Background: Implementation science frameworks aided the development of a new, evidence-based clinical physical therapy program. The purpose of this report is to describe the process of sustaining a clinical program in practice for over four years. We present a framework for integrating tools for sustainability with the Knowledge-to-Action model in the context of a proactive physical therapy program (PAPT) for individuals with early stage Parkinson’s disease.Methods: Sustainability of implementation strategies was addressed using the Dynamic Sustainability Framework and sustainability assessment tools. Repeated retrospective medical record reviews and semi-structured interviews were used to evaluate the reach and adoption of the PAPT over four years. Characteristics of those who engaged with PAPT, implementation fidelity, and clinical effectiveness were assessed for Year 1 and Year 3. Sustainability was measured using RE-AIM, NHS Sustainability Model, and Clinical Sustainability Assessment Tool.Results: Reach increased from 28 to 110 total patients per year and spread occurred from one to three sites. PAPT user age, sex, Hoehn & Yahr rating, time since diagnosis and type of insurance were similar in Year 1 and Year 3 (p>0.05). The program sustained its effect to help participants increase or maintain self-reported exercise (Y1: 95%, Y3: 100%). However, upon evaluation PAPT users in Year 3 had longer time since symptom onset and worse UPDRS motor scores compared to the PAPT users in Year 1 (p<0.05). All sites sustained the core intervention components, with sustainability scores of 71/100 (± 9.9) on the NHS Sustainability Model and 6.1/7 (± 0.9) on the Clinical Sustainability Assessment Tool.Conclusions: Integrating multiple sustainability models and assessments supported continued effectiveness, spread, and sustainment of PAPT for four years. Effective planning, anticipating common healthcare changes, and addressing sustainability determinants early in program implementation were essential aspects of long-term success.