The McMurray test is a test for the integrity of the knee meniscus.
How to perform the McMurray test
The patient lies on his back with the knee bent to 90 degrees. The surgeon uses one hand on the knee to apply a valgus force (stressing the knee inwards) while the other hand grasps the patient's foot (sole) and rotates the lower limb externally (outwards). If a click is felt or heard or the patient experiences pain, then this is suggestive of a damaged meniscus.
McMurray's Test and Joint Line Tenderness for Medial Meniscus Tear: Are They Accurate? Gupta Y, Mahara D and Lamichhane A. Ethiop J Health Sci. 2016 Nov; 26(6): 567–572.