Page 71 - Handbook of Biomechatronics

66 Jeff Christenson

By aligning the axis of rotation of the goniometer with the central axis of the
joint and each leg along the joint segments in question, visual inspection of the
indicators will show the angle.
To understand what range of motion (ROM) Jacob currently achieves
with his sound-side knee and with his current prosthetic knee, you use a
goniometer. To do so, you align the central axis of the goniometer with
the axis of the knee being measured and take measurements at the extremes
of the ROM of both knees.

2.4 Lever
A lever (Fig. 6) is a device which consists of a beam with a fulcrum, or pivot
point (https://en.oxforddictionaries.com/definition/lever, Accessed 21
August 2017). Levers are used to sense force at one end of the beam and
transfer that force to the other end. By varying the fulcrum position along
the beam, the force can be amplified or reduced, based on the sum of torques
about the fulcrum.
A prosthetic foot is essentially a lever. Through heel strike to toe off,
forces are generated in the foot which are transferred to the knee through
the fulcrum of the ankle. You analyze Jacob’s ankle and find the heel strike
and toe-off forces.

2.5 Cable
A cable (Fig. 7) is a device which is able to sense a signal (force, torque, posi-
tion, etc.) at one end and transfer that signal to the other end (https://www.
merriam-webster.com/dictionary/cable, Accessed 21 August 2017). Cables
can be routed through devices and can modulate the signal strength through
the use of pulleys. Standard cable materials are steel or spectra cable.

Fig. 6 Schematic representation of a lever.