Abstract
Background/Objectives: Guided growth changes frontal-plane gait mechanics in idiopathic genu valgum, but the durability of these adaptations through skeletal maturity remains uncertain. This study examined their long-term course. Methods: Seventeen participants (31 treated limbs) underwent three-dimensional gait analysis before plate insertion (t0), shortly before plate removal (t1), and after skeletal maturity (t2). Primary outcomes were the mean frontal knee angle during single support and the early- and late-stance peaks and stance mean of the internal frontal-plane knee moment. Longitudinal changes were assessed using linear mixed-effects models accounting for participant and limb dependence. Exploratory comparisons used laboratory reference data from 11 healthy participants. Results: Mean follow-up after plate removal was 59.66 ± 12.13 months. The mean frontal knee angle changed from −5.34° ± 2.61° at t0 to −0.08° ± 2.66° at t1 and −0.61° ± 2.27° at t2. The model-estimated change from t1 to t2 was −0.53° (95% confidence interval, −1.50° to 0.44°; Bonferroni-adjusted p = 0.798). All three knee-moment measures increased from t0 to t1, with no significant further changes to t2. These moments were below the laboratory reference values at t0 but above them at t1 and t2. Hip- and knee-rotation differences from the reference group persisted. Conclusions: Frontal-plane knee adaptations observed shortly before plate removal persisted, with small mean changes through skeletal maturity. Persistent kinetic and rotational differences suggest incomplete convergence toward the laboratory reference pattern. Further studies should examine the clinical relevance of these differences.