The McMurray test is a common physical examination maneuver used by healthcare professionals to assess a patient’s knee, especially when a meniscal injury is suspected. This orthopedic assessment helps identify potential damage to the menisci, crucial cartilage structures within the knee joint. A “positive” result indicates that further investigation into the knee’s condition may be necessary.
The McMurray Test
The McMurray test is a manual clinical assessment performed by a healthcare provider to evaluate the menisci of the knee. During this procedure, the patient lies on their back while the examiner supports the leg, bending the knee to a full flexion. The examiner then places one hand over the knee joint to feel for any abnormal sensations and holds the patient’s foot with the other hand.
The test involves carefully rotating the lower leg internally and externally while slowly extending the knee. This maneuver applies controlled stress to the menisci, mimicking the kinds of movements that can cause meniscal tears. The healthcare provider observes for any sounds, sensations, or pain reported by the patient or felt during these movements, which can suggest a meniscal injury.
Interpreting a Positive Result
A positive McMurray test occurs when the maneuver elicits a distinct “click,” “pop,” “thud,” or pain within the knee joint. This audible or palpable event, often with discomfort, suggests a meniscal tear. The specific location of the pain or sound helps determine which meniscus, medial or lateral, might be affected.
The menisci are two C-shaped pieces of fibrocartilage that act as shock absorbers and stabilizers between the thighbone (femur) and the shinbone (tibia). They help distribute weight evenly across the knee joint and reduce friction during movement. When a meniscus is torn, a fragment of the cartilage can become pinched or caught between the bones during the rotational movements of the test, producing the characteristic click or pop. External rotation of the lower leg during extension typically stresses the medial meniscus, while internal rotation stresses the lateral meniscus, helping to pinpoint the tear.
Confirming the Diagnosis
A positive McMurray test is a strong clinical indicator but not a definitive diagnosis. It prompts further diagnostic steps. Magnetic Resonance Imaging (MRI) is commonly used to confirm the presence and extent of a meniscal tear.
An MRI provides detailed images of soft tissues within the knee, allowing precise visualization of the menisci, ligaments, and other structures. This imaging differentiates between various types of tears and identifies any associated knee injuries. If diagnosis remains uncertain or surgical intervention is considered, arthroscopy, a minimally invasive procedure, may be performed for diagnosis and treatment.
Test Limitations
While valuable as a screening tool, the McMurray test is not completely accurate in diagnosing meniscal tears. Its reliability varies, with reported sensitivity ranging from approximately 16% to 70% and specificity between 59% and 97%. This variability is influenced by factors including the examiner’s skill and the patient’s pain tolerance.
False positives, where the test is positive but no tear is present, and false negatives, where a tear exists despite a negative test result, can occur. These limitations mean that the McMurray test is best used as part of a comprehensive clinical examination, rather than as a standalone diagnostic method. Its utility lies in guiding the diagnostic process and indicating the need for more advanced imaging or procedures.