Patella fracture

Background

Anatomy of anterolateral aspect of right knee.

• Occurs via direct blow or forceful contraction of quadriceps muscle
• Do not confuse a bipartite patella with a fracture (bipartite patellas are usually bilateral so may image contralateral knee to confirm)

Clinical Features

• Focal patellar tenderness, swelling, effusion
• Check integrity of knee extensor mechanism by having patient perform straight-leg raise

Differential Diagnosis

Knee diagnoses

Acute knee injury

• Knee dislocation
• Knee fractures
  • Patella fracture
  • Segond fracture
  • Tibial plateau fracture
• Meniscus and ligament knee injuries
• Patella dislocation
• Patellar tendonitis
• Patellar tendon rupture
• Quadriceps tendon rupture

Nontraumatic/Subacute

• Arthritis
• Gout and Pseudogout
• Osgood-Schlatter disease
• Patellofemoral syndrome (Runner's Knee)
• Patellar tendonitis (Jumper's knee)
• Pes anserine bursitis
• Popliteal cyst (Bakers cyst)
• Prepatellar bursitis (nonseptic)
• Septic bursitis
• Septic joint
• DVT

Evaluation

Imaging

• AP and lateral
  • Lateral view: Distance from tibial tubercle:lower pole of patella ~ length of patella +/- 20%
    • If greater than this suspect patellar ligament rupture
• Consider skyline (sunset) view if suspect fracture of articular surface

Management

• Nondisplaced with intact extensor mechanism: knee immobilizer, rest, ice
• Displaced >3mm or disruption of extensor mechanism: above + early referral for ORIF

Disposition

• Outpatient

See Also

• Knee fractures
• Knee (Main)