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Quadriceps Tendon Rupture

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Other Names

  • Quad Rupture
  • Patellar Tendon Rupture
  • Extensor Mechanism Rupture
  • Knee Extensor Mechanism Rupture




  • Overall scant literature published on the subject due to relative rare injury
  • Greater occurrence with increased age (more common after age 40) and multiple medical comorbidities
  • More prevalent in males
  • Missed diagnosis rate reported to range from 10-50%[1]
  • British study [2]
    • Incidence of quad tendons and patellar tendon ruptures are 1.37 and 0.6 per 100,000 person years
    • In this study, mean age for males was 50.5, females 51.7
  • Quad ruptures[3]
    • More common in patients older than 40 years
    • Associated with degenerative tendon changes
    • Quad tendon ruptures occur approximately 6 times more frequently than patellar rupture[4]
  • Patellar tendon [5]
    • Typically observed in patients younger than 40 years
    • Associated with direct traumatic mechanisms or end-stage patellar tendinopathy


  • Mechanism
    • Can be spontaneous
    • Minor direct trauma following progressive tendon degeneration
    • Violent eccentric contraction of the extensor mechanism.
  • Result of a tensile overload on the extensor mechanism and long-standing chronic tendon degeneration
  • Quadriceps muscle suddenly contracts with the knee in a flexed position (flexed more than 60 degrees)
  • Due to sudden, eccentric contraction of the quadriceps from
    • Jump and land mechanism
    • Sudden change in direction
    • Less commonly, direct trauma
    • Typically involving an eccentric load of the quads
  • Tendon ruptures rarely occur mid substance, more commonly manifest as
    • Avulsion fracture
    • disruptions at the musculotendinous junction
    • disruptions at the osseotendinous junctions
  • Quadriceps Tendon
    • Associated with degenerative changes
  • Patellar Tendon Rupture
    • Involves complete tear of the patellar tendon (connects from the patella's inferior pole to the tibial tubercle)
    • Zernicke et al: a force of 17.5 times body weight is required to cause patellar tendon rupture in healthy patients[6]


  • Quadriceps Femoris formed by the confluence of 4 muscles into the quadriceps tendon:
  • Extensor Mechanism
  • Quad Tendon Injury Location
    • Relatively hypovascular zone exists about 1–2 cm superior to the patella, making it more susceptible to injury[7]
    • In younger folks, the most common sites of tear are between 1 cm and 2 cm of the superior pole of the Patella
    • In older folks, more distally at the osseotendinous junction
  • Patellar Tendon Injury Location
    • Most occur at the inferior patellar pole
    • Proximal avulsion of the tendon, with or without bone from the inferior pole of the patella
    • Midsubstance of the tendon
    • Avulsion of the patellar tendon from the tibial tubercle

Risk Factors

Differential Diagnosis

Differential Diagnosis Thigh Pain

Differential Diagnosis Knee Pain

Clinical Features

  • History
    • Acute injury
    • Commonly hear a pop or tearing sensation
    • Preceding tendinopathy symptoms is common
    • Suprapatellar (quad tendon) or infrapatellar (patellar tendon) pain
    • Inability to bear weight
  • Exam: Physical Exam Knee
    • Tenderness at site of rupture
    • Quad: Palpable defect usually within 2 cm of superior pole of patella
    • Patellar: Palpable defect between inferior pole and tibial tubercle
    • Unable to extend the knee against resistance or gravity
    • Patella: low riding (quad tendon), high riding (patellar tendon)
    • Joint effusion is often present
    • Weak knee extension or extension lag suggests incomplete disruption
    • Decreased ROM
  • Special Tests


Patella alta and inferior patella pole avulsion fracture suspicious for patellar tendon rupture
  • Standard Radiographs Knee
    • AP and lateral of knee
    • Quad Tendon: Patella pulled inferiorly by the Patellar Tendon, termed patella baja
    • Patellar Tendon: Patella is pulled proximally by quad tendon, termed patella alta
    • Avulsion injuries present as patellar or tibial tubercle avulsion fractures
    • Insall-Salvati Ratio is used to evaluate patellar height on the lateral view
US of the knee in quad tendon, long axis. There is a complete tear of the tendon approximately 4 cm proximal to its insertion with a 2.3 cm defect and hematoma[10]


  • Pathologic Findings
    • Complete tear: Hypoechoic area between the two tendon fragments
    • Partial tear: hypopoechoic area with some intact tendon fibers
    • Assess the degree of tendon gap with knee flexion
  • Normal
    • Quad tendon is 6–11 mm thick
    • Linearly oriented homogeneous echoes extending through the length of the tendon


  • May show
    • Differentiates between partial and complete tears
    • Obtain if uncertainty regarding diagnosis
    • Can evaluate for other intra-articular injuries


  • Partial
  • Complete



  • Surgical
    • Boudissa et al found good functional outcomes in 50 patients followed for 6 years for pain, function, range of motion [11]
    • Most studies report good or excellent results ranging from 80 to 92% following surgical repair[12]
  • Return to sport
    • Nguyen et al found NBA players returned to sport at a similar competition level[13]
    • Boublik et al also found NFL players were able to return to a high level of competition[14]


