Human locomotion is inherently the most instinctive human movement, yet it stands as one of the most intricate. Its acquisition and development transpire across multiple stages of growth, from infancy through approximately 8 years of age. Pathological conditions have the potential to hinder walking, as exemplified in cases of cerebral palsy (CP) and total knee arthroplasty (TKA). Clinical movement analysis has long been established as a recognized methodology for quantifying human ambulation, notably walking. Consequently, it has evolved into an indispensable tool for clinical decision-making and assessing treatment outcomes in the context of restoring locomotion. The initial part of this Privat Docent thesis underscores the significance of gait and its deviations in cerebral palsy and knee osteoarthritis. Subsequently, functional gait assessment is introduced within the framework of the International Classification of Functioning, Disability and Health (ICF). The concept of Clinical Gait Analysis (CGA) is also elaborated upon, accompanied by a brief historical overview. Lastly, potential strategies for gait rehabilitation are explored, tailored to the context of CP and Knee OA. The second and third sections are parallel components, each dedicated respectively to CP and TKA. Within these sections, we present a comprehensive overview of the diverse studies conducted within these two research domains, with a primary focus on clinical decision-making and the efficacy evaluation of employed treatment modalities. The fourth and fifth sections encapsulate the core findings of the undertaken work, while simultaneously ushering in a range of prospects and potential avenues for future research endeavors.