What is the key difference between passive and active orthotics in rehabilitation engineering?

• A. Passive orthotics require actuators; active orthotics do not.
• B. Passive orthotics provide structural support without actuators; active orthotics incorporate actuation or assistive elements requiring control software, power, and safety.
• C. Passive orthotics use electrical power; active orthotics are manual.
• D. Passive orthotics require sensors; active orthotics do not.

Answer: (B)

The main distinction is whether movement support comes from powered actuation. Passive orthotics provide structural support, alignment, and load distribution without any moving actuators or onboard power. They rely on their shape, materials, and fit to stabilize a joint or limit motion and do not require software control, power, or safety systems. Active orthotics, on the other hand, include actuators or other assistive elements that actively move or resist movement and require a control system, a power source, and safety considerations to manage that motion. For example, a nonpowered knee brace stabilizes the joint, while a powered ankle-foot orthosis uses a motor and control hardware to assist gait. The other statements misstate the role of power, actuation, or control in passive versus active devices.