Knee Anatomy (

Definition:  Rupture of the patellar tendon (tendon attaching patella to tibial tubercle) with or without associated fracture.


  • Overload of the extensor mechanism complex (quadriceps, quadriceps tendon, patella, patellar tendon, tibial tubercle)
  • More likely to occur with knee flexed to 60 degrees, given most force on tendon at this angle (Matava 1996)


  • Uncommon injury: < 1% US population per year (Volpi 2016)
  • Gender: Males > Females   
  • Age: 20s and 30s most commonly
  • More often unilateral, but bilateral patellar tendon rupture has been documented (Matava 1996)
  • Predisposing Factors (Volpi 2016)
    • Previous surgery
    • Patellar tendinopathy
    • SLE
    • Rheumatoid arthritis
    • Chronic renal failure
    • DM

Physical Exam

  • Loss of extensor mechanism (ability to extend at knee joint)
  • Hemarthrosis, swelling, tenderness
  • Palpable defect inferior to patella
  • Patella alta (elevation of patellar height)
  • Inability of unassisted weight bearing (Volk 2014)

Injury Classification

  • Partial tendon rupture – Extensor mechanism intact
  • Complete tendon rupture – Loss of extensor mechanism
    • Tendon avulsion from inferior pole of patella
      • May include bony fragment when associated patellar fracture (McMahon 2014)
    • Mid-tendon rupture
    • Tendon avulsion from tibial tubercle
      • May include bony fragment when associated tibial tubercle fracture
  • Xrays
    • Trauma knee series: AP, lateral, obliques and can consider sunrise/tunnel views if indicated
    • Xray cannot visualize tendon, but may provide other evidence of tendon rupture as shown below

Patella Alta (Case courtesy of From the case rID: 11743)

Patellar Tendon Rupture with Avulsion of Tibial Tubercle (

  • Ultrasound
    • Can aid in diagnosis at bedside using longitudinal view from inferior patella to tibial tuberosity
    • Normal tendon structure can be identified as multiple parallel echogenic lines
    • Rupture can be identified as a hypoechoic break with surrounding edema

Patellar Tendon US Normal (

Ruptured Patellar Tendon (

  • MRI
    • Gold standard for diagnosis
    • Usually unnecessary in ER and can be obtained as out-patient if needed

Emergency Department Management

  • Partial tendon rupture
    • Usually treated non-operatively
    • Knee immobilizer and crutches (non-weight bearing in immediate period)
    • Orthopedic follow up – graded weight bearing as tolerated for 3-6 weeks (Khan 2005)
  • Complete tendon rupture
    • Usually treated with operative repair
    • Prompt follow up necessary (within 1 week)
    • Non-weight bearing with knee immobilizer and crutches
    • Shorter time to surgical repair was associated with better outcomes of recovery – lower incidence of quadriceps weakness and incomplete knee flexion (Matava 1996)
    • Indications for immediate Orthopedic consultation
      • Any associated fracture (e.g. tibial plateau, patellar)
      • Pediatric population
        • Sleeve fractures are often missed due to cartilaginous tendon attachment in children
      • Expected non-compliance with knee immobilization or non-weight beating status


  • For partial tendon rupture, rehabilitation length depends on severity of tear with complete recovery by 6 months
  • For complete tendon rupture, non-restricted activity usually resumes at 4-6 months with complete recovery between 6-12 months (Vopli 2016)

Take Home Points

  • Loss of extensor mechanism is a key part of the knee exam and indicates complete disruption of the patellar tendon (or quadriceps tendon)
  • All patients with patellar tendon rupture should have their knee immobilized, be initially non-weight bearing and follow up promptly with Orthopedics
  • Missed diagnoses and delay of surgical repair can lead to worse outcomes

Read More

OrthoBullets: Patella Tendon Rupture

OrthoBullets: Patella Sleeve Fracture


Khan KM et al. Patellar Tendinopathy and Patellar Tendon Rupture. In: Maffulli N., Renström P., Leadbetter W.B. (eds) Tendon Injuries. 2005. Springer, London (Link)

Matava M. Patellar Tendon Ruptures. J Am Acad Ortho Sure 1996; 4(6): 287–296. PMID: 10797196

McMahon, Patrick J., et al (2014). “Chapter 3. Sports Medicine.” Current Diagnosis & Treatment in Orthopedics, 5e Eds. Harry B. Skinner, and Patrick J. McMahon. New York, NY: McGraw-Hill.

Volk WR et al. Complications in Brief: Quadriceps and patellar tendon tears. Clin Orthop Relat Res 2014; 472(3): 1050-7. PMID: 24338040

Arthroscopy and Sport Injuries : Applications in High-Level Athletes, edited by Piero Volpi, Springer, 2015. ProQuest Ebook Central. Link