Otto Bock Genium Patient Information page 9

Stairs and Obstacles function
Negotiating stairs step-over-step:
Although the 3B1/ 3B1=ST is a passive knee joint, which means it cannot actively initiate movements,
negotiating stairs step-over-step is possible.
In order to do so, the prosthetic foot has to be placed on the next higher step first with the knee flexed.
Then the hip is extended, which also extends the knee. This requires a sufficiently secure hold in the
socket and a certain level of residual limb strength. During physiological stair climbing, knee flexion is
accomplished by actively raising the lower part of the leg. With 3B1/3B1=ST knee joint, knee flexion
can be achieved via the mass inertia of the lower part of the leg. Immediately after lifting the extended
leg off the floor, simultaneously extend the hip briefly and then abruptly flex it. This whip action flexes
the knee. The 3B1/3B1=ST knee joint recognises this movement sequence and sets flexion resistance
to minimum. Without activation of this mode - i.e. with stance phase resistance - knee flexion would be
limited and unpleasant pressure would be felt on the residual limb. The movement pattern is very similar
to the physiological process if the toes extend below the next higher step at the beginning of the cycle.
Here, too, the heel has to be pulled back first. Practice the "toes under the step" movement pattern with
the sound side and with the prosthesis; then the complete movement pattern is intuitive and easy to learn.
When sufficient knee flexion has been achieved, the 3B1/3B1=ST Knee Joint increases extension resist-
ance so that there is enough time to position the foot on the next step before the knee joint is extended
again. The supporting area for the foot on the step has to be sufficient so that the heel does not extend
back too far over the edge. With too little support area, the lower leg would extend too early and position
the leg too far backwards. In this phase, the 3B1/3B1=ST Knee Joint has already maximised the flexion
resistance (that is, further flexion is blocked). The knee joint can no longer be flexed but only extended.
This ensures that the leg does not buckle if the hip strength is not sufficient for the extending motion.
Support yourself with your hand on the contralateral side. A smooth wall is also sufficient for this purpose.
This lateral support is intended to prevent the residual limb from twisting in the socket. Twisting can lead to
unpleasant surface tension between the skin and the socket. Lateral support also improves your balance.
When the knee joint is fully extended, the initial position has been reached. You can climb the next step
or continue walking normally.
Crossing obstacles:
The stairs and obstacles function can be used to cross obstacles. Instead of achieving the required
ground clearance of the prosthetic foot through lateral abduction of the extended leg, the whip action
described above can be used. This is also possible from the walking motion.
Take the weight off the prosthetic leg when the knee joint is extended and then perform the whip motion,
which switches the 3B1/3B1=ST Knee Joint to the stair and obstacle function. This delays the extension
movement, giving enough time and ground clearance to step over an obstacle.
Genium - Bionic Prosthetic System Ottobock | 33