Walking with an induced unilateral knee extension restriction affects lower but not upper body biomechanics in healthy adults

Abstract

BackgroundUnilateral knee flexion contractures (KFC) are frequently seen in orthopedic rehabilitation and often interfere with the normal gait pattern, resulting in passive and/or active secondary deviations. In order to prevent KFC-related complications such as patellofemoral pain or the knee spine syndrome, a comprehensive understanding of such deviations is necessary. Research questionHow does an artificially induced unilateral KFC affect whole body biomechanics in young healthy adults during gait? MethodsTwenty-four healthy young adults (females/males: 13/11; mean age: 27.3 ± 3.8 years) were included in this cross-sectional study. Using an 8-camera optical motion capture system and two embedded force plates, three-dimensional lower extremity, pelvis and trunk kinematics as well as lower extremity joint moments were derived during normal walking and walking with unilateral KFCs by means of a lightweight knee brace locked at 30° and 60° of flexion. Data were analyzed using one-dimensional statistical parametric mapping, allowing explorative group comparisons of continuous data rather than pre-defined discrete parameters. ResultsOn the braced side, increased hip flexion (p < 0.001, 1–100 % of gait cycle [%GC]), knee flexion (p < 0.001, 1–72 and 82–100 %GC) and ankle dorsiflexion angles (p < 0.001, 1–100 %GC) as well as external knee flexion moments (p < 0.001, 1–98 % of stance phase [%StPh]) and decreased ankle dorsiflexion (p < 0.001, 74–94 %StPh), hip flexion and hip adduction moments (p < 0.001, 1–32 %StPh and p < 0.001, 71–92 %StPh, respectively) were observed. The unbraced side showed similar but less pronounced deviations. Pelvis and upper body kinematics were not altered, suggesting that the lower limbs fully compensate for KFCs of less than 30°. SignificanceAsymmetric limb loading and considerable increases in external knee flexion moments might increase the risk for adverse effects of lower extremity joints in the long-term. It seems therefore important to treat KFCs as early as possible and to implement preventive strategies to avoid possible complications.