Lecture 7. The knee joint It is the largest joint in the body & one of the more complex joints in...
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Knee joint Lecture 7
Lecture 7. The knee joint It is the largest joint in the body & one of the more complex joints in the body. Because it is supported and maintained entirely
The knee joint It is the largest joint in the body & one of
the more complex joints in the body. Because it is supported and
maintained entirely by muscles and ligaments with no bony stability
Because it is frequently exposed to severe stresses and strains it
should be no surprise that it is one of the most frequently injured
joints in the body.
Slide 3
The knee joint .. Joint type??? synovial hinge joint flexion
and extension (0 degrees - 120 to 135 degrees of flexion). Modified
hinge ????!!! Rotation accessory motion !!! From 0 degrees of
extension there are approximately 120 to 135 degrees of flexion.
knee joint is not a true hinge because it has a rotational
component. This rotation is not a free motion but an accessory
motion that accompanies flexion and extension.
Slide 4
The knee joint .. All three types of arthrokinematic motions
are used during knee flexion and extension ??!!!!!!! The articular
surface of the femoral condyles is much greater than that of the
tibial condyles. the articular surface of the femoral medial
condyle is longer than that of the lateral condyle. Roll Slide
Spin
Slide 5
The convex femoral condyles move on the concave tibial
condyles, or the other way around depending upon whether it is an
open- or closed-chain activity. If the femur rolled on the tibia
from flexion to extension, the femur would roll off the tibia
before the motion was complete. Therefore, the femur must glide
posteriorly on the tibia as it rolls into extension. It should also
be noted that the articular surface of the femoral medial condyle
is longer than that of the lateral condyle. As extension occurs,
the articular surface of the femoral lateral condyle is used up
while some articular surface remains on the medial condyle.
Therefore, the medial condyle of the femur must also glide
posteriorly to use all of its articular surface. It is this
posterior gliding of the medial condyle during the last few degrees
of weight- bearing extension (closed chain action) that causes the
femur to spin (rotate medially) on the tibia.
Slide 6
screw-home mechanism Open-chain action (Non-weight-bearing) the
tibia rotates laterally on the femur lock the knee in extension
With the knee fully extended, an individual can stand for a long
time without using muscles. The knee must be unlocked by the femur
rotating laterally on the tibia for knee flexion to occur. It is
this small amount of rotation of the femur on the tibia, or vice
versa, that keeps the knee from being a true hinge joint. Because
this rotation is not an independent motion, it will not be
considered a knee motion. Looking at the same spin, or rotational,
movement during non weight-bearing extension
Slide 7
screw-home mechanism
Slide 8
The patellofemoral joint The posterior surface of the patella
is smooth and glides over the patellar surface of the femur. It is
the articulation between the femur and patella.
Slide 9
Patella increase the mechanical advantage (to protect the knee
joint) lengthening the moment arm By placing the patella between
the quadriceps tendon and the femur, the action line of the
quadriceps muscles is farther away. Hence, the moment arm is
lengthened, which allows the muscle to have greater angular force.
Without the patella, the moment arm would be smaller and much of
the force of the muscle would be a stabilizing force directed back
into the joint.
Slide 10
is the angle between the quadriceps muscle, primarily the
rectus femoris muscle, and the patellar tendon. It is determined by
drawing a line from ASIS ??!!!to the midpoint of the patella and
from the tibial tuberosity to the midpoint of the patella. The
angle formed by the intersecting of these lines represents the Q
angle Although the rectus femoris attaches to the anterior inferior
iliac spine (AIIS), the ASIS lies just above the AIIS and is easier
to palpate. The Q angle ( patellofemoral angle)
Slide 11
This angle ranges from 13 to 18 degrees in normal individuals
in knee extension, and tends to be greater in females!!! Why???!!!
A greater angle in females is associated with the fact that females
tend to have a wider pelvis.
Slide 12
Ligaments and other structures The knee is held together not by
its bony structure but by ligaments and muscles. Knee Ligaments: -
The cruciate ligaments - The collateral ligaments
Slide 13
The cruciate ligaments Intra-capsular ligaments. Located
between the medial and lateral condyles, the cruciates cross each
other obliquely. Anterior cruciate ligament Posterior cruciate
ligament The cruciates provide stability in the sagittal plane
(cruciate means resembling a cross in Latin). They are named by
their attachment on the tibia. The anterior cruciate ligament
attaches to the anterior surface of the tibia in the inter-condylar
area just medial to the medial meniscus. It spans the knee
laterally to the posterior cruciate ligament and runs in a superior
and posterior direction to attach posteriorly on the lateral
condyle of the femur.
Slide 14
Anterior cruciate ligament It keeps the femur from being
displaced posteriorly on the tibia/ the tibia from being displaced
anteriorly on the femur It tightens during extension, preventing
excessive hyperextension of the knee. The posterior cruciate
ligament attaches to the posterior tibia in the inter-condylar area
and runs in a superior and anterior direction on the medial side of
the anterior cruciate ligament. It attaches to the anterior femur
on the medial condyle. To summarize these attachments, the anterior
cruciate runs from anterior tibia to posterior femur, and the
posterior cruciate runs from posterior tibia to anterior femur.
