Patellar fracture

Patellar fractures are the result of blunt trauma to the patella or due to a contracting quadriceps. These fractures are rare, accounting for approximately 1% of all fractures.

Etiology

Fall onto flexed knee or the knee hitting the dashboard during motor vehicle accident are the most frequent causes of patellar fracture.

Classification

Patellar fractures are classified according to their morphology:

• Undisplaced
• Transverse
• Lower or upper pole
• Comminuted undisplaced
• Comminuted displaced
• Vertical
• Osteochondral

Clinical features

Symptoms include swollen knee and patellar pain and tenderness.

Diagnosis and evaluation

During physical examination it’s important to evaluate the extensor function, as disrupted extensor mechanism is an indication for surgery. Patient should be challenged to extend their knee fully against gravity. However, pain may prevent full extension, and it may be difficult to discern whether abnormal extension is due to pain or a disrupted mechanism. Physical examination will likely also reveal intraarticular fluid.

X-ray is usually sufficient for diagnosis. Ultrasound or CT/MRI may be used to exclude other injuries.

Treatment

For undisplaced, closed patella fractures with intact extensor mechanism, conservative treatment is sufficient.

For displaced or avulsed patella fractures, surgery is necessary. Surgery involves tension band wiring or partial patellectomy with anchoring the patella.