The McMurray Test is a maneuver used during a physical examination of the knee to assess for potential injury. It is a fundamental part of the orthopedic assessment process, designed to reproduce symptoms associated with damage to the internal structures of the knee joint. This clinical evaluation is performed by trained clinicians to gather initial data regarding the source of a patient’s knee pain. The findings from this test guide the need for further diagnostic steps or imaging studies.
The Purpose of the McMurray Test
The test primarily evaluates the condition of the menisci, which are two C-shaped wedges of fibrocartilage within the knee joint. These structures sit between the thigh bone (femur) and the shin bone (tibia), enhancing joint stability and providing congruity between the bones. There is a medial meniscus on the inner side and a lateral meniscus on the outer side.
The menisci serve as shock absorbers, distributing the load across the joint surface during movement. Tears often occur when the knee is subjected to a sudden, twisting or rotational movement. The McMurray maneuver attempts to replicate this mechanical trapping of a torn meniscal fragment, which causes pain or a mechanical sensation if a tear is present.
Step-by-Step Procedure
The McMurray Test is performed with the patient lying supine on an examination table, allowing the leg to be relaxed. The clinician grasps the patient’s heel or ankle with one hand and places the other hand over the knee joint line. This stabilizing hand monitors for any mechanical responses, such as a “click” or “clunk.”
The test sequence begins with the knee and hip brought into maximal flexion. From this fully bent position, the examiner applies a specific rotational force to the lower leg while slowly extending the knee. The direction of rotation and the application of a collateral stress determine which meniscus is being evaluated.
Assessing the Medial Meniscus
To assess the medial meniscus, the examiner externally rotates the tibia and applies a valgus stress to the joint. Valgus stress involves gently pushing the knee inward while pulling the ankle outward, which opens the medial compartment of the knee slightly. While maintaining this external rotation and valgus stress, the examiner slowly extends the knee, moving it toward a straighter position.
Assessing the Lateral Meniscus
To evaluate the lateral meniscus, the examiner internally rotates the tibia and applies a varus stress. Varus stress involves gently pushing the knee outward while pulling the ankle inward, which opens the lateral compartment. The knee is then slowly extended from the flexed position while holding this internal rotation and varus force. The entire maneuver involves moving the knee from a position of full flexion to approximately 90 degrees of flexion or less, as this range is where a trapped meniscal fragment is most likely to be felt or heard.
Interpreting the Results
A positive result is indicated by the reproduction of the patient’s pain, a distinct palpable clunk, or an audible click during the extension phase of the maneuver. This mechanical response suggests that a portion of the torn meniscus is being caught or compressed between the femur and the tibia. The location and direction of the movement that triggers the response helps localize the potential tear.
Pain or a clunk that occurs during external rotation and extension suggests a tear in the medial meniscus. Conversely, a positive finding during internal rotation and extension points toward a tear in the lateral meniscus. Clinicians must distinguish between a painful clunk or catching sensation and a minor, painless click, as a small click may occur in a healthy knee.
Accuracy and Complementary Assessments
The McMurray Test is a useful clinical tool, but its accuracy varies significantly across studies. Reported sensitivity, which is the test’s ability to correctly identify a tear, has been cited in a wide range, sometimes as low as 16% or as high as 91%. The specificity, which is the test’s ability to correctly identify a knee without a tear, also shows considerable variation, often falling between 55% and 97%.
This variability means the test can produce false-positive or false-negative results, indicating that a single physical examination finding is not sufficient for a definitive diagnosis. The McMurray Test is typically performed alongside other clinical assessments, such as the Apley compression test or the Thessaly test, to improve diagnostic confidence. A combination of positive findings provides a stronger indication of injury.
For a conclusive diagnosis, diagnostic imaging is required, with Magnetic Resonance Imaging (MRI) being the preferred non-invasive method. MRI provides detailed images of the menisci and surrounding soft tissues. Arthroscopy, a minimally invasive surgical procedure, remains the standard for confirming the presence and extent of a meniscal tear.