patellar tendon rupture

Patellar tendon rupture is one of the extensor mechanism of the knee injuries and occurs almost invariably at either the patellar or tibial insertion of the patellar tendon, when in the setting of trauma, and is often associated with a small avulsion fracture. Most commonly, it is at the superior attachment to the inferior pole of the patella. When secondary to systemic illness, then mid-substance tears are more frequent.

Epidemiology

Patellar tendon rupture is less frequent than a patellar fracture and a quadriceps tendon rupture, and tends to occur in a younger population.

Risk factors

Radiographic features

Plain radiograph/MRI

On imaging, a complete rupture is usually easily identified, due to significant patella alta where there is an increased Insall-Salvati ratio.

Other features include blurring of the posterior margin of the patella tendon into the Hoffa fat pad and presence of an avulsion fracture.

Ultrasound

Best imaged with longitudinal scans using high-frequency linear transducers; the tendon normally appears as a continuous well-defined hyperechoic fibrillar structure bridging the patella and the tibial tuberosity while tears usually appear as hypoechoic areas of interruption of the fibrillar pattern .

Treatment and prognosis

Early surgical repair may be necessary to ensure good functional outcome.