1. BIOMECHANICS OF KNEE
U.RADHAKRISHNAN.M.P.T

2. INTRODUCTION
Knee Joint produces Functional shortening and Lengthening of extremity
Knee complex plays a major role in supporting the body in Dynamic and Static situation
The Knee complex is composed of
TIBIOFEMORAL JOINT
PATELLOFEMORAL JOINT

3. KNEE COMPLEX

4. TIBIOFEMORAL JOINT ARTICULATION:
ON DISTAL FEMUR Convex,Asymmetric,Medial and Lateral condyle
ON PROXIMAL TIBIA Concave,Asymmetric,Medial and Lateral Plateau
The FEMORAL CONDYLES are twice as large as length of TIBIAL CONDYLES

5. MENISCI Fibrocartilaginous Joint Disc
Medial and Lateral Menisci---asymmetric
The two ends are called horns
Coronary ligament attaches the Menisci to Tibial plateau
Transverse ligament joins the two Menisci
Medial Menisci is more fixed and attached to capsule and Medial collateral ligament. They are less mobile and prone to injury

6. MENISCUS

7. FUNCTIONS OF MENISCI Stability & Mobility Function STABILITY:
Deepens articular surface
Keeps the joint surface tight
Distribute the load
MOBILITY:
Reduces friction

8. JOINT CAPSULE & BURSAE
Joint capsule encloses Tibiofemoral and Patellofemoral Joint.
It is large,lax,with many folds
The deep folds of capsule forms the Bursae
Suprapatellar Bursae
Prepatellar Bursae
Infrapatellar Bursae
Subpopleteal Bursae
Gastrocnemius Bursae

9. BURSAE

10. LIGAMENTS INTRACAPSULAR LIGAMENT
ANTERIOR CRUCIATE LIGAMENT: Extends superiorly and posteriorly attached to posterior part of inner aspect of Lateral condyle of Femur.It is more prone for injury eg. Foot ball players
POSTERIOR CRUCIATE LIGAMENT: Extends superiorly and anteriorly to attach to anterior portion of inner aspect of Medial femoral condyle

11. LIGAMENTS

12. LIGAMENTS

13. LIGAMENTS MEDIAL COLLATERAL LIGAMENT:(TIBIAL)
Extends from medial Femoral condyle to medial part of proximal Tibia,attaches with medial meniscus
LATERALCOLLATERALLIGAMENT:(FIBULAR)
Extends from Lateral Femoral condyle to head of Fibula

14. LIGAMENTS

15. STABILITY OF KNEE STABILITY LIGAMENTS MUSCLES MEDIAL STABILITY
MEDIAL COLLATERAL
SEMIMEMBRANOSUS
LATERAL STABILITY
LATERAL COLLATERAL
POPLITEUS.IT BAND
ANTERIOR STABILITY
ANTERIOR CRUCIATE
QUADRICEPS,
PATELLA
POSTERIORSTABILITY
POSTERIOR CRUCIATE
BICEPS FEMORIS,POPLITEUS
ANTEROMEDIAL
MEDIAL COLLATERAL,ANTERIOR CRUCIATE
QUADRICEPS
ANTERIOLATERAL
LATERAL COLLATERAL,POSTERIOR CRUCIATE
POSTERIOR MEDIAL
OBLIQUE POPLITEAL LIGAMENT
POSTERIOR LATERAL
ARCUATE POPLITEAL
POPLITEUS

16. ANATOMIC AXIS
A Line runs along the shaft of the Femur and shaft of Tibia they form angle of 170 to 175 degree
When the angle is less than 165 degree an abnormal condition called GENU VALGUM,
The medial aspect of knee is subjected to distraction force
When the angle is more than 180 degree an abnormal condition called GENU VARUM
The medial aspect of knee is subjected to Increase compression loading

17. MOVEMENTS FLEXION- EXTENSION Saggital plane,Mediolateral axis ROTATION
Transverse plane,vertical axis
Flexion active range is 120 degree restricted by contact of posterior muscle,active insufficiancy
passive range is 130 degree

18. MOVEMENTS
During complete Extension, the Tibial tubercle locks in to intercondylar fossa of Femur, it is the closed packed position.
ROTATION:
It is not possible when knee in full Extension as ligaments are taught
When Knee in 90 degree Flexion---- Rotation is possible, Lateral rotation is 40 degree and Medial rotation is 30 degree
ABDUCTION can be done passively

19. ARTHROKINEMATICS FLEXION AND EXTENSION:
During Flexion from full Extension Femoral condyles roll in an posterior direction with sliding anteriorly.In First part of Flexion consist of Rolling and spinning
During Extension from full Flexion Femoral condyles roll in an anterior direction with sliding posteriorly.In last few degrees of Extension Femoral condyles Roll and Spin on Tibia
Pure Rolling will move condyles out

20. LOCKING AND UNLOCKING
The spin of Femur in last few degree of Extension causes a Medial rotation of Femur on Tibia will keep joint in closed packed position, so Femoral rotation is called LOCKING or SCREW HOME MECHANISM.The Knee is Unlocked by Lateral rotation of Femur
In open Kinematic chain Tibia laterally rotates on Femur during last few degrees of Extension to produce LOCKING.Unlocking by Medial rotation.

21. MUSCLES EXTENSORS QUADRICEPS
The efficiency of Quadriceps depends on PATELLA,it increases the moment arm
Supports the body weight
Resist the force of gravity

22. MUSCLES FLEXORS HAMSTRINGS
Work more effectively in Knee if they are lengthened over a Flexed hip

23. PROBLEMS OF TIBIOFEMORAL JOINT
MEDIAL MENISCUS INJURY:
More common,it is fixed, attached to capsule
ANTERIOR CRUCIATE LIGAMENT INJURY:
More common in foot ball players
GENU VALGUM/GENU VARUM
PREPATELLAR BURSITIS:
Inflammation of Prepatellar bursae,common in workers who kneel and work

24. MENISCUS INJURY

25. GENU VALGUM/GENU VARUM

26. BURSITIS OF KNEE

27. PATELLO FEMORAL JOINT Patella is the largest sesamoid bone
ARTICULATION:
Patella is attached to the patellar surface on distal Femur.
During Flexion , from Full Extension patella slides downwards and rest in intercondylar notch
During Extension,from Full Flexion patella slides upwards

28. ARTCULATING SURFACES

29. Q ANGLE QUADRICEPS ANGLE( Q ANGLE ):
The angle formed by resultant vector of Quadriceps and the pull of ligamentum patella
It is found by drawing two lines
1.From ASIS to midpoint of Patella
2.From Tibial tubercle to midpoint of Patella
The normal angle is 15 degree
When the angle is large -----Lateral pull on patella is increased.

30. Q ANGLE

31. PROBLEMS OF PATELLOFEMORAL JOINT
PATELLA ALTA:
High riding of patella(elevation),there is lateral stress to patella and instability.
CONDROMALACIA PATELLA:
Softening of articular cartilage of Patellofemoral joint.
Later stage fibrillation and thining of cartilage occurs and subchondral bone exposed.

32. PATELLA ALTA / CMP

33. PATELLAR DISLOCATION