  • General
    • Partial quadriceps tendon ruptures may be managed non-operatively if extensor mechanism intact
    • Partial patellar tendon ruptures may be managed non-operatively if extensor mechanism intact
    • Consider in patients who are poor surgical candidates due to comorbidities
  • Acute Management
  • Quad Tendon
    • Immobilized in full extension for 6 weeks
  • Patellar Tendon
    • Fully immobilized in extension for 2 weeks
    • Begin active/ passive flexion/extension at 4 weeks, strengthening at 6 weeks
  • Effusion should be aggressively managed to minimize tension on extensor mechanism


  • Indications
    • Complete tear
    • Partial or incomplete tear with functional deficit
    • Poor response to conservative measures
  • Technique
    • Primary repair of acute rupture
    • Primary repair of chronic rupture

Rehab and Return to Play


  • In Hinged Knee Brace postoperatively
    • Historically, knee was immobilized in full extension for 6 weeks postoperatively to allow complete tendon healing before stressing extensor mechanism
    • Trend toward early post-operative joint mobilization to reduce joint stiffness and quadriceps atrophy
  • Range of motion
    • Surgeon dependent but can begin as early as week 1 limiting to 45° active flexion and passive extension only
    • On week 2-3 can begin progressive range of motion past 45°, moving only 15° per week
  • Strength
    • Isometric quadriceps and hamstring exercises begin on post op day 1
    • Active knee extension starts at 6 weeks
  • Ambulation
    • Full weight bearing in locked brace, with crutches at 6 weeks
    • Brace and crutches discontinued when adequate quadriceps strength is achieved, usually around 12 weeks[15]

Return to Play

  • Needs to be updated


  • Pain and stiffness
  • Extensor mechanism weakness
  • Functional impairment
  • Strength deficit
  • Re-rupture
  • Extensor lag, inability to fully extend knee
  • Loss of full knee flexion
  • Quadriceps Atrophy

See Also


  1. Rauh M, Parker R. Patellar and quadriceps tendinopathies and ruptures. In: DeLee JC, ed. DeLee and Drez’s Orthopaedic Sports Medicine. Philadelphia, PA: Saunders; 2009:1513–1577
  2. Clayton RAE, Court-Brown CM. The epidemiology of musculoskeletal tendinous and ligamentous injuries. Injury. 2008;39:1338–44.
  3. Ramsey RH, Muller GE. Quadriceps tendon rupture: a diagnostic trap. Clin Orthop Relat Res 1970; 70: 161-164
  4. Saragaglia, D., A. Pison, and B. Rubens-Duval. "Acute and old ruptures of the extensor apparatus of the knee in adults (excluding knee replacement)." Orthopaedics & Traumatology: Surgery & Research 99.1 (2013): S67-S76.
  5. Kannus P, Józsa L. Histopathological changes preceding spontaneous rupture of a tendon. A controlled study of 891 patients. J Bone Joint Surg Am 1991; 73 (10) 1507-1525
  6. Zernicke RF, Garhammer J, Jobe FW. Human patellar-tendon rupture. J Bone Joint Surg Am 1977;59(2):179–183
  7. Yepes H, Tang M, Morris SF, Stanish WD. Relationship between hypovascular zones and patterns of rupture of the quadriceps tendon. J Bone Joint Surg Am. 90:2135–41
  8. Lynch AF, Rorabeck CH, Bourne RB. Extensor mechanism complications following total knee arthroplasty. J Arthroplasty 1987; 2 (2) 135-140
  9. Loehr J, Welsh RP. Spontaneous rupture of the quadriceps tendon and patellar ligament during treatment for chronic renal failure. Can Med Assoc J 1983; 129 (3) 254-256
  10. Case courtesy of Dr Bruno Di Muzio, Radiopaedia.org, rID: 48031
  11. Boudissa, M., et al. "Acute quadriceps tendon ruptures: a series of 50 knees with an average follow-up of more than 6 years." Orthopaedics & Traumatology: Surgery & Research 100.2 (2014): 217-220.
  12. Lee, Dennis, Daniel Stinner, and Hassan Mir. "Quadriceps and patellar tendon ruptures." The journal of knee surgery 26.05 (2013): 301-308.
  13. Nguyen, Michael V., et al. "A comprehensive return-to-play analysis of national basketball association players with operative patellar tendon tears." Orthopaedic journal of sports medicine 6.10 (2018): 2325967118800479.
  14. Boublik M, Schlegel T, Koonce R, Genuario J, Lind C, Hamming D. Patellar Tendon Ruptures in National Football League Players. The American Journal of Sports Medicine. 2011;39(11):2436-2440.
  15. Ilan DI, Tejwani N, Keschner M, Leibman M. Quadriceps tendon rupture. J Am Acad Orthop Surg 2003;11(3):192–200
Created by:
John Kiel on 7 July 2019 06:18:01
Last edited:
4 October 2022 15:48:59
Tendinopathies | Knee | Lower Extremity | Trauma | Thigh | Acute