0 PFJR & contact stress greater with OKC from 0 to 45 0 PFJR & contact stress greater with CKC from 45 to 90 0 PFJR & contact stress greater with CKC from 45 to 90 0

18. Patellofemoral Joint Reaction Force Walking -.5 times body weight Walking -.5 times body weight Stairs - 3 to 4 times body weight Stairs - 3 to 4 times body weight Squatting - 7 to 8 times body weight Squatting - 7 to 8 times body weight During Functional Activities

19. EMG Activity of Quadriceps EMG relatively low & increases with increasing angle of knee flexion EMG relatively low & increases with increasing angle of knee flexion Closed Chain:

20. EMG Activity of Quadriceps EMG activity increases with decreasing angle of knee flexion EMG activity increases with decreasing angle of knee flexion Open Chain:

21. Ligamentous Restraints of Knee Collateral ligaments Collateral ligaments Cruciate ligaments Cruciate ligaments Capsular ligaments Capsular ligaments

22. Ligamentous Restraints of Knee Medial Collateral Ligament

23. Ligamentous Restraints of Knee Lateral Collateral Ligament

24. Ligamentous Restraints of Knee Cruciate Ligaments

25. 4 - Bar Linkage System

26. Arthrokinematics of Knee ACL slides femoral condyles anteriorly as femur rolls posteriorly ACL slides femoral condyles anteriorly as femur rolls posteriorly Flexion

27. Arthrokinematics of Knee PCL pulls femoral condyles posteriorly as femur rolls anteriorly PCL pulls femoral condyles posteriorly as femur rolls anteriorly Extension

28. Cruciate Ligament Injury Results in Abnormal Kinematics

29. ACL Strain Open Chain Knee Extension

30. Closed Chain Exercise Joint compression Joint compression Hamstring co- contraction Hamstring co- contraction Angle of force application Angle of force application ACL Strain Reduced

31. ACL Strain In-vivo Studies Active Squat Squat with Sport Cord

32. Meniscii Absorb shock Absorb shock Distribute weightbearing Distribute weightbearing Provide stability Provide stability Aid in lubrication Aid in lubrication Function

33. Meniscii Load Bearing Function

34. Meniscii Glide anteriorly with extension Glide anteriorly with extension Glide posteriorly with flexion Glide posteriorly with flexion Motion

35. Mensicii Microvasculature

36. Restraints to Rotation MCL MCL LCL LCL External Rotation

37. Restraints to Rotation ACL ACL PCL PCL Meniscofemoral ligaments Meniscofemoral ligaments Internal Rotation

38. Dynamic Motion Control