Arthrometric testing of the knee may also be done. In this test, your doctor will use an instrument to measure the looseness of your knee. This test is especially useful in people whose pain or physical size makes a physical exam difficult. An arthrometer has two sensor pads and a pressure handle that allows your doctor to put force on the knee. The instrument is strapped on to your lower leg so that the sensor pads are placed on the knee cap and the small bump just below it (tibial tubercle). Your doctor then measures pressure by pulling or pushing on the pressure handle.