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Patellar Apophysitis

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Other Names

  • Traction apophysitis of the knee
  • Sinding-Larsen-Johansson Disease
  • Sinding Larsen Johansson Disease (SLJ)
  • Superior Patellar Pole Apophysitis
  • Inferior Patellar Pole Apophysitis


  • This page describes apophysitis of the inferior pole of the Patella, an overuse injury
  • Overall, this disease suffers from a dearth of information in the literature



  • Seen in adolescents age 10-14 years of age[1]
  • Males > females
  • Common in middle school athletes[2]
  • More likely to occur during practice than competition


Anatomic illustration of Sinding Larsen Johansson Syndrome.jpg
  • General
    • Overuse injury at the inferior pole of patella at the proximal patella tendon attachment
    • Repetitive traction on the patellar ligament due to quadriceps contraction causes inflammation of patellar tendon attachment
    • Leads to cartilage damage, swelling and pain
    • Later to tendon thickening and fragmentation of the lower pole of the patella
    • Present in skeletally immature adolescents (age 10-14)
  • Considered stress fractures of the apophyseal physis
  • Etiology
    • Regular physical activity
    • Excessive physical activity is most common (i.e. overuse)
    • Direct trauma to the inferior pole of the patella

Associated Pathology


Risk Factors

  • General
    • Middle school athletes[2]
    • Practice > competition
    • Involvement in competitive sport at the age (around 5 or 6 years old) in which the patella begins its ossification
    • Sport specialization
  • Sports (high demands on the extensor apparatus)[4]
    • Football
    • Running
    • Volleyball
    • Gymnastics
    • Long Jump
    • Karate
  • Biomechanical/ Structural[5]
    • Short hamstring tendon
    • Increased posterior tibial slope

Differential Diagnosis

Clinical Features

  • History
    • History of insidious onset of pain on anterior aspect of knee
    • Duration is weeks to months
    • Worse when patella is loaded (running, jumping, sudden stops)[6]
  • Physical Exam: Physical Exam Knee
    • Tenderness over inferior patella, may extend into tendon
    • Swelling over inferior patella, Knee Effusion should be absent
    • Range of motion normal or slightly limited in flexion due to pain
    • Strength and extension should be intact but painful
  • Special Tests
    • Jump Test: Pain is easily reproduced with repetitive jumping in examination room


Lateral left knee radiograph with arrow demonstrating loose bony fragments at inferior patellar pole[7]


  • Standard Radiographs Knee
  • Findings
    • May be normal or show spur at inferior pole of patella
    • Soft tissue swelling may be noted on lateral view
    • Can see calcifications at the origin of the patellar tendon[8]
Focal thickening, increased echogenicity of the right infrapatellar tendon (compared to left). Arrow indicates significant widening, cortical irregularity associated with the apophysis of the patellar apex.[7]


  • General
    • Imaging modality of choice as it can identify all pathology associated with the disease
    • May follow serially over time to examine for progression/resolution of disease
  • Findings[9]
    • Cartilage swelling or thickening
    • Tendon thickening
    • Fragmentation of the lower pole
    • Infrapatallar bursitis
    • Hyperemic tendon fibers with power doppler


    • If diagnosis unclear
    • Help distinguish from from patellar sleeve avulsion


Unknown Classification System

  • Stage 1: Pain occurs after activity
  • Stage 2: Pain present while performing activity and persists after activity
  • Stage 3: Pain affecting/limiting function during activity

Iwamoto Classification System

  • Based on radiographic findings[10]
  • Stage 1: Normal findings.
  • Stage 2: Irregular calcifications at the inferior patellar pole.
  • Stage 3: Coalescence of calcifications.
  • Stage 4A: Incorporation of calcifications into patella.
  • Stage 4B: Coalesced calcified mass separate from the patella



  • Mainstay of treatment, usually self limited
  • Activity modification
    • Abstain for 1-2 months minimum
    • Consider replacing with swimming, other sports that dont use quadriceps muscle as much
  • Physical therapy
    • Improve hamstring, quadriceps and heel cord flexibility
  • Patellar Tendon Counterforce Strap
    • May provide relief, can be worn as needed
  • Consider biomechanical evaluation if not improving
    • Look for knee twisting, valgus moment
    • Neuromuscular deficits
  • Contraindicated


  • Indications
    • Refractory to nonoperative treatment
  • Technique
    • Debridement of damaged tissue/stimulation of healing response

Rehab and Return to Play


  • Needs to be updated

Return to Play

  • Full recovery typically takes 12-24 months

Complications and Prognosis


  • Generally considered a self-limiting condition
  • Full recovery typically takes 12-24 months
  • Symptoms often resolve completely when ossification of the patella is complete[11]


  • Rare
  • Delayed return to sport

See Also


  1. Valentino M, Quiligotti CRM. Sinding-Larsen-Johansson syndrome: a case report. J Ultrasound. 2012;15:127–129.
  2. 2.0 2.1 Foss, Kim D. Barber, Greg D. Myer, and Timothy E. Hewett. "Epidemiology of basketball, soccer, and volleyball injuries in middle-school female athletes." The Physician and sportsmedicine 42.2 (2014): 146-153.
  3. Atanda Jr, Alfred, Suken A. Shah, and Kathleen O'brien. "Osteochondrosis: common causes of pain in growing bones." American family physician 83.3 (2011): 285-291.
  4. Iwamoto J, Takeda T, Sato Y, Matsumoto H. Radiographic abnormalities of the inferior pole of the patella in juvenile athletes. Keio J Med 2009 Mar;58(1):50e3.
  5. López-Alameda, S., et al. "Sinding-Larsen-Johansson disease: analysis of the associated factors." Revista Española de Cirugía Ortopédica y Traumatología (English Edition) 56.5 (2012): 354-360.
  6. Browne, Gary J., and Peter LJ Barnett. "Common sports‐related musculoskeletal injuries presenting to the emergency department." Journal of paediatrics and child health 52.2 (2016): 231-236.
  7. 7.0 7.1 Malherbe, Kathryn. "Traction apophysitis of the knee: A case report." Radiology case reports 14.1 (2019): 18-21.
  8. A G Orthopaedic radiology: a practical approach. 3rd ed. Lippincott Williams & Wilkins.
  9. Draghi F, Danesino GM, Coscia D, Precerutti M, Pagani C. Overload syndromes of the knee in adolescents: sonographic findings. J Ultrasound 2008;11:151e7.
  10. Iwamoto J, Tsuyoshi T, Sato YMH. Radiographic abnormalities of the Inferior pole of the Patella in Juvenile athletes. Keio J Med. 2009;58(1):50–53.
  11. Freedman DM, Kono M, Johnson EE. Pathologic patellar fracture at the site of an old Sinding-Larsen-Johansson lesion: a case report of a 33-year-old male. J Orthop Trauma 2005 Sep;19(8): 582e5
Created by:
John Kiel on 30 June 2019 20:33:03
Last edited:
4 October 2022 15:56:57