AIMS: The aim of this study was to determine the feasibility of a full-scale randomized controlled trial (RCT) comparing two exercise-based rehabilitation interventions for patients with an acute patellar dislocation. METHODS: A two-group external pilot RCT and embedded qualitative study was conducted in five English NHS hospitals. Patients were aged ≥ 14 years with an acute (recruited ≤ 21 days of injury) first-time or recurrent patellar dislocation. Randomization was 1:1 to supervised rehabilitation (between four and six physiotherapy sessions of tailored advice and prescribed home exercises) or self-managed rehabilitation (one physiotherapy session of advice, exercise instruction, and the provision of materials to guide self-management). Quantitative feasibility objectives were: patients' willingness to be randomized; patient recruitment; adherence to the intervention (overall proportion of supervised rehabilitation patients who attended at least four physiotherapy sessions and self-managed rehabilitation patients who attended at least one session); and retention. Follow-up was at three, six, and nine months after randomization. There was no blinding. Semistructured interviews aimed to understand patients' experience of recovery, and the acceptability to them of the interventions and the methods of follow-up. RESULTS: A total of 50 of 88 eligible patients (57% (95% CI 46 to 67)) were willing to be randomized. Sites recruited a mean of 1.4 patients per month (95% CI 0.6 to 1.8), the rate of adherence to the intervention was 72% (95% CI 58 to 83), and the rate of retention at nine months was 62% (95% CI 48 to 74). During follow-up, three patients redislocated the index patella and another underwent patellar stabilization surgery. Interviews with nine patients showed that the experience of recovery was conveyed through the themes 'coming to terms with the initial injury' and 'regaining my former self'. Interviews also indicated that the interventions and methods of follow-up were generally acceptable to patients. CONCLUSION: A full-scale RCT comparing two exercise-based rehabilitation interventions for patients with an acute patellar dislocation is feasible with minor modifications. Modifications should prioritize improving retention and attendance at physiotherapy sessions.