II. Risk Factors

  1. Patellar Tendinopathy may predispose to Patellar Tendon Rupture

III. Mechanism

  1. Forceful knee flexion against resistance

IV. Signs:

  1. Large Knee Effusion
  2. Defect between tibial tubercle and inferior Patella
  3. Difficult active knee extension
    1. Some knee extension may be maintained if Patellar Retinacular fibers are intact

V. Differential Diagnosis

  1. Patellar Dislocation
  2. Quadriceps tendon rupture (elderly)
  3. Tibial tuberosity avulsion (adolescents)

VI. Imaging: Knee XRay

  1. Insall-Salvati Ratio for Patella evaluation
    1. Distance ratio between
      1. Proximal tibial tubercle
      2. Inferior pole of the Patella
    2. Normal ratio: +1 or -0.2
  2. Interpretation: Severe Patella alta (high riding)
    1. Suggests Patellar ligament rupture
  3. Other findings
    1. Patella avulsion Fracture

VII. Imaging: Advanced

  1. Knee Bedside Ultrasound
    1. Ruptured tendon will appear hypoechogenic with a separation between tendon ends
    2. Dynamic views may better define the tendon ends
  2. Knee MRI
    1. Definitive study to identify extent of rupture and plan surgical repair

VIII. Management

  1. Surgical Correction within 10 days of injury
  2. Cast immobilization for 6 weeks following surgery
  3. Physical therapy

IX. Complications: Associated with delayed surgery

  1. Quadriceps contracture shortens extensor mechanism

X. References

  1. Hoppman and Shannon (2021) Crit Dec Emerg Med 35(11): 16-7

Images: Related links to external sites (from Bing)

Related Studies