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Essentials of Diagnosis
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Usually follows anterior trauma to the tibia, such as a dashboard injury from a motor vehicle accident
The knee may freely dislocate and reduce
One-third of multi-ligament injuries involving the PCL have neurovascular injuries
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General Considerations
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The PCL is the strongest ligament in the knee
PCL injuries usually represent significant trauma and are highly associated with multi-ligament injuries and knee dislocations
More than 70–90% of PCL injuries have associated injuries to the posterolateral corner, medial collateral ligament (MCL), and anterior cruciate ligament (ACL)
Neurovascular injuries occur in up to one-third of all knee dislocations or PCL injuries
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Ambulation is difficult in most patients with acute injuries
Patients with chronic PCL injuries
Can ambulate without gross instability
However, they may complain of subjective "looseness" and often report pain and dysfunction, especially with bending
Clinical examinations of PCL injuries include the "sag sign"
Patient is placed supine and both hips and knees are flexed to 90 degrees
Because of gravity, the knee with the PCL injury will have an obvious set-off at the anterior tibia that is "sagging" posteriorly
A PCL injury is sometimes mistaken for an ACL injury during the anterior drawer test, since the tibia is subluxed posteriorly in a sagged position and can be abnormally translated forward, yielding a false-positive test for an ACL injury
Pain, swelling, pallor, and numbness in the affected extremity may suggest a knee dislocation with possible injury to the popliteal artery
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Diagnostic Procedures
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