[Quadriceps tendon rupture]

The quadriceps tendon often ruptures spontaneously without trauma, frequently following an eccentric load on the tendon (walking down stairs) in the case of a previous degenerative injury. Rupture after endoprosthetic knee replacement is a special etiological case. Predominantly men between 50 and 65 years of age are affected. Clinical signs are suprapatellar hematoma and the inability to actively straighten the knee. A typical examination finding is the "suprapatellar gap sign". Ultrasonography is the diagnostic imaging modality of first choice as it can be reliably visualize the rupture and the resulting hematoma. Magnetic resonance imaging has a high sensitivity and specificity for detecting quadriceps tendon ruptures. However, its limited availability should not delay therapy. The treatment of choice is surgical transosseous refixation of the tendon at the upper patellar pole. Following surgery, a straight splint, partial weight bearing and limited mobility are required for 6-8 weeks.