McMurray Test: Purpose, Performance, and Interpretation

The McMurray Test: Purpose and Application

The McMurray test is a clinical orthopedic examination maneuver primarily employed to assess for tears within the menisci (cartilage) of the knee joint, specifically the medial and lateral menisci.

Understanding the Knee Menisci

To fully grasp the purpose of the McMurray test, it's essential to understand the anatomy and function of the knee menisci. The knee joint, a complex hinge joint, contains two C-shaped pieces of fibrocartilage: the medial meniscus (on the inner side of the knee) and the lateral meniscus (on the outer side).

These menisci serve several critical functions:

• Shock Absorption: They act as cushions, absorbing impact and distributing forces across the knee joint.
• Joint Stability: They improve the congruence between the rounded femoral condyles and the relatively flat tibial plateau, enhancing joint stability.
• Load Distribution: They increase the contact area within the joint, reducing stress on the articular cartilage.
• Lubrication and Nutrition: They assist in the distribution of synovial fluid, contributing to joint health.

Due to their vital roles and anatomical position, the menisci are susceptible to injury, particularly during twisting movements, deep squatting, or direct impact, which can lead to tears.

The Primary Purpose: Detecting Meniscal Tears

The fundamental purpose of the McMurray test is to provoke symptoms associated with a meniscal tear, thereby helping a clinician identify its presence and often, its location (medial or lateral). It is a provocative test, meaning it attempts to reproduce the mechanism of injury or stress the injured tissue to elicit pain, clicking, or a catching sensation.

When a meniscus is torn, a fragment of the cartilage can become displaced or entrapped between the femur and tibia during specific movements. The McMurray test is designed to "trap" this torn fragment, causing:

• Pain: Localized pain along the joint line.
• A Palpable or Audible Click/Clunk: A distinct sensation or sound as the torn meniscus is caught and then released.
• Locking Sensation: In some cases, the knee may briefly "lock" due to the entrapped fragment.

How the Test is Performed (Overview)

The McMurray test is performed by a trained healthcare professional, such as a physician, physical therapist, or athletic trainer. It requires the patient to be in a supine (lying on their back) position while the examiner manipulates the patient's knee.

The general procedure involves:

• The examiner grasping the patient's heel with one hand and placing the other hand over the knee joint, specifically palpating the joint line.
• The knee is fully flexed.
• To test the medial meniscus, the examiner externally rotates the tibia while applying a valgus (outward) stress and slowly extends the knee. This maneuver attempts to pinch the posterior aspect of the medial meniscus.
• To test the lateral meniscus, the examiner internally rotates the tibia while applying a varus (inward) stress and slowly extends the knee. This maneuver attempts to pinch the posterior aspect of the lateral meniscus.

Throughout the extension phase, the examiner is listening and feeling for any clicks, clunks, or thuds, and observing for any patient-reported pain or apprehension.

Interpreting the Results

A positive McMurray test is indicated by:

• A palpable or audible click, clunk, or thud felt or heard by the examiner.
• Localized pain reported by the patient along the joint line corresponding to the meniscus being tested (e.g., medial joint line pain during medial meniscus maneuver).
• A catching or locking sensation in the knee.

The specific maneuver that elicits the positive finding can help the clinician determine whether the medial or lateral meniscus is more likely injured. For instance, a clunk with external rotation and valgus stress during extension points towards a medial meniscal tear.

Limitations and Clinical Context

While the McMurray test is a widely used and valuable clinical tool, it is important to understand its limitations:

• Not a Definitive Diagnosis: A positive McMurray test suggests a meniscal tear but is not conclusive on its own. It is part of a broader orthopedic examination.
• False Positives and Negatives: The test can produce false positives (positive test without a tear) or false negatives (tear present but test is negative), particularly in chronic tears or tears that are not easily caught.
• Operator Dependence: The accuracy of the test can vary depending on the skill and experience of the examiner.
• Need for Further Imaging: Often, if a meniscal tear is suspected based on the McMurray test and other clinical findings, an MRI (Magnetic Resonance Imaging) is ordered to confirm the diagnosis, determine the size and type of the tear, and rule out other knee pathologies.
• Other Knee Pathologies: Pain or clicking during the test can sometimes be attributed to other conditions, such as osteoarthritis, plica syndrome, or ligamentous instability, rather than solely a meniscal tear.

Clinical Significance and Next Steps

A positive McMurray test plays a crucial role in guiding the clinician's diagnostic process. If the test is positive and aligns with the patient's symptoms and history, it significantly increases the suspicion of a meniscal tear. This often prompts:

• Further diagnostic imaging, most commonly an MRI.
• Consideration of treatment options, which can range from conservative management (rest, ice, physical therapy, anti-inflammatory medication) for minor tears to surgical intervention (arthroscopy for repair or partial meniscectomy) for more significant or symptomatic tears.

Conclusion

The McMurray test is a cornerstone of the orthopedic knee examination, primarily serving as a provocative test to assess for meniscal tears. By applying specific stresses to the knee joint, it aims to reproduce the symptoms associated with a torn meniscus. While not a standalone diagnostic tool, its findings, when combined with a comprehensive patient history, physical examination, and potentially advanced imaging, provide invaluable information for diagnosing knee injuries and guiding appropriate management strategies. For anyone experiencing knee pain, especially after a twisting injury, consulting a healthcare professional for a thorough evaluation is always recommended.