When in a sitting position the hips and knees are flexed at 90 degrees and the bodys weight is borne by the pelvis, particularly the ischial tuberosities, which are bony protuberances of the lower portion of the ischium. Using a wheel chair results in prolonged sitting unless interventions are used to promote local circulation. (b) Pressure to the scapulae occurs in all back-lying positions, such as the supine and Fowlers positions. (c) Pressure to a trochanter occurs in a side-lying, not the sitting, position. (d) Pressure to the malleolus (medial and lateral) of the ankle occurs in a side-lying, not a sitting, position