Abstract
Aim
To determine the tensile forces across the knee extensor mechanism during walking, in simulated conditions of treatment.
Methods
Gait analysis of six normal subjects was performed, with full weight bearing unilateral immobilisation of the knee during walking. Measurements were taken without then with a brace, unlocked then locked at 0°, 0-10°, 0-20° and 0-30° of flexion. Mean and maximum knee flexion angles were measured, followed by calculation of the mean and maximum forces across the extensor mechanism during loading, supporting and propulsion phases of gait.
Results
The knee brace flexion angles set were consistently different to those measured kinematically, although the brace did act appropriately to restrict flexion. The highest flexion angles were found during the propulsion phase of gait. The calculated force through the extensor mechanism was greatest during the loading phase. The highest force recorded was with the brace locked between 0-10° of flexion, which in a 70kg person would be equivalent to a mean load of 343 N with a peak of 890 N.
Discussion
The maximum forces for all conditions measured in our study exceed those published in the literature for failure strength of many common fixation devices. We recommend that full weight bearing during walking should be avoided in the injured limb, after the initial repair of the knee extensor mechanism.
