Laboratory Studies
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Laboratory studies usually are not indicated for the diagnosis of a medial collateral ligament (MCL) or lateral collateral ligament (LCL) injury.
Imaging Studies
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Plain films in patients with suspected knee ligamentous injuries should include anteroposterior, lateral, intercondylar notch, and sunrise views. Avulsion fractures are often noted in knee ligament injuries. Indications for plain knee radiographs in suspected knee ligamentous injuries (Pittsburgh decision rules) are blunt trauma or a fall with one of the following criterion:
The patient is unable to walk 4 weight-bearing steps.
The patient is older than 50 years or younger than 12 years.
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Magnetic resonance imaging (MRI) is helpful for ruling out other soft-tissue injuries (eg, anterior or posterior cruciate ligament tears, meniscus injury). MRI is very sensitive in detecting tears of the collateral ligaments. However, it is not reliable for differentiating grades of injury, and use of the modality can lead to underestimation of the degree of injury. [14, 15]
The MCL can usually be visualized in its entirety in the coronal plane. A partial tear of the MCL is seen on T2-weighted MRI scans as an area of increased signal intensity, representing edema. The ligament may irregular. A complete tear of the MCL is marked by edema at the rupture site and retraction of the free ends.
The LCL is best visualized on coronal images. It tends to be of low signal intensity and have uniform thickness. Partial tears are characterized by edema. A complete LCL tear may be associated with a small avulsion of the styloid process of the fibular head and with marked edema.
Procedures
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If an effusion is present, arthrocentesis of the knee may be indicated to rule out hemarthrosis.
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The medial and lateral collateral ligaments of the knee. Courtesy of Randale Sechrest, MD, CEO, Medical Multimedia Group.
