The document provides an overview of the biomechanics of the knee joint. It discusses the tibiofemoral and patellofemoral joints, including the articulating surfaces, menisci, ligaments, muscles, and movements. It describes problems that can occur in each joint like meniscus injuries, ACL tears, patella alta, and condromalacia patellae. Key concepts covered are the screw home mechanism of knee locking in extension, the Q-angle of the patella, and how joint reaction forces increase with flexion angle during stance and swing phases of gait.

1. BIOMECHANICS OF KNEE
DR SHARANPRASAD A H

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. 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

10. LIGAMENTS

11. LIGAMENTS

12. 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

13. LIGAMENTS

14. 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
SEMIMEMBRANOSUS
POSTERIOR LATERAL ARCUATE POPLITEAL POPLITEUS

15. 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

16. 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

17. 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

18. 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

19. 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.

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

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

22. 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

23. MENISCUS INJURY

24. GENU VALGUM/GENU VARUM

25. 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

26. ARTCULATING SURFACES

27. 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.

28. Q ANGLE

29. 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.

30. PATELLA ALTA / CMP

31. PATELLAR DISLOCATION

32. KNEE FLEXION-EXTENSION ARC
 SAGITTAL PLANE
 FLEXION
 EXTENSION
 DIVIDED INTO 3 RANGES
 SCREW HOME ARC
 FUNCTIONAL ARC
 DEEP FLEXION ARC

33. SCREW HOME ARC
 5 – 10
 HERE KNEE IS LOCKED .
 THE FEMUR IS IN NEUTRAL ALIGNMENT WITH THE TIBIA
 FEMUR STARTS TO INTERNALLY ROTATE AS THE KNEE IS EXTENDED

34. FUNCTIONAL ARC
 10 – 120
 EXTERNAL ROTATION OF FEMUR
 DURING FLEXION, LATERAL CONDYLE BEGINS TO SLIDE POSTERIORLY WHERE AS
MEDIAL CONDYLE MAINTAIN ITS POSITION ON THE TIBIA
 CONSIDERED AS ACTIVE RANGE

35. DEEP FLEXION ARC
 120 – 140
 FURTHER EXTERNAL ROTATION OF FEMUR
 BOTH CONDYLES SLIDE POSTERIORLY
 THE ROLLBACK AND SLIDE ACHIEVES FULL FLEXION
 CALLED PASSIVE RANGE

36. JOINT REACTION FORCE
 THESE FORCE INCREASE WITH KNEE FLEXION ANGLE AND DEPENDS ON WETHER
THE LEG IS IN STANCE OR SWING PHASE
 JOINT REACTION FORCE IS MAXIMUM DURING FLEXION
 BUT KNEE FLEXION VARIES
 20 WALKING IN SMOOTH SURFACE
 60 ASCENDING STAIRS
 85 DESCENDING STAIRS

37. THANK YOU