Collateral Ligament Tear (Knee)

Preliminary Diagnosis: Medial Collateral Ligament (MCL) Tear (knee)

I. What imaging technique is first-line for this diagnosis?

MRI of the knee. There is no need for contrast.

II. Describe the advantages and disadvantages of this technique for diagnosing MCL tears (knee).

Advantages

• Diagnostic for MCL tears.

• Useful not only for diagnosis, but for categorization of the MCL tears according to severity (mild sprain, partial tears, complete tears, and detachments), location (proximal/middle/distal, superficial/deep), as well as for depicting chondral/osteochondral injuries, meniscal tears, ACL tears, and hemarthrosis.

• Does not include exposure to ionizing radiation.

Disadvantages

• Expensive.

• Time consuming.

• Requires patient cooperation, and the images are susceptible to motion artifact. Uncooperative patients may need sedation.

• Closed bore magnets may be uncomfortable for claustrophobic and obese patients.

III. What are the contraindications for the first-line imaging technique?

• Patients with non-MRI compatible implanted devices.

• MR imaging is also relatively contraindicated in pregnant women during the first trimester, due to a lack of research about the effect of the magnetic field on the embryo.

IV. What alternative imaging techniques are available?

• Computed tomography with intra-articular injection of contrast (CT-arthrography).

• Plain radiographs.

• Ultrasound (gray scale).

V. Describe the advantages and disadvantages of the alternative techniques for diagnosing MCL tears.

CT arthrography

Advantages

• Does not involve magnetic fields, and therefore is a suitable method for patients with metallic implants/devices.

• The contrast injected into the joint space extravasates into the adjacent medial soft tissues in acute MCL injuries.

• This technique might be diagnostic or require additional evaluation.

Disadvantages

• Exposure to ionizing radiation.

• Is considered an invasive procedure, including intra-articular injection of contrast media, with possible complications including chemical synovitis, infection, hemorrhage, and pain.

• Subacute or superficial MCL tears may not be depicted by this imaging method.

Plain radiographs

Advantages

• Readily available, fast, low-cost imaging technique.

• Chronic injuries may present with calcification or ossification of the MCL (Pellegrini-Stieda syndrome).

Disadvantages

• Routine radiographic abnormalities associated with acute MCL tears are not diagnostic.

• Exposure to ionizing radiation.

• Plain film imaging is limited for soft tissue evaluation, offering poor anatomic detail.

Ultrasound

Advantages

• Ultrasound may be diagnostic in high grade MCL tears.

• Safe, cost-effective, quick, readily available method.

Disadvantages

• Ultrasound imaging is less accurate for low grade/partial tears.

• Operator-dependent imaging technique.

VI. What are the contraindications for the alternative imaging techniques?

CT arthrography and radiographs

• Contraindicated in pregnant women, especially during the first and second trimesters.

• In patients with prior allergic reactions (e.g., itching, rash, angioedema of the throat, anaphylaxis) to iodinated intravenous contrast, one should consider the risks and benefits of CT arthrography. These patients should be pretreated with steroids and antihistamines for a minimum of 13 hours prior to imaging.

Plain radiographs

No significant contraindications. Some institutions may require consent for pregnant women.

Ultrasound

There are no contraindications for ultrasound.