Foot Weight-Bearing in Supported Standing: Influence of Verticalization Angles and Hip/Knee Flexion in Children and Adolescents with Cerebral Palsy (GMFCS IV-V)

Background: Supported standing is commonly prescribed for children and adolescents with cerebral palsy (CP) to support musculoskeletal health and participation. However, objective data on foot loading under different positioning conditions are limited, particularly in individuals with severe motor impairment (GMFCS IV–V). This study quantified foot weight-bearing during supported standing across combinations of verticalization angle and hip/knee flexion. Methods: Twenty-six children and adolescents with CP (GMFCS IV–V; 6–17 years) were assessed using a standardized back-supported standing system. Foot loading was measured with two calibrated force plates at six verticalization angles (0°, 30°, 45°, 60°, 75°, 90°) combined with four hip/knee flexion angles (0°, 15°, 30°, 45°). Loading was expressed as percentage of body weight (% BW). Effects were analyzed using repeated-measures analysis of variance. Results: Foot loading increased progressively with increasing verticalization angles across all hip/knee flexion conditions. Clinically relevant loading levels (>70% BW) were achieved at a verticalization angle of 60° in most flexion conditions. Maximum loading was observed at 90° verticalization combined with 30° hip/knee flexion (96.4% BW). At 90° verticalization, foot loading remained substantial even with 45° hip/knee flexion (81.4% BW). Increasing hip/knee flexion did not result in a linear reduction in foot loading; a significant decrease was observed only at 45° flexion. Conclusion: Verticalization angle is the primary determinant of foot loading during supported standing in children and adolescents with severe CP. Meaningful foot loading can be achieved at moderate verticalization angles despite hip and knee flexion, supporting flexible positioning strategies.