Murray Test: Understanding, Interpretation, and Clinical Significance

What is a positive Murray test?

A positive Murray test is an orthopedic special test result indicating potential damage to the menisci of the knee, most commonly a meniscal tear, characterized by a palpable or audible click, snap, or pain during the maneuver.

Understanding the Murray Test

The Murray test is a clinical orthopedic assessment used by healthcare professionals, including physical therapists, sports medicine physicians, and kinesiologists, to evaluate the integrity of the knee's menisci. It is one of several provocative tests designed to elicit symptoms (pain, clicking, or locking) associated with meniscal pathology. While similar in principle to the more widely known McMurray test, the Murray test often emphasizes a specific dynamic movement pattern to stress the menisci.

Purpose of the Test:

• To identify the presence of a meniscal tear, particularly those involving the posterior horn or body of the meniscus.
• To differentiate meniscal injuries from other knee pathologies.

How the Test is Performed (General Description): The patient typically lies supine (on their back) with the examiner supporting the affected leg. The examiner flexes the patient's knee fully, then applies a combination of axial compression, rotation (internal and external), and varus/valgus stress while slowly extending the knee. The specific nuances of the Murray test often involve applying a particular rotational or stress component during extension to "trap" or impinge the damaged meniscal tissue.

Interpreting a Positive Murray Test

A positive Murray test result is observed when the maneuver reproduces the patient's knee pain, or when a distinct palpable or audible "click," "clunk," or "snap" is felt or heard within the knee joint during the movement.

Specific Indications of a Positive Result:

• Pain: Localized pain, especially along the joint line, strongly suggests meniscal irritation or tear. The location of pain (medial or lateral joint line) helps indicate which meniscus is involved.
• Clicking/Clunking/Snapping: An audible or palpable mechanical sound, often accompanied by a sensation of the knee "giving way" or "catching," is highly indicative of a meniscal tear, where a torn fragment of cartilage is being trapped or displaced within the joint.
• Limited Motion: In some cases, a torn meniscus can mechanically block full extension or flexion, which might be exacerbated by the test.

Medial vs. Lateral Meniscus Involvement: The specific direction of rotation and applied stress during the test helps differentiate between medial and lateral meniscal involvement:

• Medial Meniscus: Often implicated with external rotation and valgus stress during extension.
• Lateral Meniscus: Often implicated with internal rotation and varus stress during extension.

Clinical Significance and Further Steps

A positive Murray test is a significant finding in a clinical assessment, but it is rarely used in isolation. It serves as an important piece of the diagnostic puzzle, complementing information gathered from the patient's history, symptom presentation, and other physical examination findings.

Limitations and Considerations:

• Sensitivity and Specificity: Like most orthopedic special tests, the Murray test is not 100% accurate. It has varying degrees of sensitivity (ability to correctly identify those with the condition) and specificity (ability to correctly identify those without the condition). False positives (positive test without a tear) and false negatives (negative test with a tear) can occur.
• Other Conditions: Other knee pathologies, such as osteochondral defects, loose bodies, or patellofemoral pain syndrome, can sometimes produce similar symptoms or mimic a positive meniscal test.
• Patient Cooperation: The test requires the patient to be relaxed and able to tolerate some discomfort for accurate assessment.

Next Steps After a Positive Result: If a Murray test is positive and clinical suspicion for a meniscal tear remains high, the following steps are typically considered:

• Further Imaging: Magnetic Resonance Imaging (MRI) is often the gold standard for confirming meniscal tears, providing detailed images of soft tissues.
• Consultation with a Specialist: Referral to an orthopedic surgeon or sports medicine physician for definitive diagnosis and discussion of treatment options (conservative management, physical therapy, or surgical intervention like arthroscopy).
• Comprehensive Assessment: The positive test guides the clinician in performing a more targeted assessment of the knee, including palpation, range of motion, and stability tests.

Anatomy and Biomechanics Behind the Test

Understanding the anatomy and biomechanics of the knee is crucial to appreciating how the Murray test works. The knee joint is a complex hinge joint formed by the femur (thigh bone), tibia (shin bone), and patella (kneecap).

The Menisci: The menisci are two C-shaped, fibrocartilaginous discs located between the femoral condyles and the tibial plateau.

• Medial Meniscus: Larger, more C-shaped, and less mobile, making it more susceptible to injury.
• Lateral Meniscus: Smaller, more O-shaped, and more mobile. Their primary functions include:
• Shock Absorption: Distributing compressive loads across the joint.
• Joint Stability: Deepening the tibial plateau to enhance congruity with the femoral condyles.
• Lubrication and Nutrition: Aiding in the spread of synovial fluid.

Biomechanics of the Test: The Murray test is designed to exploit the biomechanics of the knee by applying specific forces that "trap" or "pinch" a torn meniscal fragment between the femur and tibia. As the knee moves from flexion to extension with applied rotation and varus/valgus stress, a torn meniscus can be forced into a position where it is impinged, leading to pain or a mechanical click. This mechanism mimics the forces that might cause pain or catching during daily activities or sports.

Differential Diagnosis and Related Tests

When evaluating for meniscal pathology, clinicians consider a range of possibilities and often employ a battery of tests to narrow down the diagnosis.

Other Common Meniscal Tests:

• McMurray Test: Similar to the Murray test, involving flexion, rotation, and extension with varus/valgus stress to elicit a click or pain.
• Apley's Compression and Distraction Test: Assesses meniscal integrity (compression) versus ligamentous injury (distraction) by rotating the tibia on the femur.
• Thessaly Test: A weight-bearing test where the patient rotates their body on the flexed knee.

Conditions that May Mimic Meniscal Pain:

• Ligamentous Injuries: ACL, PCL, MCL, LCL sprains can cause pain and instability.
• Osteoarthritis: Degenerative changes in the articular cartilage can cause joint line pain and crepitus.
• Patellofemoral Pain Syndrome: Pain around or behind the kneecap.
• Plica Syndrome: Irritation of a synovial fold within the knee.
• Loose Bodies: Fragments of cartilage or bone floating in the joint space.

Conclusion

A positive Murray test is a valuable clinical indicator that suggests the presence of a meniscal tear in the knee. While not definitive on its own, it provides crucial information when combined with a thorough patient history, physical examination, and, if necessary, advanced imaging like MRI. For fitness enthusiasts, personal trainers, and student kinesiologists, understanding the significance of such orthopedic special tests is vital for recognizing potential injuries, guiding appropriate referral, and ultimately facilitating effective rehabilitation and return to activity. Always consult with a qualified healthcare professional for accurate diagnosis and personalized treatment plans for knee pain or suspected injuries.