OBJECTIVE:To report the appearances of ultrasound (US) and magnetic resonance imaging (MRI) before and after surgery for chronic patellar tendinopathy and to correlate postoperative appearances with clinical outcome. DESIGN:A 12-month prospective longitudinal study and a retrospective study, each part using different patients. Prospective study included clinical assessment, ultrasound, and MRI all performed before and 12 months after surgery. Retrospective study included ultrasound and clinical assessment only (i.e., no MRI) 24 to 67 months after surgery. SETTING:Institutional athlete study group in Australia (Victorian Institute of Sport Tendon Study Group). PATIENTS:In the prospective study, 13 patients (all male; 15 tendons) who underwent patellar tenotomy; in the retrospective study, 17 different patients (18 tendons) who had undergone identical surgery. MAIN OUTCOME MEASURES:Ultrasound and MRI appearances and clinical assessment at baseline and 12 months after surgery (prospective study). Ultrasound appearance and clinical assessment 24 to 67 months after surgery (retrospective study). Dimensions of abnormal regions on imaging were measured. Clinical assessment included categorical rating and numerical Victorian Institute of Sport Assessment (VISA) score. RESULTS:In the prospective study, preoperative ultrasound and MRI appearances confirmed the clinical diagnosis of patellar tendinopathy. Postoperative ultrasound and MRI also revealed abnormalities consistent with patellar tendinopathy. Despite this, 11 of 15 (73%) tendons were rated clinically as either good or excellent. Imaging modalities were unable to distinguish tendons rated as good or excellent from those rated poor at 12 months. In the retrospective study, ultrasound images revealed abnormalities despite full clinical recovery. There was no correlation between dimension of ultrasound abnormality and either VISA score or time since surgery. CONCLUSION:After open patellar tenotomy, MRI and ultrasound findings remain abnormal despite clinical recovery. Thus, clinicians ought to base postoperative management of patients undergoing patellar tenotomy on clinical grounds rather than imaging findings. At present, there appears to be no role for routine postoperative imaging of patients recovering slowly after patellar tenotomy. However, this is not to suggest that imaging cannot play a role in special circumstances.