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Hoffa Fat Pad Syndrome

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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
  • Infrapatellar Fat Pad Impingement
  • Infrapatellar Fat Pad Syndrome
  • Hoffa’s Disease
  • Hoffa Syndrome
  • Infrapatellar Fat Pad Inflammation
  • Anterior Infrapatellar Fat Pad Impingement

Background

History

  • First described by Hoffa in 1904[1]

Epidemiology

  • 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%

Introduction

a Schematic of IFP as both a site and a source of inflammation in the joint, and a contributor to the inflammatory synovial milieu in OA. In addition, IFP can be a rich source of MSCs that can modulate inflammation and potentially play a role in joint tissue repair. b Sagittal proton density fat-suppressed Magnetic Resonance image demonstrating altered signal within Hoffa’s (yellow arrow) and the suprapatellar fat pads (white arrow) in a patient with knee OA[2]
Sagittal view of Infrapatellar Fat Pad[2]
Clinical anatomy of hoffa fat pad syndrome[3]

General

  • Fat pad syndrome is characterized by inflammation, hypertrophy, and fibrosis of the infrapatellar fat pad
  • Occurs in response to repetitive trauma or impingement, presenting most commonly with anterior knee pain
  • The diagnosis is clinical and supported by MRI and ultrasound
  • Treatment is conservative including NSAIDS, physical therapy, corticosteroid injections and rarely surgery

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[4]
    • 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

Herniation

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

Associated Conditions

Anatomy of the Infrapatellar Fat Pad

  • General
    • 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[8]
    • 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[9]
    • 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

Risk Factors

  • Female > Male (need citation)
  • Sports that require forceful extension of the knee[10]
    • Dance
    • Gymnastics
    • Swimming
    • Martial arts
    • Jumping events (high jump, long jump, triple jump)

Differential Diagnosis

Differential Diagnosis Knee Pain

Clinical Features

Demonstration of Hoffas Test[11]

History

  • Patients typically endorse anterior knee pain
    • The pain can be dificult to localize precisely
    • Pain is worse with knee flexion and extension, particularly at terminal ranges[12]
    • Symptoms are worse with activity
    • Occurs after reptitive trauma or prolonged activity such as running[13]
  • Duration of symptoms can range from weeks, months to even years
  • Some patients may have a history of mild or repetitive trauma, usually related to activity or sports
  • There may be an associated sensation of catching
  • Symptoms might develop following knee surgery, arthroscopy, or in the setting of patellar maltracking or ACL deficiency

Physical Exam: Physical Exam Knee

  • Joint effusion may or may not be present
  • Pain, tenderness around the patella especially at the inferior pole[13]
    • Particularly along the medial and lateral borders
  • Range of motion may be restricted
  • Pain at terminal extension which compresses the fat pad posteriorly
  • Possible palpable fullness or swelling in the anterior knee compartment[14]

Special Tests

  • Hoffas Test: pain with pressure on medial or lateral side of patella with knee in extension

Evaluation

Right lateral knee X-ray showing osseous lesion in infrapatellar fat pad, opacities consistent with calcified loose body in the suprapatellar bursa, narrowing of the knee joint space, and osteophitic changes in femoral condyles and tibia.[15]
Bilateral superolateral infrapatellar fat pad (Hoffa fat pad) impingement in a 28 yearold woman with bilateral anterior knee pain due to patellar maltracking. Sagittal fat-suppressed proton-density magnetic resonance (MR) images (A) of the right and (B) left knees show increased signal (arrow) in the superolateral aspect of Hoffa fat pad bilaterally. Note bilateral high-riding patella with modified Insall-Salvati index of 2.2: the distance between distal patellar articular surface and distal patellar tendon insertion (dashed double end arrow)/patellar length (solid double end arrow) is greater than 2. (C) three dimensional (3D) volume rendered image of both knees shows bilateral lateral patellar tilt (curved arrows), lateral patellar shift with and increased tibial tubercle-femoral trochlear distance (2 cm bilaterally) (double end arrows).[16]

Radiographs

  • Standard Radiographs Knee
    • May be normal
    • Important to exclude alternative diagnosis
  • Findings
    • Small effusion
    • Case reports have shown calcifications, opacity[17]

MRI

  • General
    • Imaging modality of choice for evaluating suspected hoffa fat pad syndrome
  • Findings[14]
    • 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[18]
    • 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

Ultrasound

  • Findings
    • Enlargement and/or decreased echogenicity within the IPFP
    • Color doppler: increased vascularity suggesting inflammation
  • Dynamic ultrasound during knee flexion
    • Can demonstrate impingement of fat pad during terminal extension not visible on static imaging[19]
    • Useful to evaluate suspected herniating IFP (see in flexion, absent in extension)
  • Color Doppler can show[20]
    • Vascularity
    • Sonoelastography

Classification

  • None

Management

Taping for hoffa fat pad syndrome
A) The participant assumes a seated position to flex the knee joint by 90°. The ultrasound probe is placed inferiorly and laterally to the patella to visualise the infrapatellar fat pad. The needle is inserted beneath the ultrasound probe. (B) Ultrasound image for the localisation of the infrapatellar fat pad. Infrapatellar fat pad injection, the needle will be placed in the Hoffa fat pad; intra-articular injection, the needle will go through the Hoffa fat pad into the joint cavity.[21]

Nonoperative

  • Indications
    • First line therapy in all cases
  • Relative rest
  • NSAIDS
  • Brace
  • Ice Therapy
  • Physical Therapy[12]
    • Passive taping to unload or shorten the inflamed fat pad
    • Closed-chain quadriceps exercises to improve lower limb control and patellar congruence
    • Gluteus medius strengthening, anterior hip stretching to decrease internal rotation of the hip and valgus force at the knee
    • Gait training, avoiding hyperextension for long-term management