When the knee is partly flexed, the anterior cruciate keeps the
tibia from being moved anteriorly.
Slide 15
posterior cruciate ligament It keeps the femur from being
displaced anteriorly on the tibia/ the tibia from being displaced
posteriorly on the femur. It tightens during flexion and is injured
much less frequently than the anterior cruciate ligament.
Slide 16
Collateral ligaments The collateral ligaments provide stability
in the frontal plane. - Medial collateral ligament - Lateral
collateral ligament
Slide 17
Collateral ligamnets Located on the sides of the knee are the
collateral ligaments. The medial collateral (tibial collateral)
ligament is a flat, broad ligament attaching to the medial condyles
of the femur and tibia. Fibres of the medial meniscus are attached
to this ligament, which contributes to frequent tearing of the
medial meniscus when there is excessive stress to the medial
collateral ligament. On the lateral side is the lateral collateral,
or fibular collateral, ligament. It is a round, cordlike ligament
that attaches to the lateral condyle of the femur and runs down to
the head of the fibula, independent of any attachment to the
lateral meniscus. It protects the joint from stresses to the medial
side of the knee. It is quite strong and not commonly injured
Slide 18
Medial collateral ligament Tibial collateral ligament The
medial collateral ligament, providing medial stability, prevents
excessive motion from a blow to the lateral side of the knee.
Slide 19
Fibular collateral ligament. It provides stability to the
medial side. Lateral collateral ligament On the lateral side is the
lateral collateral. It is a round, cordlike ligament that attaches
to the lateral condyle of the femur and runs down to the head of
the fibula, independent of any attachment to the lateral meniscus.
It protects the joint from stresses to the medial side of the knee.
It is quite strong and not commonly injured Because their
attachments are offset posteriorly and superiorly to the axis of
flexion, the collateral ligaments become tight during extension,
contributing to the stability of the knee, and slack during
flexion.
Slide 20
Knee Menisci Medial and lateral meniscus They are two half
moon, wedge-shaped fibrocartilage disks located on the superior
surface of the tibia and are designed to absorb shock. Because they
are thicker laterally than medially and the proximal surfaces are
concave, the menisci deepen the relatively flat joint surface. The
medial meniscus, perhaps because of its attachment to the medial
collateral ligament, is more frequently torn. The meniscus (plural:
menisci, from the Greek for "crescent") is the curve in the upper
surface of a liquid close to the surface of the container or
another object, caused by surface tension. It can be either convex
or concave. A convex meniscus occurs when the molecules have a
stronger attraction to each other (cohesion) than to the material
of the container (adhesion) Greekcrescentsurface tensionconvex or
concavecohesionadhesion a meniscus (from Greek meniskos, "crescent"
[1] ) is a crescent- shaped fibrocartilaginous structure that, in
contrast toarticular disks, only partly divides a joint
cavity.Greek [1]fibrocartilaginousarticular disks It usually refers
to either of two specific parts of cartilage of the knee: The
lateral and medial menisci. Both are cartilaginous tissues that
provide structural integrity to the knee when it undergoes tension
and torsion. The menisci are also known as 'semi-lunar' cartilages
referring to their half-moon "C" shape a term which has been
largely dropped by the medical profession, but which led to the
menisci being called knee 'cartilages' by the lay
public.cartilagelateralmedial
meniscicartilaginoustensiontorsion
Slide 21
Knee Menisci
Slide 22
Knee Bursa The purpose of a bursa is to reduce friction, and
approximately 13 are located at the knee joint. They are needed
because the many tendons located around the knee have a relatively
vertical line of pull against bony areas or other tendons.
Slide 23
Knee Bursa
Slide 24
Slide 25
The Popliteal space The popliteal space is the area behind the
knee, and it contains important nerves (tibial and common peroneal)
and blood vessels (popliteal artery). This diamond-shaped fossa is
bound superiorly on the medial side by the semitendinosus and
semimembranosus muscles and by the biceps femoris muscle on the
lateral side. The inferior boundaries are the medial and lateral
heads of the gastrocnemius muscle.
Slide 26
The Popliteal space
Slide 27
The pes anserine It is a muscle group is made up of the
(SGS)!!! They all cross the knee posteriorly and medially, then
join together to have a common distal attachment on the anterior
medial surface of the proximal tibia. Orthopedic surgeons sometimes
alter this common attachment to provide for medial stability to the
knee. The pes anserine (Latin, meaning goose foot)
Slide 28
Muscles of the knee:
Slide 29
The quadriceps muscles!!!!
Slide 30
The popliteus muscle is a one-joint muscle located posteriorly
at the knee in the popliteal space deep to the two heads of the
gastrocnemius muscles. It originates on the lateral side of the
lateral condyle of the femur and crosses the knee posteriorly at an
oblique angle to insert medially on the posterior proximal tibia.
Because it spans the knee posteriorly, it flexes the knee. It is
credited with unlocking the knee, or initiating knee flexion. The
gracilis and sartorius muscles span the knee medially, contributing
greatly to medial stability. The gastrocnemius and hamstring
muscles provide posterior stability both medially and laterally,
and the quadriceps muscles provide anterior stability.