Lateral collateral ligament (LCL) knee injuries are typically diagnosed by a sports medicine physician or other health care professional. A person should be prepared to answer questions, undergo a physical exam, and have medical imaging (such as an x-ray) performed.

Patient Interview

A person should be prepared to answer questions about his or her medical history and details surrounding the injury, such as:

  • How did the injury occur?
  • Where is the location of the pain?
  • Was there a “popping” sound at the time of the injury?
  • Has the knee been injured before?
  • Do you feel catching, locking, or buckling with movement?
  • Does the knee feel weak or unstable, especially when bearing weight?

In addition to a patient interview, the physician will perform a series of physical exams to help confirm the diagnosis.

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Physical Exam

During a physical exam a doctor will perform specific assessments used to test for LCL tears. In addition to these tests, a doctor will check for any signs of trauma, such as swelling, bruising, and lacerations around the knee area.

Varus (adduction) stress test
This test is performed with the person lying on his or her back on an exam table.

  • The examiner will place one hand on the ankle and the other under the knee for support.
  • The physician will move the knee side to side by moving the ankle.
  • The examiner will then bend the leg to about 30 degrees of flexion and repeat the side-to-side movement.

This test may be performed on the unaffected leg for comparison. If the knee joint shows a great deal of sideways movement towards the body, it suggests the LCL has been injured.

Additional tests may be performed in order to determine if other structures in the knee have been injured.

Doctors often suggest waiting until after the initial knee swelling has gone down to perform a physical exam, as swelling and pain can affect the accuracy of tests.

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Medical Imaging

While most LCL tears can be diagnosed without medical imaging, a doctor may order an x-ray or MRI to rule out other possible injuries and to determine the severity of an LCL tear.

  • X-ray. An x-ray shows bones and can help determine if there is a fracture. Abnormalities in the bones’ alignment can also provide clues for a diagnosis.
  • Magnetic resonance imaging (MRI). An MRI provides a detailed image of the soft tissue surrounding the knee joint, including the ligaments. An MRI is helpful in confirming a diagnosis and determining the severity of an LCL tear.
  • Ultrasound. An ultrasound uses high frequency sound waves to build a picture of the knee’s tissues. Ultrasound may be utilized in situations where an MRI is not recommended.

Once an accurate diagnosis has been made, a doctor and patient can discuss recommended treatment options.

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