CASE 53

By: Dr. Subramaniyan Ramanathan MD. And Dr. Mahmoud Alheidous

HISTORY: 23-year-old male with history of sports injury and anterior knee pain.

What are your findings?

What is the differential diagnosis?

What are the causes?

FINDINGS:

Lateral knee radiograph shows small bone fragment close to superior pole patella. Soft tissue swelling noted in the suprapatellar region suggesting joint effusion/hemarthrosis. MRI knee (Sagittal PD and gradient echo) performed after a month shows the avulsion fracture of superior pole of patella at the quadriceps insertion with partial tear of the tendon. Associated mild soft tissue edema seen. Joint effusion has resolved in the MRI.

DIAGNOSIS:

Avulsion fracture of the quadriceps tendon.

PEARLS AND DISCUSSION:

Quadriceps tendon rupture is one of the extensor mechanism of the knee injuries, more common than patellar tendon rupture but less common than patellar fractures. It is usually apparent clinically if it complete. Rupture of the quadriceps tendon is commonly seen at the musculo-tendinous junction and avulsion at tendo-osseous junction can be seen secondary to repetitive microtrauma or systemic diseases like hyperparathyroidism, diabetes, collagen vascular diseases, and gout). Sudden contraction of the quadriceps muscle with the knee flexed during athletic activities such as jumping, and kicking is the proposed mechanism of injury.

On conventional radiography, these fractures are often best appreciated on the lateral view, where comminuted bone fragments arising from the superior aspect of the patella are frequently seen. Patella Baja deformity, which describes an abnormally low position of the patella with respect to the femur, can also be noted. On MRI, sagittal views demonstrate separation of the distal quadriceps tendon from the superior patella as well as marrow edema in the upper patellar pole. A suprapatellar joint effusion is frequently identified as well.

FURTHER READING:

1. Sonin AH, Fitzgerald SW, Bresler ME et-al. MR imaging appearance of the extensor mechanism of the knee: functional anatomy and injury patterns. Radiographics. 1995;15 (2): 367-82. 

2. BencardinoJT, Rosenberg ZS, Brown RR, Hassankhani A, Lustrin ES, Beltran J. Traumatic musculotendinous injuries of the knee: diagnosis with MR imaging. RadioGraphics2000; 20(spec issue): S103–S120

3. Al-Nakshabandi NA. Bilateral chronic quadriceps tendon tears secondary to repeated seizures. Neurosciences (Riyadh) 2006; 11:115–116