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What is the diagnosis?

Patellar Tendon Rupture. A patellar tendon rupture entails a complete tendon tear from the patella's inferior pole to the tibial tubercle [1]. These tendon ruptures can be categorized into acute and chronic tears [2].

What is the expected mechanism of injury?

This usually occurs in the setting of trauma when the tendon is placed under high-tension force on the extensor mechanism [1, 2].

What physical exam findings are expected?

A high riding patella can be seen on physical examination [3]. Tenderness inferior to the patella, and inability to extend the knee against gravity can also be seen on exam. A defect in the patellar tendon and patella alta can commonly be palpated [4].

Which imaging modalities can be used?

A plain X-ray, both in antero-posterior and lateral views, should be obtained which can show patella alta, patellar avulsion, or a tibial tuberosity fracture. MRI is considered to be the gold standard imaging modality but it is not always available [5].

• Pearl: These injuries can also be identified on ultrasound in the ED if that is something that you are comfortable assessing.

Image 2. A high riding patella, also known as patella alta, is seen on the x-ray. Authors’ own image and annotation.

What is the management in the ED?

Place the patient in a knee immobilizer in full extension [1].

• Pearl: Knee immobilizers are typically indicated in extensor mechanism injuries such as this one.

When do you consult Orthopedics?

Though it is not considered to be a surgical emergency, treatment for a complete patellar tendon rupture involves surgical repair [2, 4]. Patients should be referred to be seen by orthopedics surgery for primary surgical repair in a complete patellar tendon rupture within 2 weeks [4, 6].