Gross anatomy means anatomy that you can see with your eyes, not needing to use a microscope to see the individual cells.
External inspection, Dissection, Imaging
Gross anatomy would include looking at the knee, and asking the life patient to move, perhaps while resisting certain movements to better understand the integrity of muscles, tendons and bones. More detailed anatomy could be understood during live surgery, or in the cadaver during dissecton. Imaging techniques such as X-ray, CT scan and MRI will give further information.