Knee Kinematics and Kinetics - Buffalo

Patellar K

• Patella directly conta

in flexion

• Patella acts as the fu
• It is said to be “latera

– Greater surface area
side as opposed to th

Kinematics

acts femoral condyles

ulcrum
al side dominant”

a of contact on the lateral
he medial

Patellar K

--Figure from Fulkerson, D

Kinematics

Disorders … 1997 3rd ed.

Compressive Fo

Figure from Fulkerson
1997

orces of Patella

Patellar K

• There are predictable a

between patella and fem
change with degree of fl

--figure from Fulkerson 19

Kinematics

areas of contact
moral condyles that
lexion:

997

Patellar Ki

Forces acting on the P

• Laterally- lateral retin

lateralis m., ilio

• Medially- medial retin

medialis m.

• Superior- Quadriceps

tendon

• Inferior- Patellar tend

inematics 2

Patella:
naculum, vastus
otibial tract
naculum and vastus

s via quadriceps

don

Patellar Ki

Figure from Fulkerson, 1997

inematics 3

Patellar Ki

• Sum of forces acting

– Determine movemen

• Additional forces con

– Friction forces, comp
translational forces a
forces from soft tissu

inematics 4

g in the four directions

nt pattern of the knee joint

nsidered are:

pressive forces, torques,
and internal stabilizing
ues

Patellar Ki

Q-angle :

• Angle formed at the k

– By connecting a line
iliac crest to the cent

– And a second line fro
patella to the center o
insertion into the tibia

inematics 5

knee joint

from the anterior superior
ter of the patella
om the center of the
of the patellar tendon
al tubercle

Q-An

Angle

Q-Angle

Q-angle of 12 to 15 degre
while patients with patella
have a Q-angle as high as

Henry J.H., Goletz T.H., and William
Release in Patellofemoral

Subluxation.” Am J of Sports Med
129.

e (cont’d)

ees is considered normal;
ar subluxation may
s 30 degrees

mson B. “Lateral Retinacular
d. Vol. 14 No.2 1986 pp121-

Patellar ma

• Generally associated

– Lateral retinaculum
– Hamstrings
– Iliotibial band
– Quadriceps
– Hip rotators
– Achilles tendon

alalignment

d with tightness of

Knee Kin

nematics

The "Screw-Ho

• Rotation between the

– Occurs automatically
0o and 20o of knee fle

• SHM is considered a

stability for standing

ome” mechanism

e tibia and femur

y between full extension
exion

key element to knee
upright

“Screw-Home

• Tibia

– Internal rotation during
– External rotation during

• External rotation

– Occurs during the termin
• Difference in radius of cur

lateral condyle

– Results in tightening of b
• Locks the knee
• Tibia is in the position of m

femur

e” mechanism

g the swing phase
g the stance phase

nal degrees of knee extension

rvature of the medial and smaller

both cruciate ligaments

maximal stability with respect to the

Ligament Attachm
Joi

ments in the knee
int

“Screw-Home”

• During Knee extensio

– Tibia rolls anteriorly,
PCL elongates

– PCL's pull on tibia
causes it to glide
anteriorly on femur

” mechanism 2

on

Axial View of the
Knee of Right Leg

“Screw-Home”

• During the last 200 of

knee extension

– Anterior tibial glide
persists on the tibia's
medial condyle
• Because its articular

surface is longer in th
dimension than the la
condyle‘s

” mechanism 3

of

s

hat
ateral

“Screw-Home”

• Prolonged anterior gl

on the medial side

– Produces external tib
rotation

– The "screw-home"
mechanism

” mechanism 4

glide

bia

“Screw-Home”

• When the knee begin

flex from a position o
extension

– Tibia rolls posterior,
elongating ACL

– ACL's pull on tibia ca
it to glide posterior

– Glide begins first on t
longer medial condyle

” mechanism 5

ns to
of full

auses
the
le

“Screw-Home”

• Between 00 extension

and 200 flexion

– Posterior glide on the
medial side produces
• Relative tibial internal

rotation

• A reversal of the screw-

home mechanism

” mechanism 6

Internal Tibial
Rotation

New flexion and ex

• A fixed flexion and

theory [based on 3
knee]

• Replacing the clas

variable flexion an
[based on observa
plane]

xtension axis theory

d extension axis
3-D observation of

ssic concept of the
nd extension theory
ation in the sagittal

Flexion-Extens

• ”it has recently been sh

the knee is FIXED withi

articular surfaces of the
profile”

(Hollister et al. 1994, H
1995)

sion Kinematics

hown that the F-E axis of
hin the femur and that the

e condyles are circular in

Hollerbach and Hollister,

Flexion-Extens

sion Kinematics

Kinematics in

Osteoarthrosis

THE

END