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Infrapatellar Fat Pad Impingement

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Other Names

  • Infrapatellar fat pad impingement
  • Fat Pad Syndrome
  • Hoffa's Syndrome
  • Hoffa's Fat Pad Syndrome
  • Hoffa's disease
  • Fat pad herniation



  • First described by Hoffa in 1904[1]


  • Overall, poorly described in the literature
    • Much of the literature is based on case reports and case series
  • Kumar et al report a series of 2623 patients undergoing knee arthroscopy (need citation)
    • IFP impingement in as an isolated lesion in 34 (1.3%) patients
    • Coexisting with other pathologies as secondary disease in 178 cases (6.8%)
  • Ogilvie-Haris and Giddens 10 year study of 1200 patients (need citation)
    • Report incidence IFP Impingement of 1%


  • General
    • Disease process suffers from a paucity of literature
    • The IFP is a intracapsular, extrasynovial adipose tissue structure in the anterior knee
    • Important source of anterior knee pain
  • Etiology
    • Overall, poorly understood
    • IFP impingement has been termed 'an impingement of the hypertrophic fat pad between the articular surfaces of the knee'
    • Specifically, the IFP is impinged between the Patella and Medial Femoral Condyle
    • Alternatively may impinge between the femur and tibia during extension[2]
    • Leads to inflammation, hypertrophy, chronic inflammation with necrosis and fibrosis
  • Pathology thought to be caused due to
    • Inflammation and fibrosis associated with trauma
    • Trauma may be direct blow, acute hyperextension, chronic irritation or postsurgical scarring


  • Pediatric population
    • IFP can herniate through a defect in the lateral retinaculum
    • Will present as painless, atraumatic mass in the anterolateral infrapatellar region


  • Infrapatellar Fat Pad
    • Intracapsular and extrasynovial adipose tissue structure
    • Heavily vascularized, highly innervated
    • Largest soft tissue structure in the knee joint
  • Function
    • Biochemical: reservoir rich in stem cells, may contribute to healing response after injury
    • Biomechanical: dynamic structure which can change in shape during knee motion, stabilizing patella and patellar tendon
  • Borders[3]
    • Anterior: Patellar Tendon, joint capsule
    • Superior: inferior pole of the Patella
    • Inferior: proximal Tibia, deep infrapatellar bursa, intermeniscal ligament, meniscal horns and infrapatellar bursa
    • Posterior: joint synovium, femoral condyles and intercondylar notch.
  • Attachments[4]
    • intercondylar notch via the ligamentum mucosum
    • Anterior horns of the menisci
    • Proximal end of the patella tendon
    • Inferior pole of the patella
  • Description
    • Consists of a central body with medial and lateral extensions
    • There is a vertical cleft in the superior aspect of the fat pad
    • Horizontal cleft in the postroinferior aspect of the fat pad
  • Vascular Supply
    • Upper and lower geniculate arteries create abundant peripheral anastamotic blood supply
    • Supromedial and suprolateral geniculate arteries provide 2 vertical arteries
    • 2 or 3 horizontal arteries connect the vertical arteries
  • Innervation

Risk Factors

  • Female > Male (need citation)
  • Sports that require forceful extension of the knee[5]
    • Dance
    • Gymnastics
    • Swimming
    • Martial arts
    • Jumping events (high jump, long jump, triple jump)

Differential Diagnosis

Clinical Features

  • History
    • Patients typically endorse anterior knee pain
    • Duration of symptoms can range from weeks, months to even years
    • Symptoms are worse with activity
    • Some patients may have a history of mild or repetitive trauma, usually related to activity or sports
  • Physical Exam: Physical Exam Knee
    • Joint effusion may or may not be present
    • Pain, tenderness around the patella especially at the inferior pole
    • Range of motion may be restricted
    • Pain at terminal extension
  • Special Tests
    • Hoffas Test: pain with pressure on medial or lateral side of patella with knee in extension




  • Findings[6]
    • Hypointensity lesions
    • Ossified lesion
    • Solitary nonossified lesions
    • Localized edema of the superior and/or posterior part of the infrapatellar fat pad
    • Deep fluid-filled infrapatellar bursa
    • Nonvisualization of vertical and/or horizontal clefts
    • Fibrosis or calcification of the fat pad
  • Clinical correlation with MRI findings[7]
    • Specific edema locations do not correlate with clinical infrapatellar fat pad impingement
    • Patients with clinical symptoms do have more regions of edema
    • Second group only 4/47 patients with fat pad edema had symptoms of IFP impingement


