[Anatomic conditions of sitting positions]

Sitting positions are anatomically defined. Three types are described: sitting on a chair, on the ground, and half-sitting position. The ischial support is always predominant in durable sitting; the others are subsidiary: trochanter, thigh, trunk or forelimb. The respect of the articular mobility of the hips and knees is important. Several orthopaedical and neurological diseases disturb the anatomical conditions of normal sitting.