To perform Gaenslen's test, the hip joint is flexed maximally on one side and the opposite hip joint is extended, stressing both sacroiliac joints simultaneously. This is often done by having the patient lying on his or her back, lifting the knee to push towards the patient's chest while the other leg is allowed to fall over the side of an examination table, and is pushed toward the floor, flexing both sacroiliac joints. The test can also be performed with the patient in the lateral recumbent position.