1. The Knee Complex

2. The Knee Complex General Structure & Function
Structure & Function of Specific Joints
Muscular Considerations

3. General Structure

5. Joints of the Knee Complex

6. General Function
Provides very mobile link in an otherwise stable lower extremity
Transmits loads from tibia/fibula to femur

9. Knee Complex Movements

10. Transverse plane
Medial and lateral
rotation
Sagittal plane
Flexion, extension

11. Knee Complex Movements
Frontal plane
Varus, valgus
Anteroposterior translation
Mediolateral translation

12. The Knee Complex General Structure & Function
Structure & Function of Specific Joints
Muscular Considerations

13. Structure & Function of Specific Joints
Tibiofibular Joint
Patellofemoral Joint
Tibiofemoral Joint

14. Tibiofibular Joint: Bony Structure
Amphiarthrodial membranous syndesmosis joint

15. Structure & Function of Specific Joints
Tibiofibular Joint
Patellofemoral Joint
Tibiofemoral Joint

16. Purpose of Patella Increase leverage of QF
Protect joint during knee flexion
↓ pressure and distribute forces on femur
Prevent Fcompression on PT in resisted knee flexion
Disadvantage:  ANT shear of QF
Increase leverage of QF
Protect joint during knee flexion
↓ pressure and distribute forces on femur
Prevent Fcompression on PT with resisted knee flexion as in deep knee bends

17. Patella Structure
Medial facet
Lateral facet
Odd facet (30%) M L

18. PF Articular Surfaces Largest sesamoid bone Least congruent joint
Articular cartilage
Vertical ridge
Facets M L
Largest sesamoid bone
Least congruent joint in body
Posterior surface covered with articular cartilage
Vertical ridge on posterior, typically in center but can be situated more medially
30% of patellae have a second vertical ridge toward medial border, creating the odd facet on the extreme medial edge
Angle of femoral sulcus (angle formed by medial & lateral facets of femur) averages 138° but varies widely (116° -151°)

19. PF Articular Surfaces Largest sesamoid bone Least congruent joint
Articular cartilage
Vertical ridge
Facets
Angle of femoral sulcus
Largest sesamoid bone
Least congruent joint in body
Posterior surface covered with articular cartilage
Vertical ridge on posterior, typically in center but can be situated more medially
30% of patellae have a second vertical ridge toward medial border, creating the odd facet on the extreme medial edge
Angle of femoral sulcus (angle formed by medial & lateral facets of femur) averages 138° but varies widely (116° -151°)

20. Patellar Motion INF & SUP Sliding Patellar tilt 11 MT as KN FL Med
Lat
Sliding during knee flexion – enters sulcus at 20° of knee flexion
Patellar tilt
rotation about vertical axis to medial side of 11°
occurs as knee flexion occurs

21. Patellar Motion Lateral rotation Medial rotation ACC MR of femur
6 through KN FL
Medial rotation
ACC LR of femur
Lateral rotation of patella (around AP axis)
with medial rotation of femur on tibia (top of patella goes with femur (7° - most by 60 ° of knee flexion)
Medial rotation of patella (around AP axis)
with lateral rotation of femur on tibia
Failure to slide, tilt, or rotate will lead to restriction of knee joint ROM, instability of PF joint, or pain due to erosion of PF surfaces

22. Patellalectomy ↓ MA of QF (↓ strength 49%)  Q tendon friction
 compressive stress on groove by Q tendon
Most evident in closed chain EXT
ECC QF in CC
Coupled w/ & assisted by hip & ankle movement
QF not needed in erect posture of CC

