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Ithaca College
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The Knee
Scroll down to follow a complete dissection of the knee joint or click below for direct viewing:
Click here to skip to review
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Follow the dissection manual closely for instructions on skinning the knee and observation of the superficial features of the knee.
FIG. 2-1 : ANTEROMEDIAL KNEE (back to top)
Follow the instructions in your manual for
skinning the lower leg. After you have completed skinning, you will be able
to identify the attachment of the slendor muscles on the medial aspect of
the tibia. This triangular shaped muscular attachment is composed of the tendons
of sartorius,
gracilis, and semitendinosus muscles.
A common way to rememeber this attachment is the acronym for sargeant, SGT,
as noted on figure 2-1. This attachment is known as the pes
ancerine......
Each muscle in this group has a unique proximalttachmeachment.
FIG. 2-2 : MEDIAL KNEE (back to top)
Once you have identified the pes ancerine, you will
be able to detach the sartorius, gracilis, and semitendinosus at this location.
After reflecting these tendons, you will need to carefully remove the deep
fascia. Once this is completed, you will be able to see the tibial
or medial collateral ligament (MCL). This "fan
shaped" thick band is one of four major ligaments of the knee which provide
stabilization. The MCL provides medial stabilization to prevent the knee from
buckling inward. Using your probe, you will be able to locate the medial meniscus
where the deeper portion of the MCL makes its attachment. (We will discuss
the menisci more in depth later). Also on this figure, you can see the anterior
attachment of the soleus
muscle, an ankle plantarflexor, which lies deep
to the gastrocnemius muscle.
FIG. 2-3 : POSTEROLATERAL KNEE (back to top)
On the lateral aspect of the knee, locate the IT
band. The IT band attaches on the anterior lateral condyle of the
tibia. After you cut the IT band and the biceps
femoris tendons, you will reveal the fibular
or lateral collateral ligament (LCL) within the deep fascia. The LCL,
unlike the MCL, is a straplike ligament about the width of a pencil. Unlike
the MCL, the LCL passes over the lateral meniscus to attach to the head of
the fibula. The LCL provides lateral stabilization to prevent the knee from
buckling outward
FIG. 2-4 : POSTERLATERAL LIGAMENTS (back to top)
Another important part of the knee complex is the articulation
between the tibia and the fibula. Deep to the LCL, you will see where the
tibia and fibula meet. Along that articulation are two small, but strong ligaments
- the medial and lateral
tibiofibular ligaments. These ligaments maintain a firm articulation
to prevent excessive movement between these two bones. Also visible on this
illustration is the posterior cruciate ligament, which we will discuss later.
Click here
to see a magnified view of this.
FIG. 2-5 : POSTERIOR KNEE (back to top)
The next step of your dissection of the knee joint is to remove the remaining
adipose, vessels, and nerves of the popliteal fossa. Also you will need to
remove or reflect the remaining musculature and the joint capsule. Once you
have cleared away the excess soft tissue, you will be able to clearly identify
the fibers of the posterior
cruciate ligament or PCL. The PCL is a strong twisting ligament which
attaches from the femur to posterior tibia. This prevents anterior displacement
of the femur or posterior displacement of the tibia.
FIG. 2-6 : ANTERIOR KNEE (back to top)
Following the location of the PCL, we will view the knee from the anterior
aspect. In order to view the interior knee, you will need to reflect the patella
proximally, severing the tendon at the tibial tuberosity. You will also need
to penetrate and remove the synovial capsule. Follow the instructions in your
manual for more in depth instructions. Once you have removed this tissue,
you will note that the knee is still firmly attached by the remaining four
ligaments. By placing the knee in flexion, you will clearly see the anterior
cruciate ligament or ACL. The ACL attaches from the femur to the anterior
tibia preventing posterior displacement of the femur or anterior displacement
of the tibia.
FIG. 2-7 : ANTERIOR KNEE LIGAMENTS (back to top)
Figure
2-7 illustrates the knee in flexion. As you can see, there is minimal
articulation between the joint surfaces in this position. While in flexion,
the knee allows slight rotation at the expense of stability. In this position,
the PCL is taut, preventing the femur from sliding anterior on the tibial
plateau. The oppostie situation occurs when the knee is maximally extended.
This position would be known as the "close packed" position where
the knee is "locked". In full extension there is maximal contact
between the articular surfaces of the tibia and the femur. It is in this postion
when the ACL becomes taut and prevents further extension. Inorder to attain
full extension, the knee experiences a minor rotational component which is
known as the "screw-home" mechanism, accounting for maximal stabiltiy
in this position. Also in this figure, notice the smooth and shiny articular
surfaces, characteristic of healthy cartilage, free from arthritis and other
joint pathologies.
FIG. 2-8 : TIBIAL PLATEAU (back to top)
For a more in depth view of the tibial plateau, we have severed the ligaments
of the knee at the femur and detached the leg and ankle from the thigh. Figure
2-8 is a superior view of the tibial plateau. This figure is oriented
with the anterior tibia at the bottom of the screen. Notice how the ACL
and PCL twist around
one another. Observe the cut ends of the ligaments and picture how they would
attach on the femur. Now review the discussion form the previous text to understand
the function of these important ligaments. Also notice the association of
the LCL and MCL.
FIG. 2-9 : CUT KNEE LIGAMENTS (back to top)
Study the menisci or semilunar cartilages in figure
2-9. These two cartilagenous rings have resilient properties which
allow the menisci to act as shock absorbers for the knee. The menisci help
to protect your knee from the compressive forces undergone in day to day activity.
The "C" shaped medial meniscus is firmly attached to the tibia and
the MCL. On the other hand, the oval shaped lateral meniscus is freely mobile,
without attachment to the LCL. Click here
to see the specific attachment sites on the tibial plateau.
Home
Highlighted Knee Structures in Review
To view, click on the desired structure below:
ACL |
lateral tibiofibular ligament |
sartorius muscle |
MCL |
semitendinosus muscle |
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gracilis muscle |
medial tibiofibular ligament |
soleus muscle |
IT band |
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LCL |
PCL |
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