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03-07-2011 | Podiatry | Article

Ankle and knee restriction impair driving ability


Free abstract

MedWire News: Below-knee plaster casts and knee braces on the right leg significantly impair a vehicle driver's ability to brake and perform an emergency stop, warn UK researchers.

"We suggest changes to the legislation to prevent patients from driving with lower-limb plaster casts or knee braces," recommend Andew Waton (Sunderland Royal Hospital) and colleagues in the British edition of the Journal of Bone and Joint Surgery.

The team used a driving simulator to examine braking performance in 23 healthy individuals wearing an above-knee plaster cast, a below-knee plaster cast, or a knee brace with increasing range of restriction on the right leg.

Specifically, the team measured "total brake reaction time" in the participants. This was comprised of "thinking time" (time between lead car braking and participant releasing the accelerator), "movement time" (time between accelerator release and onset of braking), and "brake travel time" (time from onset of braking to 100 N force on brake).

Overall total brake reaction time was significantly longer when the participants wore an above- or below-knee plaster cast or a knee brace fixed at 0°, compared with driving without right leg restrictions.

Further analysis revealed that the increase in total brake reaction time was due to significant increases in thinking time, movement time, and brake travel time with right leg restriction compared with no restriction.

"The increase in total brake reaction times for 0° brace, below-knee and above-knee plaster casts equates to a vehicle travelling an additional 1.4 m, 1.9 m and 2.8 m while stopping from 30 mph [48.3 km/h], respectively," report Waton et al.

They add that their study required drivers only to fully press the brake pedal and did not require fine adjustments to the brake that are commonly required while driving. In addition, total brake reaction time may be shorter than in real life due to the driver's expectation of the lead car's braking.

The team therefore concludes: "Our findings suggest that the legislation governing fitness to drive in the presence of lower-limb immobilization needs to be reconsidered."

MedWire ( is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2011

By Lynda Williams

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