Patellar tendon rupture

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Anatomy of anterolateral aspect of right knee.
  • Occurs via forceful contraction of quadriceps muscle or falling on flexed knee
  • Typically occur 2cm from insertion on patella

Clinical Features

  • Sudden "pop" or tearing
  • Diffuse swelling
  • Defect may be palpable below the patella
  • Partial tears lead to difficulty extending the knee
  • Complete tears lead to absent straight leg raise while supine or extension of the knee again

Differential Diagnosis

Knee diagnoses

Acute knee injury



Patellar tendon rupture[1]
  • Ultrasound
    • Separation of the tendon can be visualized
  • X-ray
    • Patella alta (high-riding patella)

Patellar vs Quadriceps tendon rupture

Finding Patellar tendon rupture Quadriceps tendon rupture
Location Distal to patella Proximal to patella
Typical group Patients <40yr with history of tendinitis or steroid injections Patients >40yr
X-ray Patella alta (high-riding patella) Patella baja/infera (low-riding patella)


  • Ortho consult in the ED
  • Knee immobilizer, can be weight bearing
  • Operative repair advised within 7 days


  • Outpatient

See Also


  • Wheeless' Textbook of Orthopaedics