Ultrasound diagnosis of quadriceps tendon tear in an uncooperative patient

A 38-year-old intoxicated man presented to the emergency department with a painful, swollen left knee and inability to ambulate after being tackled to the ground. The patient was uncooperative, and physical examination of the lower extremities was limited by his intoxication. Radiographic examination of the knee was unremarkable. Ultrasound of the knee revealed a quadriceps tendon rupture. The sonographic features of quadriceps tendon rupture are described, as is the role ultrasound plays in the assessment of a swollen, painful knee.