McMurray's Test: Purpose, Procedure, Interpretation, and Limitations

What is the McMurray's Test Knee?

The McMurray's Test is a clinical orthopedic examination maneuver used by healthcare professionals to assess the integrity of the menisci within the knee joint, primarily to detect meniscal tears.

Understanding the Knee Meniscus

To fully appreciate the McMurray's Test, it's essential to understand the knee's anatomy. The knee joint is formed by the femur (thigh bone), tibia (shin bone), and patella (kneecap). Between the femur and tibia lie two C-shaped pieces of cartilage called menisci (plural for meniscus).

• Medial Meniscus: Located on the inner side of the knee.
• Lateral Meniscus: Located on the outer side of the knee.

These menisci act as crucial shock absorbers, distribute load across the joint, provide stability, and facilitate smooth movement by increasing the contact area between the bones. Due to their position and role in weight-bearing and rotation, they are highly susceptible to injury, particularly tears, which can result from twisting motions, direct impact, or degenerative changes over time.

Purpose of the McMurray's Test

The primary purpose of the McMurray's Test is to help clinicians diagnose tears in the medial or lateral meniscus. It is a provocative test, meaning it attempts to reproduce the symptoms (pain, clicking, catching) that a patient might experience if they have a meniscal injury. By applying specific stresses to the knee, the test aims to "trap" a torn piece of meniscus between the femur and tibia, thus eliciting a positive response. It is a fundamental component of a comprehensive orthopedic knee examination.

How the McMurray's Test is Performed

The McMurray's Test is typically performed with the patient lying on their back (supine position) and the examiner standing beside the affected knee. While there are slight variations, the general procedure involves specific movements designed to stress each meniscus individually.

General Procedure Steps:

1. Patient Positioning: The patient lies supine. The examiner holds the patient's heel with one hand and places the other hand on the knee joint line, specifically palpating the medial and lateral joint lines to feel for clicks or crepitus.
2. Full Flexion: The knee is brought into full flexion (bent as much as possible), and the hip is also flexed. This position helps to "load" the menisci.

Testing the Medial Meniscus:

• From the fully flexed position, the examiner applies a valgus stress (force directed inward, gapping the medial side of the knee) to the knee.
• Simultaneously, the examiner externally rotates the tibia (foot points outward).
• While maintaining the valgus stress and external rotation, the knee is slowly extended (straightened) to approximately 90 degrees of flexion. The examiner listens and feels for a click, clunk, or notes any pain.

Testing the Lateral Meniscus:

• From the fully flexed position, the examiner applies a varus stress (force directed outward, gapping the lateral side of the knee) to the knee.
• Simultaneously, the examiner internally rotates the tibia (foot points inward).
• While maintaining the varus stress and internal rotation, the knee is slowly extended (straightened) to approximately 90 degrees of flexion. The examiner listens and feels for a click, clunk, or notes any pain.

The rationale is that external rotation and valgus stress put compressive forces on the medial meniscus, while internal rotation and varus stress compress the lateral meniscus. The extension phase then attempts to "catch" a torn fragment.

Interpreting the Results

A "positive" McMurray's Test is indicated by one or more of the following during the maneuver:

• A palpable or audible click or clunk: This is often the most significant finding, suggesting that a torn meniscal fragment is being caught between the femoral condyle and tibial plateau.
• Reproduction of the patient's pain: If the test elicits the specific knee pain the patient has been experiencing.
• A feeling of "giving way" or apprehension: Though less common, this can also indicate instability due to a meniscal tear.

Specific Interpretations:

• A positive test with external rotation and valgus stress (medial meniscus test) suggests a medial meniscal tear.
• A positive test with internal rotation and varus stress (lateral meniscus test) suggests a lateral meniscal tear.

It's crucial to note the exact point in the range of motion where the click or pain occurs, as this can sometimes indicate the location of the tear (e.g., clicks earlier in extension might suggest a posterior tear).

Limitations and Considerations

While the McMurray's Test is a widely used and valuable clinical tool, it is not definitive on its own and has several limitations:

• Sensitivity and Specificity: The test's accuracy varies. It may produce false positives (positive test without a tear) or false negatives (tear present but test is negative). Its sensitivity (ability to correctly identify those with the condition) and specificity (ability to correctly identify those without the condition) are moderate, typically ranging from 50-70% for both.
• Subjectivity: The interpretation can be somewhat subjective, relying on the examiner's ability to feel subtle clicks and the patient's report of pain.
• Other Conditions: Other knee pathologies, such as degenerative joint disease or plica syndrome, can sometimes produce similar symptoms (e.g., clicking) and lead to a false positive.
• Need for Confirmation: A positive McMurray's Test typically warrants further investigation, such as Magnetic Resonance Imaging (MRI), to confirm the diagnosis and assess the severity and location of the tear.
• Examiner Skill: The test should be performed by a qualified healthcare professional (e.g., physician, physical therapist, athletic trainer) with a thorough understanding of knee anatomy and proper technique.

The McMurray's Test is best used as part of a comprehensive clinical evaluation, including a detailed patient history, observation, palpation, and other special tests, to form a complete diagnostic picture.

When to Seek Medical Attention

If you experience persistent knee pain, swelling, clicking, locking, or a feeling of your knee "giving way," especially after a specific injury or twisting motion, it is important to seek evaluation from a healthcare professional. They can perform a thorough examination, including tests like the McMurray's Test, and recommend appropriate diagnostic imaging and treatment strategies.