Introduction Corticosteroid injections (CSIs) are commonly used as an initial or a primary intervention for knee osteoarthritis (OA). Consistent evidence indicates CSIs offer symptom relief with conflicting reports regarding long-term efficacy. Physical therapy (PT) offers a non-invasive alternative. There is moderate evidence suggesting short-term and long-term symptom relief and functional improvement with PT interventions. Patients with knee OA are more commonly prescribed CSI than PT prior to total joint replacement. UnitedHealthcare and Military Health System data show substantially more total knee replacement patients receive preoperative CSI than PT. There are no studies comparing CSI to a PT approach in individuals with knee OA. The primary objective of this study is to compare the effectiveness of CSI to PT in individuals with knee OA at 1, 2 and 12 months.

Methods and analysis We plan to recruit 156 participants meeting established knee OA criteria. Following informed consent, participants will be randomised to receive either CSI or PT. All participants will receive instruction on recommended exercise and weight control strategies plus usual medical care. The CSI intervention consisting of 3 injections and the PT intervention consisting of 8–12 sessions will be spaced over 12 months. Measures of the dependent variables (DVs) will occur at baseline, 4 weeks, 8 weeks, 6 months and 12 months post enrolment. This pragmatic, randomised clinical trial will be a mixed-model 2×5 factorial design. The independent variables are treatment (CSI and PT) and time with five levels from baseline to 1 year. The primary DV is the Western Ontario & McMaster Universities Arthritis Index (WOMAC). We will also compare healthcare utilisation between the 2 groups.

Ethics and Dissemination The protocol was approved by the Madigan Army Medical Center Institutional Review Board. The authors intend to publish the results in a peer-reviewed source.

Trial Registration Number NCT01427153.