Base of Support

The base of support (BOS) refers to the area beneath an object or person that includes every point of contact that the object or person makes with the supporting surface. These points of contact may be body parts e.g. feet or hands, or they may include things like crutches or the chair a person is sitting in.

The BOS is an important concept to understand when trying to determine a patient's ability to balance. The line of gravity, passing through the centre of gravity must fall within the BOS in order for the patient to stay balanced.