  • Findings
    • Enlargement and/or decreased echogenicity within the IPFP
    • Color doppler: increased vascularity suggesting inflammation
  • Dynamic ultrasound
    • Can demonstrate impingement of fat pad during terminal extension
    • Useful to evaluate suspected herniating IFP (see in flexion, absent in extension)


  • None



  • Indications
    • First line therapy in all cases
  • Relative rest
  • Brace
  • Ice Therapy
  • Physical Therapy
    • Emphasis on strengthening quadriceps
  • Corticosteroid Injections
  • Fat Pad Sclerosis and Ablation[8]
    • House and Connell injected the IFP of 12 patients with alcohol and bupivicaine under US guidance
    • The injections were repeated at 3 week intervals for an average of 4 times per patient
    • Patients had an average of 62% decrease in symptoms at 6 weeks of follow up


  • Indications
    • Failure of conservative measures
  • Technique
    • Arthroscopic resection of IFP
    • Repair of lateral retinaculum (for herniating IFP)

Rehab and Return to Play


  • Needs to be updated

Return to Play

  • Needs to be updated

Complications and Prognosis


  • General[9]
    • All studies demonstrate improvement or resolution of symptoms at final follow-up
    • This is true regardless of whether they were treated surgically or nonsurgically
    • Most studies report restoration of range of motion, return to function
  • Genin et al review of case reports[9]
    • 10/14 patients required surgical intervention after unsuccessful nonoperative management
  • Larbi et al describes successfully treating 4/5 patients with nonoperative management[10]
  • Kumar et al described outcomes of 34 patients treated with arthroscopic resection[11]
    • All had substantial improvements in activity levels at 3 months and 1 year
    • 30 patients retured to preinjury activity level
  • Ogilvie-Harris described 11 patients managed with arthroscopic resection[12]
    • there were statistically significant improvement in functional scores and Cincinnati Rating System


  • Chronic knee pain
  • Inability to return to sport

See Also


  1. Hoffa A. The influence of the adipose tissue with regard to the pathology of the knee joint. JAMA 1904;43(12):795–796
  2. Larbi, A., et al. "Hoffa's disease: a report on 5 cases." Diagnostic and interventional imaging 95.11 (2014): 1079-1084.
  3. Draghi F, Ferrozzi G, Urciuoli L, Bortolotto C, Bianchi S. Hoffa’s fat pad abnormalities, knee pain andmagnetic resonance imaging in daily practice. Insights Imaging 2016;7(03):373–383
  4. Gallagher J et al. The infrapatellar fat pad : anatomy and clinical correlations. Knee Surg Sports Traumatol Arthrosc 2005 ; 13 : 268-272.
  5. Bernhardt, D. T. "Overuse injuries of the knee." Care of the young athlete. 2nd ed. Elk Grove Village, Illinois: American Academy of Orthopedic Surgeons, American Academy of Pediatrics (2010): 421.
  6. von Engelhardt LV, Tokmakidis E, Lahner M, et al. Hoffa’s fat pad impingement treated arthroscopically: related findings on preoperative MRI in a case series of 62 patients. Arch Orthop Trauma Surg 2010;130(08):1041–1051
  7. De Smet AA, Davis KW, Dahab KS, Blankenbaker DG, del Rio AM, Bernhardt DT. Is there an association between superolateral Hoffa fat pad edema on MRI and clinical evidence of fat pad impingement? AJR Am J Roentgenol 2012;199(05):1099–1104
  8. House CV, Connell DA. Therapeutic ablation of the infrapatellar fat pad under ultrasound guidance: a pilot study. Clin Radiol 2007;62(12):1198–1201
  9. 9.0 9.1 Genin, Jason, et al. "Infrapatellar fat pad impingement: a systematic review." The journal of knee surgery 30.07 (2017): 639-646.
  10. Larbi A, Cyteval C, Hamoui M, et al. Hoffa’s disease: a report on 5 cases. Diagn Interv Imaging 2014;95(11):1079–1084
  11. Kumar D, Alvand A, Beacon JP. Impingement of infrapatellar fat pad (Hoffa’s disease): results of high-portal arthroscopic resection. Arthroscopy 2007;23(11):1180–1186.e1
  12. Ogilvie-Harris DJ, Giddens J. Hoffa’s disease: arthroscopic resection of the infrapatellar fat pad. Arthroscopy 1994;10(02):184–187
Created by:
John Kiel on 7 July 2019 05:30:07
Last edited:
4 October 2022 15:55:18