The relationship of the angle of immobilisation of the knee to the force applied to the extensor mechanism when partially weight-bearing. A gait-analysis study in normal volunteers.
We describe the influence of the angle of immobilisation during partial weight-bearing on the forces across the extensor mechanism of the knee. Gait analysis was performed on eight healthy male subjects with the right knee in an orthotic brace locked at 0 degree, 10 degrees, 20 degrees and 30 degrees, with the brace unlocked and also without a brace. The ground reaction force, the angle of the knee and the net external flexion movement about the knee were measured and the extensor mechanism force was calculated. The results showed a direct non-linear relationship between the angle of knee flexion and the extensor mechanism force. When a brace was applied, the lowest forces occurred when the brace was locked at 0 degree. At 30 degrees the forces approached the failure strength of some fixation devices. We recommend that for potentially unstable injuries of the extensor mechanism, when mobilising with partial weight-bearing, the knee should be flexed at no more than 10 degrees.
Khan
W S
WS
Department of Trauma and Orthopaedics, Stockport NHS Foundation Trust, Stockport SK2 7JE, UK. wasimkhan@doctors.org.uk
Jones
R K
RK
Nokes
L
L
Johnson
D S
DS
D000328:Adult; D001696:Biomechanical Phenomena; D005684:Gait / Q000502:physiology*; D006801:Humans; D007103:Immobilization / Q000502:physiology*; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D009141:Musculoskeletal System / Q000293:injuries*; D016474:Weight-Bearing