The posterior cruciate ligament is one of the four major ligaments of the knee.
It connects the posterior intercondylar area of the tibia to the medial condyle
of the femur. This configuration allows the PCL to resist forces pushing the
tibia posteriorly relative to the femur. The PCL is an intracapsular ligament
along with the anterior cruciate ligament because it lies deep within the
knee joint. They are both isolated from the fluid-filled synovial cavity, with
the synovial membrane wrapped around them. The PCL gets its name by attaching
to the posterior portion of the tibia. Structure
The PCL is located within the knee joint where it stabilizes the articulating
bones, particularly the femur and the tibia, during movement. It originates
from the lateral edge of the medial femoral condyle and the roof of the
intercondyle notch then stretches, at a posterior and lateral angle, toward the
posterior of the tibia just below its articular surface.
Function Although each PCL is a unified unit,
they are described as separate anterolateral and posteromedial sections
based off where each section's attachment site and function. During
knee joint movement, the PCL rotates such that the anterolateral section
stretches in knee flexion but not in knee extension and the posteromedial
bundle stretches in extension rather than flexion.
The function of the PCL is to prevent the femur from sliding off the anterior
edge of the tibia and to prevent the tibia from displacing posterior to the
femur. The posterior cruciate ligament is located within the knee. Ligaments
are sturdy bands of tissues that connect bones. Similar to the anterior cruciate
ligament, the PCL connects the femur to the tibia.
Clinical significance Common causes of injuries are direct
blows to the flexed knee, such as the knee hitting the dashboard in a car
accident or falling hard on the knee, both instances displacing the tibia
posterior to the femur. An additional test of posterior cruciate
ligament injury is the posterior sag test, where, in contrast to the drawer
test, no active force is applied. Rather, the person lies supine with the
leg held by another person so that the hip is flexed to 90 degrees and the knee
90 degrees. The main parameter in this test is step-off, which is the shortest
distance from the femur to a hypothetical line that tangents the
surface of the tibia from the tibial tuberosity and upwards. Normally, the
step-off is approximately 1 cm, but is decreased or even absent or inverse in
injuries to the posterior cruciate ligament. The posterior drawer test is
one of the tests used by doctors and physiotherapists to detect injury to the
PCL. Patients who are suspected to have a posterior cruciate ligament injury
should always be evaluated for other knee injuries that often occur in
combination with an PCL injuries. These include cartilage/meniscus injuries,
bone bruises, ACL tears, fractures, posterolateral injuries and collateral
ligament injuries. There are four different grades of
classification in which medical doctor’s classify a PCL injury: Grade I, the PCL
has a slight tear. Grade II, the PCL ligament is minimally torn and becomes
loose. Grade III, the PCL is torn completely and the knee can now be
categorized as unstable. Grade IV, the ligament is damaged along with another
ligament housed in the knee. With these grades of PCL injuries, there are
different treatments available for such injuries.
= Mechanism= In this position, the PCL functions to
prevent movement of the tibia in the posterior direction and to prevent the
tilting or shifting of the patella. However, the respective laxity of the
two sections makes the PCL susceptible to injury during hyperflexion,
hyperextension, and in a mechanism known as a dashboard injury. Because ligaments
are viscoelastic) they can handle higher amounts of stress only when the load is
increased slowly. When hyperflexion and hyperextension occur suddenly in
combination with this viscoelastic behavior, the PCL deforms or tears. In
the third and most common mechanism, the dashboard injury mechanism, the knee
experiences impact in a posterior direction during knee flexion toward the
space above the tibia. These mechanisms occur in excessive external tibial
rotation and during falls that induce a combination of extension and adduction
of the tibia, which is referred to as varus-extension stress, or that occur
while the knee is flexed. = Treatment=
It is possible for the PCL to heal on its own. Surgery is usually required in
complete tears of the ligament. Surgery usually takes place after a few weeks,
in order to allow swelling to decrease and regular motion to return to the
knee. A procedure called ligament reconstruction is used to replace the
torn PCL with a new ligament, which is usually a graft taken from the hamstring
or Achilles tendon from a host cadaver. An arthroscope allows a complete
evaluation of the entire knee joint, including the knee cap, the cartilage
surfaces, the meniscus, the ligaments, and the joint lining. Then, the new
ligament is attached to the bone of the thigh and lower leg with screws to hold
it in place. Surgery to repair the posterior cruciate ligament is
controversial due to its placement and technical difficulty.
It is possible for the PCL to heal on its own without surgery when it is in
Grades I and II. PCL injuries that are diagnosed in these categories can have
their recovery times reduced by performing certain rehabilitative
exercises. Fernandez and Pugh(2012) found that following a PCL grade II
diagnosis, a multimodal treatment that spanned over the course of 8 weeks
consisting of chiropractic lumbopelvic manipulation, physiotherapy, and
implementing an exercise program that emphasized in eccentric muscle
contraction which proved to be an effective way to recover from the PCL
injury. For Grades III and IV, operative surgery is recommended or is usually
needed. Grafts is the method when addressing PCL injuries that are in need
of operative surgery. With grafts, there are different methods such as the tibial
inlay or tunnel method. Other animals
In the quadruped stifle, based on its anatomical position, it is referred to
as the caudal cruciate ligament. Additional images
References External links
lljoints at The Anatomy Lesson by Wesley Norman
Dealing with Torn Ligament in the Knee http:www.orthspec.comPCL-injuries.pdf