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From the EMDaily Archives: What’s the Diagnosis? By Dr. Abby Renko

A 45 year old male with a history of ESRD on hemodialysis and insulin dependent diabetes presents with left knee pain after slipping at work. Vitals are within normal limits. On exam, the left lower extremity is distally neurovascularly intact with palpable distal pulses. There is obvious swelling over the knee with the worst pain superior to the patella. He is unable to extend the lower leg. An x-ray is performed and shown below. What’s the diagnosis?

Answer: quadriceps tendon rupture

  • At first glance, lateral XR does not show obvious deformity… however, you may notice calcifications just superior to the patella representing retracted tendon.
  • Quadriceps tendon ruptures tend to occur in individuals > 40, while patellar tendon ruptures occur more frequently in individuals < 40.
    • Overall, quadricep tendon ruptures are more common (risk factors include rheumatologic disease, renal failure, DM, chronic steroid use).
  • In both injuries, classic exam finding is inability to extend the knee. You can often palpate a defect just above the patella in quadriceps tendon ruptures.
  • High riding patella (“patella alta”) on lateral films is more frequently seen in patellar tendon ruptures. Low riding patella (“patella baja”) may be seen on lateral film with complete quadricep tendon tear (intact patellar tendon displaces patella inferiorly).
  • X-rays may be normal! Ultrasound is the diagnostic modality of choice in the ED as it has both high sensitivity and specificity.
  • Orthopedic consultation is always warranted for these cases. Management involves a knee immobilizer and prompt follow up. Early surgical repair is associated with better outcomes in severe cases.


Bengtzen RR, Glaspy JN, Steele MT. Knee Injuries. In: Tintinalli JE, Stapczynski JS, et al., eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide. 8th ed. New York, NY: McGraw-Hill; 2016: (Ch) 274. 

Pope JD, El Bitar Y, Mabrouk A, et al. Quadriceps Tendon Rupture. [Updated 2023 Apr 22]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from:

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