A three-part analysis was undertaken to increase understanding of the occurrence of pressure ulcers in lithotomy positions. An innovative measuring device was used to determine capillary pressure. Ankle blood pressure was measured compared to ankle height in 11 participants. Ankle systolic and diastolic pressure decreased approximately 20 mmHg per foot of elevation. Calf and heel capillary-support pressures were measured in 15 participants in the standard lithotomy position. Capillary-support pressure for the calf was substantially less than for the heel. Heel capillary-support pressures were measured in 16 participants in the high lithotomy position. As heel height increased, capillary-support pressure also increased.