Iatrogenic Femoral Nerve Palsy Masquerading as Knee Extensor Mechanism Rupture

Abstract not available. Introduction provided instead.

Patellar ligament and quadriceps tendon ruptures, often the result of a mechanical load to failure on the tendon, lead to an inability to actively extend the knee. Optimal treatment is immediate repair using any of a number of methods.^1-3

Diagnosis of extensor mechanism rupture of the knee can often be made with a complete history of the event and a physical examination and may be supplemented with radiographic studies. Often there is a history of a fall or hyperflexion injury, a subjective sensation of the involved knee “giving way,” and
difficulty bearing weight after the injury. Examination reveals an inability to actively extend the knee (though an intact extensor retinaculum may allow minimal knee extension), swelling in the region of the patellar ligament or quadriceps tendon, a palpable defect where the tendon would normally reside, and often a superiorly (patellar supera) or inferiorly (patella infera) translated patella. Radiographs often show patella supera or infera, and magnetic resonance imaging
(MRI) can confirm the diagnosis.^1-3

We present the case of a femoral nerve palsy masquerading as a knee extensor mechanism rupture that became symptomatic 1 month after emergent exploratory laparotomy, sigmoid resection, and Hartmann pouch closure for a colon perforation
after colonoscopy. This case highlights the need for a thorough history and physical examination, as well as potential complications of abdominal and pelvic surgery that the orthopedist should be aware of. Furthermore, awareness of this potential confusing clinical situation may avoid an unnecessary surgical intervention
on an intact extensor mechanism despite a clinical examination consistent with knee extensor mechanism rupture.