The McMurray test is a physical examination maneuver used by healthcare professionals to evaluate the knee joint. It serves as a preliminary screening tool when a patient has symptoms like pain, swelling, or a feeling of the knee “giving way.” The test assesses for potential internal damage by applying mechanical stress designed to provoke symptoms associated with injury, helping to guide the initial diagnostic process.
The Meniscus: Anatomy and Function
The knee joint contains two crescent-shaped pads of fibrocartilage, known as the menisci, located between the thigh bone (femur) and the shin bone (tibia). These structures are divided into the medial meniscus (inner side) and the lateral meniscus (outer side). Composed of tough tissue, the menisci distribute the load across the joint and act as the knee’s primary shock absorbers.
They significantly increase the contact area between the femur and tibia, which helps to reduce the pressure placed on the underlying articular cartilage. The menisci also contribute to joint stability and aid in lubrication, allowing for smooth movement. Because the medial meniscus is more firmly attached to the joint capsule, it is less mobile than the lateral meniscus, making it generally more prone to traumatic tears.
Step-by-Step: How the McMurray Test is Performed
The McMurray test is performed with the patient lying face up while the clinician manipulates the injured leg. The test begins with the knee fully flexed, allowing the examiner to grasp the patient’s heel with one hand and stabilize the knee joint with the other. The core mechanism of the test involves applying specific rotational and compressive forces while the knee moves from a bent to a straighter position.
To assess the medial meniscus, the clinician externally rotates the lower leg and then slowly moves the knee toward extension. Conversely, to check the lateral meniscus, the clinician internally rotates the lower leg while extending the knee. The purpose of this movement is to use the femur to “trap” or pinch a potentially torn fragment of the C-shaped cartilage against the tibia. This deliberate maneuver replicates the type of stress that causes symptoms in daily life, providing a physical indicator of meniscal pathology.
Understanding a Positive Result and Next Steps
A positive McMurray test occurs when the patient reports pain, or the clinician feels or hears a distinct clicking, popping, or snapping sensation along the joint line during the maneuver. This mechanical symptom strongly suggests that a torn piece of the meniscus is being caught between the femur and tibia as the knee is extended. While a positive result indicates a high likelihood of a meniscal tear, it is not a definitive diagnosis on its own.
The McMurray test is a screening tool, and its diagnostic accuracy can vary. Due to this variability, a positive result typically leads to the next step in the diagnostic process, which often involves medical imaging. X-rays may be taken to rule out bone-related issues like fractures or arthritis, but they cannot visualize the cartilage itself.
Magnetic Resonance Imaging (MRI) is the preferred method for confirming a meniscal tear, as it provides detailed images of the soft tissues within the knee. If the diagnosis is confirmed, treatment depends on the tear’s size, location, and the patient’s symptoms. Non-surgical management, including rest, ice, compression, elevation (RICE), and physical therapy, is often attempted first. For tears that cause persistent mechanical symptoms, like locking or catching, or those that fail to heal, arthroscopic surgery—a minimally invasive procedure—may be recommended to repair or trim the damaged meniscal tissue.