Non-Identical Bilateral Rupture of the Extensor Mechanism of the Knee in a Patient with Hyperlipidemia: A Case Study

Rupture of the extensor mechanism is a relatively common injury, most frequently occurring as a result of patella fracture, while ruptures of the quadriceps tendon and patellar ligament are less common. Extensor mechanisms of healthy knees are able to tolerate large forces before rupturing; therefore, complete ruptures without significant trauma are due to minor injury to an already degenerate or attenuated tendon. Hyperlipidemia has been linked as a cause of tendon degeneration due to the systemic biological effect that it has on tenocytes. Non-identical bilateral ruptures are rare. To the best of our knowledge, this is the only case report of bilateral ruptures involving the quadriceps tendon of one knee and patellar ligament of the contralateral knee simultaneously.

A 42-year-old man presented to our department with bilateral traumatic rupture of the extensor mechanism of the knee. He had no medical history, was not taking any regular medications, and had no significant family history but a 15-year history of anterior knee pain. Both of his legs gave way on landing from a jump. Radiographs demonstrated a knee effusion with normal patella height on the left and a knee effusion with an elevated patella on the right. A diagnosis of quadriceps tendon rupture on the left and patellar ligament rupture on the right was made.

Hyperlipidemia has been associated with ruptures of the Achilles tendon but has not been reported in association with failure of the extensor mechanism of the knee. We suggest that all patients presenting with bilateral tendon ruptures, especially in the absence of systemic disease or corticosteroid therapy, are investigated for hyperlipidemia and treated accordingly.