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    Jennifer Lee Hicks.
    Many children with cerebral palsy walk with excessive knee flexion, an inefficient locomotion pattern known as crouch gait that progressively worsens over time without intervention. Patients often receive surgeries to lengthen tight or spastic muscles or to correct bone malalignments, but outcomes are variable and unpredictable. The goals of this dissertation were, first, to objectively identify biomechanical factors that cause a patient to walk with excess knee flexion and, second, to use these factors to predict whether a patient's crouch gait will improve after receiving treatment. We first determined the influence of abnormal bone geometry and crouched gait postures on the function of muscles during walking using a three-dimensional model of the musculoskeletal system. Our analysis revealed that a tibial torsion deformity, a common bone malalignment, reduces the capacity of lower limb muscles to generate extension of the knee and hip joints. Excess tibial torsion may thus be a significant contributor to crouch gait and warrant surgical correction. In addition, our analysis showed that a crouched gait posture markedly reduces the capacity of most lower limb muscles to extend the knee and hip joints. These findings help explain the altered muscle activations, increased energy requirements, and increased joint loading associated with walking in a crouch gait. We also developed a multi-variable linear regression model to estimate how much subjects' crouch gait would change between hospital visits by retrospectively analyzing patients' gait kinematics over time and surgical histories. The regression model was able to explain 49% of the variance in the change in knee flexion between gait visits for the 353 subject-limbs that we analyzed. Further, the regression model classified subject-limbs as 'Improved' or 'Unimproved' with approximately 70% accuracy, which contrasts with the observed improvement rate of 48% among subject-limbs in the study. We further demonstrated that more improvement in crouch gait was expected when subjects had i) adequate hamstrings lengths and velocities, ii) normal tibial torsion, and iii) greater extensor muscle strength, three variables drawn from our knowledge about the biomechanics of crouch gait. This work establishes a new framework--combining biomechanical modeling and statistical analysis--for understanding gait pathology and objectively planning treatment.