Forces in the knee joint whilst rising from a seated position.

Knee joint forces were determined by kinesiological techniques, using a high speed cine camera, a force platform, a specially constructed dynamometerized chair, and EMG recorders; so that a comparison could be made for rising from a normal chair with and without the aid of arms, and for rising from high and low chairs. For rising from the seated position, the knee joint forces parallel to the long axis of the tibia at the point of contact between the tibia and femur were found to be up to seven times body weight at about the time when the body left contact with the chair. When rising from a chair with the aid of arms, the knee joint forces were reduced to less than three times body weight. Knee joint and muscle forces were also reduced when rising from a high seat compared with rising from a low seat.