Doctor, when can I drive? - Range of motion of the knee while driving a car.

Background: One of the most important activities of daily living is operating a motor vehicle. With increasing age the prevalence of musculoskeletal disorders such as knee osteoarthritis may interfere with an individual's ability to do so safely. Physicians are tasked with determining a patient's ability to drive and yet the necessary joint range of motion required for driving a car has not been characterized.

Methods: The range of motion of the right and left knees was recorded using electrogoniometers in 20 healthy subjects while driving a car on three route types (a) city streets, b) country roads and c) highways). Special emphasis was placed on the left knee associated with changing a gear.

Results: The range of motion while driving is 40-80° for the right and 20-85° flexion for the left knee. A significant difference was noted for each side (p < 0.01) with a higher flexion occurring in the left knee (p < 0.01). The average position of the knee while changing a gear (beginning, maximum, ending) was: right: 55°±10°, 62°±10°, 53°±10°; left: 67°±7°, 39°±8°, 66°±8° (mean flexion±standard deviation).

Conclusion: This study characterized the knee range of motion that occurs while driving a car. Our data suggests that common driving activities such as accelerating a vehicle or braking can be achieved with the right knee through a limited range of motion. The greater range of motion and the higher flexion of the left knee are mainly attributed to the gear changing. The present data may benefit physicians in their evaluation of driving capability.