McMurray Test: Definition, Purpose, Procedure, and Interpretation

What is the definition of McMurray test?

The McMurray test is a clinical orthopedic examination maneuver used to assess the integrity of the menisci within the knee joint, specifically to detect tears or damage to the medial and lateral menisci.

Introduction to the McMurray Test

The McMurray test is a classic special test employed by healthcare professionals, including orthopedists, physical therapists, and sports medicine physicians, to aid in the diagnosis of meniscal injuries in the knee. Named after the British surgeon Thomas P. McMurray, this test involves specific movements of the knee joint designed to trap a potentially torn meniscus between the femoral condyles and the tibial plateau, thereby eliciting pain or a palpable/audible "click" or "clunk."

Anatomy Involved

To understand the McMurray test, it's crucial to briefly review the relevant anatomy of the knee. The knee is a complex hinge joint formed by the articulation of the femur (thigh bone), tibia (shin bone), and patella (kneecap). Between the femoral condyles and the tibial plateau lie two C-shaped cartilaginous structures known as the menisci:

• Medial Meniscus: Located on the inner side of the knee, it is larger and more firmly attached, making it more prone to injury.
• Lateral Meniscus: Located on the outer side, it is smaller and more mobile.

These menisci act as shock absorbers, distribute load across the joint, and contribute to knee stability. Tears in these structures can result from acute trauma (e.g., twisting injuries during sports) or degenerative changes over time.

Purpose of the Test

The primary purpose of the McMurray test is to clinically identify the presence of a meniscal tear. While imaging studies like Magnetic Resonance Imaging (MRI) are definitive, clinical tests like the McMurray test provide valuable immediate diagnostic information, guide further investigation, and help in formulating a preliminary treatment plan. It is particularly useful in differentiating meniscal injuries from other knee pathologies such as ligamentous sprains, patellofemoral pain, or osteoarthritis.

How the Test is Performed (Brief Overview)

The McMurray test is typically performed with the patient lying supine (on their back) on an examination table. The examiner stands at the patient's side, supporting the leg being tested.

• Patient Positioning: The patient lies supine with the knee fully flexed, and the examiner grasps the patient's heel with one hand and palpates the knee joint line with the other.
• Examiner Maneuver:
  • For Medial Meniscus Assessment: The examiner applies a valgus stress (force applied to the outer knee, pushing inwards) and externally rotates the tibia while slowly extending the knee. This maneuver attempts to trap the medial meniscus between the femur and tibia.
  • For Lateral Meniscus Assessment: The examiner applies a varus stress (force applied to the inner knee, pushing outwards) and internally rotates the tibia while slowly extending the knee. This maneuver attempts to trap the lateral meniscus.
• Observation: The examiner carefully observes for any pain elicited by the patient, and listens or feels for a "click" or "clunk" sensation along the joint line.

Interpreting the Results

The interpretation of the McMurray test is crucial for diagnosis:

• Positive Test: A positive McMurray test is indicated by a palpable or audible "click" or "clunk" sensation, often accompanied by pain, as the knee is extended during the maneuver.
  • A click or clunk during external rotation and valgus stress suggests a medial meniscal tear.
  • A click or clunk during internal rotation and varus stress suggests a lateral meniscal tear.
  • The location of the pain or click can help pinpoint the specific area of the tear (e.g., anterior, middle, or posterior horn).
• Negative Test: A negative test implies the absence of these specific signs, though it does not definitively rule out a meniscal injury, especially if the tear is small or non-displaced.

Limitations and Considerations

While a valuable clinical tool, the McMurray test has certain limitations:

• Sensitivity and Specificity: Like most orthopedic special tests, the McMurray test is not 100% accurate. Its sensitivity (ability to correctly identify those with the condition) and specificity (ability to correctly identify those without the condition) vary in research, meaning it can produce false positives or false negatives.
• Examiner Skill: The accuracy of the test is highly dependent on the skill and experience of the examiner.
• Patient Tolerance: Pain or guarding by the patient can sometimes make the test difficult to perform accurately.
• Other Knee Pathologies: Other conditions, such as articular cartilage damage or loose bodies within the joint, can sometimes produce similar symptoms (e.g., clicking), leading to potential misinterpretation.
• Clinical Picture: The McMurray test should always be used as part of a comprehensive clinical examination, integrating patient history, other physical findings, and potentially imaging studies for a definitive diagnosis.

Conclusion

The McMurray test serves as a fundamental clinical maneuver in the assessment of knee pain, specifically designed to identify potential meniscal tears. By applying specific stresses to the knee joint, it aims to reproduce the symptoms associated with a meniscal injury, providing valuable information to guide diagnosis and subsequent management. However, its results must always be interpreted within the broader context of a complete patient evaluation to ensure an accurate and effective treatment strategy.