McMurray Test: Purpose, Performance, and Clinical Significance

What is the use of McMurray test?

The McMurray test is a clinical orthopedic maneuver used primarily to assess for meniscal tears within the knee joint, helping clinicians identify potential damage to the medial or lateral meniscus.

Introduction to the McMurray Test

The McMurray test is a foundational component of the orthopedic physical examination for the knee. Developed by Thomas P. McMurray, it is a provocative test designed to elicit symptoms indicative of a meniscal injury. For fitness professionals, understanding this test provides insight into common knee pathologies and the diagnostic process undertaken by healthcare providers for clients presenting with knee pain or dysfunction. While not definitive on its own, it serves as a crucial screening tool in the initial assessment of knee joint integrity.

Anatomy and Biomechanics: The Menisci

To appreciate the utility of the McMurray test, a brief review of knee anatomy, specifically the menisci, is essential. The knee joint, a modified hinge joint, is formed by the articulation of the femur (thigh bone), tibia (shin bone), and patella (kneecap).

• Menisci: These are two C-shaped, fibrocartilaginous structures located between the femoral condyles and the tibial plateau:
  • Medial Meniscus: Larger and more C-shaped, it is firmly attached to the medial collateral ligament (MCL) and the joint capsule, making it less mobile and thus more susceptible to injury.
  • Lateral Meniscus: Smaller and more O-shaped, it is less rigidly attached and more mobile, leading to a lower incidence of injury compared to the medial meniscus.
• Functions: The menisci play several critical roles in knee joint health and function:
  • Shock Absorption: Distribute compressive loads across the joint.
  • Joint Stability: Enhance congruity between the femoral and tibial surfaces.
  • Lubrication and Nutrition: Aid in the spread of synovial fluid.
  • Proprioception: Contribute to the body's sense of joint position.

Due to their critical load-bearing and stabilizing roles, the menisci are vulnerable to tears, particularly during movements involving twisting, pivoting, or deep squatting under load.

Purpose of the McMurray Test

The primary purpose of the McMurray test is to detect tears of the menisci. The test achieves this by attempting to trap a torn meniscal fragment between the femoral condyle and the tibial plateau, thereby reproducing the patient's pain, a "click," "pop," or "clunk" sensation.

• Differentiating Tears: The test can help differentiate between medial and lateral meniscal tears based on the specific maneuver performed and the location of the elicited symptoms.
• Provoking Symptoms: It is a provocative test, meaning it aims to provoke the symptoms (pain, mechanical sensation) that the patient experiences with their meniscal injury.

How the McMurray Test is Performed (Simplified Principle)

While the McMurray test is performed by trained healthcare professionals, understanding its mechanical principle is valuable. The test involves a series of controlled movements designed to load and stress specific parts of the menisci:

1. Patient Positioning: The patient lies supine (on their back) with the knee fully flexed.
2. Examiner's Maneuver: The examiner grasps the patient's foot and knee.
   • Medial Meniscus Assessment: The examiner applies a valgus stress (outward force to the knee) while externally rotating the tibia and slowly extending the knee. This maneuver stresses the medial meniscus.
   • Lateral Meniscus Assessment: The examiner applies a varus stress (inward force to the knee) while internally rotating the tibia and slowly extending the knee. This maneuver stresses the lateral meniscus.
3. Positive Test: A positive McMurray test is indicated by the reproduction of pain, a palpable or audible click, pop, or clunk as the knee is extended, especially if felt over the joint line. This sensation often signifies a torn meniscal fragment being caught between the femoral and tibial articular surfaces.

Interpreting the Results: What a Positive Test Means

A positive McMurray test suggests the likelihood of a meniscal tear.

• Pain and Mechanical Symptoms:
  • Pain: Localized pain over the medial joint line during the medial meniscus maneuver, or over the lateral joint line during the lateral meniscus maneuver.
  • Click/Pop/Clunk: An audible or palpable sensation, often described as a "clunk," is highly indicative of a meniscal tear, especially if accompanied by pain. This suggests a torn fragment is being caught.
• Specificity: While a positive test points towards a meniscal tear, it does not specify the exact type or severity of the tear (e.g., bucket-handle, radial, horizontal).

Clinical Significance and Limitations

The McMurray test is a valuable diagnostic tool but comes with important considerations:

• Clinical Screening Tool: It is best used as part of a comprehensive clinical examination, alongside patient history, other special tests (e.g., Apley's compression/distraction, Thessaly test), and palpation.
• Sensitivity and Specificity: The test's accuracy varies.
  • Sensitivity: It may not detect all tears (false negatives). Some tears, especially those that are chronic, stable, or small, may not produce a positive test.
  • Specificity: It can sometimes produce a positive result in the absence of a tear (false positives), particularly in knees with significant degenerative changes or other intra-articular pathologies.
• Complementary Imaging: A positive McMurray test often warrants further investigation with imaging studies, most commonly a Magnetic Resonance Imaging (MRI) scan, which provides detailed visualization of soft tissue structures like the menisci.
• Acute vs. Chronic Tears: The test may be more reliable in acute tears where the fragment is mobile and readily caught. Chronic tears or those with significant swelling may yield less clear results.

When is the McMurray Test Used?

The McMurray test is typically employed in the following scenarios:

• Initial Assessment of Knee Pain: When a patient presents with knee pain, particularly if they report symptoms like clicking, popping, catching, or locking.
• Following Acute Knee Trauma: Especially after twisting injuries, falls, or direct blows to the knee.
• Persistent Knee Symptoms: When non-specific knee pain persists and a meniscal injury is suspected based on the mechanism of injury or patient-reported symptoms.

Conclusion: The McMurray Test in Practice

The McMurray test remains a cornerstone in the orthopedic assessment of knee injuries. For fitness enthusiasts and professionals, understanding its purpose underscores the complexity of knee diagnostics and the importance of professional medical evaluation for persistent or acute knee pain. While a positive test strongly suggests a meniscal tear, it is never interpreted in isolation. Instead, it guides the clinical reasoning process, prompting further investigation and contributing to a holistic diagnosis and subsequent management plan, whether conservative rehabilitation or surgical intervention.