Factors associated with flexed knee gait in unilateral cerebral palsy

Purpose: A flexed knee gait is a common gait in children with unilateral cerebral palsy. In children without knee contracture, hamstring spasticity is commonly considered a major contributor to a flexed knee gait. We hypothesized that the popliteal angle would not correlate to a flexed knee gait. Methods: This retrospective study included 109 children with unilateral cerebral palsy who had undergone complete 3D gait analysis. Children who had previous surgery or knee flexion contracture were excluded. Children were divided into three groups based on knee position during stance as determined by 3D gait analysis: flexion (FK, 47), hyperextension (HK, 42), and normal (NK, 20). Results: There were no significant correlations between popliteal angle and dynamic peak knee extension in stance or at initial contact. Similarly, peak dorsiflexion during the stance phase did not correlate with dynamic peak knee extension in stance (all p > 0.05). Significant differences were observed in foot position during stance between FK and HK groups, as well as in quick stretch dorsiflexion with the knee extended between HK and NK groups. Conclusion: A flexed knee gait in children with unilateral cerebral palsy does not always correlate with the popliteal angle or dynamic ankle position in gait. These factors may contribute but are insufficient to explain all observed differences. A flexed knee gait likely involves a complex interplay of motor control, strength, spasticity, and lever arm dynamics, indicating that interventions at a single level may not fully improve dynamic knee extension.