Traumatic rupture of the patellar tendon is the result of severe overloading of the extensor mechanism of the knee in young, athletic patients. In contrast, prior injection of steroids and a variety of systemic diseases are associated with an increased tendency to rupture with little or no trauma. The rarity of bilateral patellar tendon rupture and the symmetry of the findings on physical examination may cause clinicians to miss the diagnosis.

We report a case of spontaneous bilateral patellar tendon rupture in a patient with systemic lupus erythematosus. The patient was seen twice in the emergency department without the injury being recognized. This case highlights the potential difficulties in diagnosing atraumatic bilateral patellar tendon rupture.