Disruption of the extensor mechanism of the knee.

Ruptures of the extensor mechanism of the knee are rare, when compared with other knee injuries, and are frequently misdiagnosed. The outcome after surgical repair may be compromised if surgery is delayed. A case of quadriceps tendon rupture that was misdiagnosed for 2 months and a review of the literature are presented. Including extensor mechanism disruption in the differential diagnosis, and careful attention to key physical findings in the examination of all acutely injured knees, will ensure that this important injury is not overlooked.