Effect of Knee Flexion Contracture on Sagittal Alignment in Patients with Cerebral Palsy

Abstract

Background. Knee flexion contracture (KFC) is one of the most common secondary orthopedic complications in patients with cerebral palsy (CP), with a reported prevalence of up to 50%. It is primarily caused by muscle spasticity and imbalance between knee flexors and extensors, resulting in impaired knee extension and development of crouch gait. This gait pattern is associated with increased energy expenditure and reduced capacity for independent ambulation. KFC induces compensatory changes in proximal segments of the musculoskeletal system, including the pelvis and spine. Despite the evident biomechanical interrelationship, age-related mechanisms of adaptation of sagittal spinopelvic alignment remain insufficiently understood.Aim. To evaluate the impact of knee flexion contracture on sagittal spinopelvic parameters in children with cerebral palsy.Materials and Methods. This study included 89 children with CP and KFC aged 4–17 years, classified as Gross Motor Function Classification System (GMFCS) levels II–III. Patients were divided into two age groups: Group 1 (12 years, n = 34) and Group 2 (≥12 years, n = 55). The age threshold of 12 years was selected based on literature indicating completion of active lower limb growth and associated changes in sagittal gait patterns in CP. All patients underwent clinical examination and standing full-spine radiography. Sagittal parameters assessed included pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), thoracic kyphosis (TK), and sagittal vertical axis (SVA).Results and Discussion. In patients younger than 12 years, no statistically significant correlations were found between KFC severity and sagittal spinopelvic parameters, suggesting predominantly local compensation. In contrast, patients aged ≥12 years demonstrated systemic compensatory adaptations with two distinct patterns. The spinal pattern was characterized by decreased lumbar lordosis and anterior displacement of the sagittal vertical axis. The pelvic pattern involved pelvic retroversion and alterations in the mechanical axis of the lower limb, indicating progressive involvement of the musculoskeletal kinematic chain.Conclusion. Three sequential levels of compensation were identified: local, spinal, and pelvic. Spinopelvic changes in patients with cerebral palsy and knee flexion contracture reflect progressive adaptation of the musculoskeletal system.