Transcript Knee Lecture

Knee Joint
• actually 2 joints within the
articular capsule
– tibio-femoral
– patello-femoral
– the superior fibulo-tibial
joint is also near
– modified hinge joint
• flexion and extension is
primary motion
• some rotation is possible
when the knee is flexed
epicondyles
condyles
patella
tibial plateaus
intercondylar notch
Anterior
Posterior
tibial tuberosity
Transverse
Anterior
Ligamentous Support
Menisci
Cruciate
Ligaments
Collateral
Ligaments
Other
Ligaments
Menisci
• The menisci are discs of fibrocartilage attached to tibial
plateaus. They are thicker along the periphery.
The lateral meniscus
is smaller and more
mobile than the
medial meniscus. The
inner portion of the
menisci are avascular.
The outer portion has
some blood supply,
making healing of
tears possible.
lateral
medial
Menisci Function
• increases stability by
deepening tibial plateaus
• decreases friction by 20%
• increases contact area by 70%
• absorbs shock
– removal of menisci does NOT
preclude normal motion, but
• increase wear on articulating
surfaces
• increase chance of developing
degenerative joint disease
Collateral
Ligaments
lateral (fibular)
medial (tibial)
Collateral
Ligaments
prevents abduction and
adduction movement
of the knee
Additional
Ligamentous
Support
•iliotibial band
thick, strong band of
tissue connecting
tensor fascia latae to
femur and tibia
Cruciate
Ligaments
cruciate -- ‘cross’
ligaments form an ‘X’
or cross within the joint
named for their TIBIAL
attachments
Anterior Cruciate (ACL)
Posterior Crucuate (PCL)
shorter and stronger than
ACL
The ACL prevents the
femur from sliding
posteriorly on the tibia
or the tibia from sliding
anteriorly on the femur.
F
E
M
U
R
PATELLA
The PCL prevents the
femur from sliding
anteriorly on the tibia or
the tibia from sliding
posteriorly on the femur.
T
I
B
I
A
The PCL prevents the tibia from sliding
posteriorly on the femur.
Posterior
Anterior
Cruciates During Flexion/Extension
Note: the cruciate
ligaments also
limit rotation
Patello-femoral Joint
• articulation of the
patella and femur
• the patella is a true
sesamoid bone
• posterior surface of
the patella is
covered with thick
hyaline cartilage
• the patella slides
within the trochlear
groove
Functions of Patello-femoral Joint
with patella
(1) increases angle of pull of
quads on tibia, improves the
ratio of motive:resistive
torque by 50%
(2) centralizes divergent tension
of quads into a single line of
action
(3) some protection of anterior
aspect of knee
without patella
Q-Angle
The Q-angle is the angle formed
by a line from the anterior
superior spine of the ilium to
the middle of the patella and a
line from the middle of the
patella to the tibial tuberosity.
Males typically have Q-angles
between 10 to 14o, females
between 15-17o.
Atypical Q-angles
bowleggedness
knock-knees
Knee Rotation
(Locking Your Knee)
Extension
• Six to 30 degrees of internal
rotation of the tibia on the
femur occurs through 90
degrees of knee flexion.
Flexion
External
Rotation
Internal
Rotation
1 The femoral condyles do not have the same diameters, this helps
cause internal rotation when the knee is flexed and external
rotation when the knee is extended.
2 The lateral condyle slides more than medial condyle.
3 The anterior cruciate ligament becomes taut just prior to the
rotation, this may help force a rotation of the femur on the tibia.
Knee Musculature
many 2 joint muscles
primary movements
- flexion and extension
- hams & quads,
respectively
medial and lateral
rotation possible
necessary for screwhome mechanism
Knee Flexion
Hamstrings
cross hip and knee
biceps femoris
semitendinosus
semimembranosus
gastrocnemius
cross knee and ankle
popliteus
Knee Extension - Quadriceps
rectus femoris
vastus lateralis
vastus medialis
vastus intermedius
quadriceps tendon
patellar ligament
Lateral Rotation
biceps femoris
attaches to lateral aspect of knee
Medial Rotation
semitendinosus
semimembranosus
popliteus
attach to medial aspect of knee
Common Knee Injuries
• one of the most commonly injured joints
– lack of bony and muscular support
– positioned between the 2 longest bones
– weight bearing and locomotion functions
• often tear or stretching of soft tissue
Ligament Injuries
• ACL
– more prevalent than PCL injuries
– forces directed from posterior side of leg
• PCL
– forces directed from anterior side of leg
– forced flexion of knee w/external rotation
• wrestling and football
Ruptured ACL Knee
Intact Knee with ACL
& PCL
Mechanisms of ACL injury
1) attempting a rapid cutting maneuver
with foot in contact with the ground and
knee flexed (problem exacerbated if an
external force applied to knee during
this movement)
2) knee hyperextension with internal
tibial rotation
Example
backward falling skier - boot
and skis accelerate forward creating an
anterior drawer mechanism
Gender issues related to ACL injuries
females more likely to sustain an ACL injury than males
soccer - 2.6X
basketball - 5.75X
wider pelvis
greater flexibility
less-developed musculature
hypoplastic vastus medialis obliquus
narrow femoral notch
genu valgum
external tibial torsion
PCL Injuries
When the knee is forcefully twisted or hyperextended BUT other
ligaments are usually injured or torn, before the posterior
cruciate ligament (PCL) is torn
Most common mechanism for PCL alone to be injured is from a
direct blow to the front of the knee while the knee is bent.
Automobile accident
1. Automobile strikes another and stops suddenly
2. Front passenger or driver slides forward.
3. Bent knee hits the dashboard just below the knee cap forcing
tibia backwards on the femur tearing PCL.
The same force can occur during a fall on the bent knee, where the
force of the fall on the tibia pushes it back against the femur
and tears the posterior cruciate ligament (PCL).
Common mechanism of
PCL injury in football is
being tackled while the
knee is fully extended.
When the tibia is
displaced too much in the
posterior direction the
PCL may rupture.
Ligament Injuries
L
• injuries to MCL more prevalent
than LCL
• MCL
– foot planted and force applied to the
lateral side of knee
• football
M
Meniscus Injuries
• most common injury in the knee
• tearing is most common
• medial side injured more often
– medial meniscus more secured
– foot planted with excessive rotation
Iliotibial Band
Syndrome
• IT-band
– thick strong band of
ligamentous tissue
– connects tensor fascia latae
to the lateral condyle of the
femur and the lateral
tuberosity of the tibia
• IT-band rubs against the
lateral femoral condyle
when there is excessive
tension
• excessive pronation increases internal rotation of the
tibia, which accentuates the friction of the IT band and
femoral condyle
• tibial alignment and size of femoral condyle may also
contribute to the development of this condition