The McMurray’s test is a clinical orthopedic examination technique used by healthcare providers to assess for internal injuries within the knee joint. This physical maneuver is designed to help diagnose a tear in the menisci, which are the C-shaped cartilage pads in the knee. The test provides a non-invasive way to check for meniscal pathology when a patient presents with pain, clicking, or catching in the knee.
The Target Structure: Understanding the Meniscus
The knee joint contains two crescent-shaped pads of fibrocartilage known as the menisci, which sit between the thigh bone (femur) and the shin bone (tibia). These structures are referred to as the lateral meniscus (outside) and the medial meniscus (inner side). The primary function of the menisci is to act as shock absorbers, dispersing the load across the joint’s surface to reduce stress on the bone ends.
The menisci also contribute to the stability of the knee and help distribute lubricating fluid. The medial meniscus is a wider C-shape and is less mobile because it is firmly attached to the joint capsule and the medial collateral ligament, making it more susceptible to injury. Conversely, the lateral meniscus is a tighter, more closed circle and is slightly more mobile, which offers it a degree of protection.
Performing the McMurray’s Test
The McMurray’s test is designed to intentionally trap a potentially torn piece of the meniscus between the femur and the tibia. The patient is positioned on their back, and the clinician begins by flexing the patient’s knee fully toward the hip. The examiner places one hand over the knee joint to feel for abnormal sensations and uses the other hand to grasp the patient’s heel.
Testing the Lateral Meniscus
To target the lateral meniscus, the clinician internally rotates the tibia by turning the foot inward while applying a slight outward force, known as a varus stress, to the knee. The knee is then slowly extended from its fully bent position to about 90 degrees of flexion.
Testing the Medial Meniscus
The maneuver is repeated with external rotation of the tibia and a valgus stress (an inward force) applied to the knee to test the medial meniscus. These rotational and stress movements roll the femur over the menisci, stressing the cartilage.
Interpreting the Results and Next Steps
A “positive” McMurray’s test occurs when the maneuver reproduces the patient’s symptoms, such as an audible click, a palpable thud, or sharp, localized pain along the joint line. This positive sign suggests that a torn fragment of the meniscus is being caught and compressed. The location of the pain or click helps the clinician differentiate which meniscus is involved.
A positive result during external rotation and valgus stress indicates a likely tear in the medial meniscus, while a positive result during internal rotation and varus stress suggests a tear in the lateral meniscus. The McMurray’s test is a clinical indicator, not a definitive diagnosis, as other conditions like a loose piece of cartilage or osteoarthritis can sometimes cause similar symptoms. Research indicates the test has a high specificity, meaning a positive result is a strong sign of a tear, though its sensitivity is lower, meaning a tear can still exist even with a negative result.
Confirmation Imaging
Due to the test’s limitations, a positive McMurray’s test typically warrants follow-up imaging to confirm the diagnosis and plan treatment. Magnetic Resonance Imaging (MRI) is the preferred method, as it provides detailed images of the soft tissues, allowing for confirmation of the tear’s size and location.
Diagnostic Arthroscopy
In some cases, a surgeon may require a diagnostic arthroscopy. This is a minimally invasive procedure using a small camera to definitively visualize the tear before deciding on the appropriate course of action, whether it be surgical repair or non-operative management.