BIOMECHANICS OF KNEE

U.RADHAKRISHNAN.M.P.T

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

INTRODUCTION

KNEE COMPLEX

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

TIBIOFEMORAL JOINT

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

MENISCI

MENISCUS

Stability & Mobility Function STABILITY: Deepens articular surface Keeps the joint surface tight Distribute the load MOBILITY: Reduces friction

FUNCTIONS OF MENISCI

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

JOINT CAPSULE & BURSAE

BURSAE

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

LIGAMENTS

LIGAMENTS

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

LIGAMENTS

LIGAMENTS

STABILITY LIGAMENTS MUSCLESMEDIAL STABILITY MEDIAL COLLATERAL SEMIMEMBRANOSUSLATERAL STABILITY LATERAL COLLATERAL POPLITEUS.IT BANDANTERIOR STABILITY ANTERIOR CRUCIATE QUADRICEPS,

PATELLAPOSTERIORSTABILITY POSTERIOR CRUCIATE BICEPS

FEMORIS,POPLITEUSANTEROMEDIAL MEDIAL

COLLATERAL,ANTERIOR CRUCIATE

QUADRICEPS

ANTERIOLATERAL LATERAL COLLATERAL,POSTERIOR CRUCIATE

POSTERIOR MEDIAL OBLIQUE POPLITEAL LIGAMENT

SEMIMEMBRANOSUS

POSTERIOR LATERAL ARCUATE POPLITEAL POPLITEUS

STABILITY OF KNEE

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

ANATOMIC AXIS

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

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

MOVEMENTS

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

ARTHROKINEMATICS

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.

LOCKING AND UNLOCKING

EXTENSORS

QUADRICEPS

The efficiency of Quadriceps depends on PATELLA,it increases the moment arm

Supports the body weight

Resist the force of gravity

MUSCLES

FLEXORS

HAMSTRINGS

Work more effectively in Knee if they are lengthened over a Flexed hip

MUSCLES

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

PROBLEMS OF TIBIOFEMORAL JOINT

MENISCUS INJURY

GENU VALGUM/GENU VARUM

BURSITIS OF KNEE

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

PATELLO FEMORAL JOINT

ARTCULATING SURFACES

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.

Q ANGLE

Q ANGLE

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.

PROBLEMS OF PATELLOFEMORAL JOINT

PATELLA ALTA / CMP

PATELLAR DISLOCATION