Muscle Strength in Children and Adolescents With Haemophilia on Prophylaxis: An Age‐Adjusted Dynamometric Study

INTRODUCTION: Children with haemophilia (CwH) may show reduced muscle strength due to recurrent haemarthroses and disuse. Despite prophylaxis, data on strength profiles in modern-treated paediatric populations are scarce. AIM: The purpose of the current study was to evaluate the influence of haemophilia on muscle strength in children and adolescents, adjusting for age. MATERIALS: Thirty-four boys with haemophilia (mean age = 12.0 years) on prophylaxis and 25 age-matched healthy male controls (mean age = 11.3 years) underwent isometric dynamometry of bilateral elbow and knee flexion/extension using a MicroFet2 device. Eight strength variables were analyzed via general linear model (GLM) with age as covariate and group as factor, followed by regression models. RESULTS: Strength correlated strongly with age (r = 0.68-0.87, p < 0.001). The GLM showed significant main effects of age (p < 0.001) and group (p = 0.006). Univariate tests revealed lower strength in CwH for left-knee flexion (p = 0.040) and extension (p = 0.007). Regression indicated an age-adjusted penalty of -17.9 N for left-knee flexion and -26.6 N for extension (p = 0.036 and 0.015, respectively). Differences narrowed with age. CONCLUSIONS: CwH display reduced isometric knee strength-particularly in the non-dominant limb-despite prophylaxis. Early, individualized physiotherapy and regular strength monitoring are recommended.