Collateral Ligament Pathology Workup

Updated: Apr 10, 2021
  • Author: Michael P Nogalski, MD; Chief Editor: Thomas M DeBerardino, MD  more...
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Imaging Studies

Radiography and a physical examination usually suffice for grade 1 collateral ligament injuries in which the diagnosis appears straightforward. With more pain, larger effusions, or if the diagnosis is unclear, magnetic resonance imaging (MRI) may be of value. A repeat examination 2 weeks after the injury may provide more accurate findings.

According to American College of Radiology (ACR) Appropriateness Criteria for imaging acute knee trauma, plain radiographs are usually appropriate for the initial evaluation. MRI without intravenous contrast is recommended as the most approriate follow-up study if no fracture is found. [25]

MRI is very sensitive and specific for medial collateral ligament (MCL) injuries; however, only a physical examination can quantitate or grade the injury. Meniscal, other ligamentous, patellofemoral, and possibly chondral injuries can be identified. [26]  Grade 3 MCL injuries may be associated with other concomitant injuries, and if suspicion exists, MRI is helpful in evaluation. 

In lateral collateral ligament injuries, plain radiographic findings may be normal or, in bony avulsions of the lateral collateral ligament (LCL), show a fibular head avulsion fracture. MRI is the optimal test to demonstrate the lateral structures. MRI can also be used to evaluate the other structures in the knee, such as the posterior cruciate ligament (PCL), anterior cruciate ligament (ACL), MCL, and menisci. [27]

For a more in-depth discussion, see Collateral Ligament Injury MRI.


Diagnostic Procedures

Examination under anesthesia has some value, especially in combined ligament injuries when evaluation of the knee would be painful and less accurate. Arthroscopy has little value in the evaluation of these specific injuries but does aid in the evaluation of associated ligamentous, chondral, and meniscal injuries.


Posterolateral Tests

In the posterolateral drawer test, the examiner supports the patient's foot and, with the knee first at 30 degrees and then at 90 degrees of flexion, places a posterolateral spin on the tibia by pushing laterally on the medial anterior tibia. Findings should ideally be compared with a normal opposite knee. The angle of the foot with respect to the midsagittal plane can be used to gauge the amount of spin that the tibia has with respect to each femur. If the posterolateral spin of the tibia is greatest at 30 degrees and minimal at 90 degrees, then a posterolateral complex injury is likely. If the posterolateral spin is larger at 90 degrees, then PCL injury associated with a lateral complex injury is likely.

In the external recurvatum test, both legs are raised off the examination table with the examiner grasping the great toe while the patient is supine. If the tibial tubercle rotates outward and the knee goes into recurvatum, laxity of the posterolateral corner is present. Comparison with the opposite lower extremity can help identify normal versus abnormal rotation and recurvatum.

The posterolateral spin test at 30 and 90 degrees uses the same principle as the posterolateral spin test above but uses the thigh-foot angle, as measured with an external rotation on the tibia exerted on the feet with the knees at 30 and 90 degrees. Having an assistant hold the knees together and performing this test with the patient supine is helpful. The patient is asked to place his or her knees at positions of 30 and 90 degrees as set by the examiner. With an assistant holding the knees together, the thigh-foot angle is assessed after exerting an external rotation force on both feet simultaneously. Side-to-side differences of greater than 10 degrees are thought to be significant. Significantly increased external rotation at 30 degrees indicates a posterolateral complex injury. If the spin is also increased at 90 degrees, then likely both the PCL and posterolateral complex are injured.