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Transcript
Interactive Knee:
Cruciate Ligaments
By Primal Pictures
EDITOR'S NOTE: The following is a small sample of the Interactive Knee
CD in the ground breaking Primal Pictures 3-D Anatomy CD ROM series.
The cruciate ligaments are two in
number. They are named anterior
and posterior with regard to the
positions of their attachments on the
tibial plateau; the anterior cruciate
ligament being attached to the
anterior intercondylar area of the
tibial plateau, and the posterior
cruciate being attached to the
posterior intercondylar area of the
tibial plateau. They are named
cruciate ligaments because they
cross each other (like the limbs of
the letter X). Both cruciate ligaments
are situated within the capsule of the
knee joint. However they are not
within the synovial cavity of the knee
joint. The cruciate ligaments receive a sensory innervation from the genicular
branches of the tibial, common peroneal and obturator nerves. Sensations
subserved by these sensory nerves include both pain and proprioception, and
correspondingly both pain receptors and mechano-receptors have been
identified within the cruciate ligaments.
The cruciate ligaments are vascularized structures; the blood supply of the
cruciate ligaments being derived from the genicular branches (principally the
middle genicular branch) of the popliteal artery. Thus hemarthrosis is an
important clinical feature of cruciate rupture.
The function of the anterior cruciate ligament is to resist posterior displacement
of the femur on the tibia.
The function of the posterior cruciate ligament is to resist anterior displacement
of the femur on the tibia.
The anterior cruciate ligament lies entirely within the capsule of the knee joint
but extrasynovially. Its inferior attachment (i.e., tibial attachment ) is to a facet
on the medial part of the anterior intercondylar area of the tibial plateau. Its
superior attachment is to a facet on the posterior part of the medial surface of
the lateral femoral condyle. Thus the anterior cruciate ligament runs obliquely
upwards, posteriorly and laterally from its tibial attachment to its femoral
attachment. However, the fibers arising most anteriorly on the tibial plateau are
attached most posteriorly on the lateral femoral condyle, and the fibers arising
most posteriorly on the tibial plateau are attached most anteriorly on the femur.
As a result of this arrangement the anterior cruciate ligament is slightly twisted
about its long axis. Because of this helical structure, in a functional sense the
anterior cruciate ligament appears to consist of two bands although
morphologically it is a single structure. These are referred to as the
anteromedial and posterolateral bands. Of the two, the posterolateral
component makes up the greater part of the ligament.
Knee flexion is associated with a greater degree of tautness in the
anteromedial component, while extension results in a greater degree of
tautness in the posterolateral component. Another consequence of the spiral
nature of the anterior cruciate ligament is that tension in the ligament is
increased during internal rotation of the joint, while external rotation of the joint
results in a decrease in ligament tension.
In the adult, the anterior cruciate ligament is 38mm long and 10mm wide on
average.
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