In the absence of systemic disease, specific treatment or sport tendonitis, simultaneous bilateral patellar tendon rupture is rare. Often missed on the first glance, it represents a diagnostic difficulty that should not be overlooked at the initial medical visit. The loss of active extension of the lower limb and a radiographic patella alta, even in a bilateral context, should raise suspicion of this diagnosis. It is then necessary to search for predisposing causes and to evoke the differential, or frequently associated, diagnoses. The present report illustrates these diagnostic difficulties and summarizes some clinical considerations that might help to avoid neglecting these different elements at the first medical visit (positive diagnosis, associated lesions, favouring factors).