23. Extension
Little effect overall

24. Slight Flexion
Noticeable weakness

25. Extreme Flexion
Noticeable weakness

26. From 0° to 60° of Knee Flexion

27. 0-60
Contact area 
 MA of QF;  60
 ANT shear of QF
0-60
Facet contact at 20

28. From 60° to 140° of Knee Flexion

29. 60-140
 contact area
 MA of QF
No leverage in full FL

30. Overall
Medial facet most contact
Odd facet least contact

31. During Full Extension Full EXT  MA of QF  QF length
Patella very unstable

32. PF JRF Amount of knee FL Strength of QF contraction
Collinear pull of patella tendon (inferior) and quadriceps tendon (superior) results in little or no contact with femur in full extension
Justification for use of straight-leg raises to improve quad strength without creating or exacerbating PF problems
With knee flexion, the pull of these tendons create a compressive force on patella into femur (Fig ) (occurs with active or passive mechanism due to elasticity of tendon)
FQ and FP are generally not equal – depend on knee joint angle (Fig. 6.2)
Creates JRF (magnitude of JRF depends on magnitude of active and passive pulls, and degree of knee flexion)
JRF during gait at foot contact (10° -15° of knee flexion) is 50% of body weight
In running, JRF may increase to 3.3X (60° of knee flexion & more vigorous muscle contraction)
7.8X BW (130° of knee flexion with strong muscle contraction) in deep knee bends
Lack of congruency at this joint results in this force distribution occurring over smaller area – more stress/pressure
Medial facet bears the brunt of this, but there are mechanisms to minimize this
Lowest at knee flexion < 30 degrees

34. PF Compressive Forces Descending stairs 4000 N Max isometric extension
Kicking
6800 N
Parallel squat
14,900 N (7-8X BW)
Isokinetic knee extension
8300 N
Rising from chair
3800 N
Running/jogging
5000 N (3-4X BW)
Ascending stairs
1400 N
Walking
N ( X BW)
Cycling
880 N

35. Compensatory Mechanisms for Compressive Force Distribution
Contact area  with knee flexion
Medial facet contact from 30-70
Thickest hyaline cartilage in body

37. Compensatory Mechanisms for Compressive Force Distribution
Contact area  with knee flexion
Medial facet contact from 30-70
Thickest hyaline cartilage in body
Largest QF MA 30-70
QF torque as MA decreases
QF tendon contacts condyles 70-90

38. Normal Patella Tracking
Maintains maximum congruence
Passive restraints
Active restraints

39. Abnormal Patella Tracking
↓ congruence
Stretches capsule & retinacula
↓ contact area
Lateral
Medial

40. Causes of Abnormal Tracking
Skeletal abnormalities
Strength imbalance in QF
Strength imbalance in fibrous tissues
Compensatory movements in knee due to abnormal foot movement

41. Causes of Abnormal Tracking
Skeletal abnormalities
Strength imbalance in QF
Strength imbalance in fibrous tissues
Compensatory movements in knee due to abnormal foot movement

42. Skeletal Abnormalities: Q-angle

43. Skeletal Abnormalities: Genu Varum & Genu Valgum
Q angle  w/ age
Varum common in very young children
Valgum seen in growing children
Menisectomy effects

44. Skeletal Abnormalities: Patella Alta & Patella Baja
Index of Insall & Salviti
LT/LP
Normal = 1.0
Patella alta = 0.8
Patella baja = 1.2
Women  ratio

45. Skeletal Abnormalities: Patella Surface Lateral Border
Appositional forces ↓ in full extension
Prominence of lateral border prevents lateral displacement
Underdevelopment common in children as growing

46. Skeletal Abnormalities: Femoral & Tibial Torsion
Lateral tracking

47. Causes of Abnormal Tracking
Skeletal abnormalities
Strength imbalance in QF
Strength imbalance in fibrous tissues
Compensatory movements in knee due to abnormal foot movement

48. QF Strength Imbalance

49. Causes of Abnormal Tracking
Skeletal abnormalities
Strength imbalance in QF
Strength imbalance in fibrous tissues
Compensatory movements in knee due to abnormal foot movement

50. Fibrous Tissue Strength ImbalanceIT

51. Causes of Abnormal Tracking
Skeletal abnormalities
Strength imbalance in QF
Strength imbalance in fibrous tissues
Compensatory movements in knee due to abnormal foot movement

52. Compensatory Movement
Pronation of foot accompanied by medial rotation of tibia  medial rotation & medial translation of patella
Pronation coupled w/ forceful quadriceps femoris leads to anterior tilt
EX: jumping, landing, running

53. Summary