Dynamic Ultrasound Uniquely Reveals Anterior Capsular Tear Communicating With Vastus Intermedius Fibers

We present a case of an anterior capsular tear of the right knee in a previously healthy, active individual. The patient was a 31-year-old male seen one month after the onset of throbbing anterior right knee pain, which progressed to sharp suprapatellar pain over the next three months. Both dynamic ultrasound (US) and MRI were obtained. Dynamic US revealed a tear of the anterior capsule of the right knee complicated by a suprapatellar effusion communicating into the vastus intermedius fibers of the quadriceps tendon. However, these findings were not evident on MRI. In addition to discussing this unique pathology, we highlight the utility of both standard and dynamic US in establishing diagnoses for capsular pathologies.