Procedures

  • Corticosteroid Injections
    • Have shown success with or without ultrasound guidance<[12]
  • Fat Pad Sclerosis and Ablation[22]
    • 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

Operative

  • Indications
    • Failure of conservative measures
  • Technique
    • Arthroscopic resection of IFP
    • Repair of lateral retinaculum (for herniating IFP)
    • Arthroscopic debridement for IFP fibrosis causing extension block after ACL reconstruction
    • Arthroscopic anterior interval release for pain associated with anterior interval scarring
    • Arthroscopic resection of infrapatellar plicae
    • Denervation of the inferior pole of the patella

Rehab and Return to Play

Rehabilitation

  • Phase I[23]
    • Emphasis on pain modulation and inflammation control
    • NSAIDs and topical cold therapy to reduce inflammation
    • Restoration of range of motion
    • Activity modification to avoid aggravating movements (particularly hyperextension)
    • Gait training to normalize movement patterns
    • Passive taping techniques are employed to unload or shorten the inflamed fat pad
  • Phase II[24]
    • Closed-chain quadriceps exercises to improve lower limb control and patellar congruence
    • Gluteus medius strengthening and anterior hip stretching
    • Progressive flexibility training and proprioception retraining
    • Appropriate cardiovascular conditioning
    • Patients should demonstrate full range of motion and normal gait pattern before advancing to this phase
  • Phase III[25]
    • Incorporates sport-specific functional progression
    • Sport-specific assessment and training that serves as the basis for return to prior activity level
    • restore function of the injured part while promoting overall musculoskeletal and cardiovascular function

Patient Handout PDFs

Return to Play

  • Return to play criteria
    • Anatomical and functional healing
    • Restoration of sport-specific skills
    • Psychosocial readiness
    • Ability to perform safely with any necessary equipment modifications, bracing, or orthoses
    • Compliance with applicable regulations
    • Confirmation that the athlete poses no undue risk to other participant

Prognosis and Complications

Knee Osteoarthritis

Prognosis

  • General[26]
    • 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
  • Nonoperative management
    • Genin et al review of case reports: 10/14 patients required surgical intervention after unsuccessful nonoperative management[26]
    • Larbi et al describes successfully treating 4/5 patients with nonoperative management[27]
  • Surgical management
    • Kumar et al described outcomes of 34 patients treated with arthroscopic resection[28]
      • 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[29]
      • there were statistically significant improvement in functional scores and Cincinnati Rating System

Complications

  • Arthrofibrosis[30]
    • Anterior interval scarring, infrapatellar contracture syndrome
    • Chronic fibrosis
    • Osteochondroma formation
  • Chronic knee pain
  • Inability to return to sport
  • Knee Osteoarthritis

See Also

Internal

External

References

  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. ↑ 2.0 2.1 Wang, Magnolia G., Patrick Seale, and David Furman. "The infrapatellar fat pad in inflammaging, knee joint health, and osteoarthritis." npj Aging 10.1 (2024): 34.
  3. ↑ Kumar, Deepak, Abtin Alvand, and J. P. Beacon. "Impingement of infrapatellar fat pad (Hoffa’s disease): results of high-portal arthroscopic resection." Arthroscopy: The Journal of Arthroscopic & Related Surgery 23.11 (2007): 1180-1186.
  4. ↑ Larbi, A., et al. "Hoffa's disease: a report on 5 cases." Diagnostic and interventional imaging 95.11 (2014): 1079-1084.
  5. ↑ Eymard, Florent, and Xavier Chevalier. "Inflammation of the infrapatellar fat pad." Joint Bone Spine 83.4 (2016): 389-393.
  6. ↑ Wang, Chao‐Ying, et al. "Change in T2* relaxation time of Hoffa fat pad correlates with histologic change in a rat anterior cruciate ligament transection model." Journal of Orthopaedic Research 33.9 (2015): 1348-1355.
  7. ↑ Saddik, D., E. G. McNally, and M. Richardson. "MRI of Hoffa’s fat pad." Skeletal radiology 33.8 (2004): 433-444.
  8. ↑ 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
  9. ↑ Gallagher J et al. The infrapatellar fat pad : anatomy and clinical correlations. Knee Surg Sports Traumatol Arthrosc 2005 ; 13 : 268-272.
  10. ↑ 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.
  11. ↑ Genin, Jason, et al. "Infrapatellar fat pad impingement: a systematic review." The Journal of Knee Surgery 30.07 (2017): 639-646.
  12. ↑ 12.0 12.1 12.2 Dragoo, Jason L., Christina Johnson, and Jenny McConnell. "Evaluation and treatment of disorders of the infrapatellar fat pad." Sports medicine 42.1 (2012): 51-67.
  13. ↑ 13.0 13.1 Emad, Y., and Y. Ragab. "Liposynovitis prepatellaris in athletic runner (Hoffa's syndrome): case report and review of the literature." Clinical rheumatology 26.7 (2007): 1201-1203.
  14. ↑ 14.0 14.1 von Engelhardt, Lars Victor, et al. "Hoffa’s fat pad impingement treated arthroscopically: related findings on preoperative MRI in a case series of 62 patients." Archives of orthopaedic and trauma surgery 130.8 (2010): 1041-1051.
  15. ↑ Karkucak, Murat, et al. "Function of the infrapatellar fat pad and advanced Hoffa's disease with ossification." Archives of Rheumatology 29.2 (2014).
  16. ↑ Jarraya, Mohamed, et al. "MRI findings consistent with peripatellar fat pad impingement: How much related to patellofemoral maltracking?." Magnetic Resonance in Medical Sciences 17.3 (2018): 195-202.
  17. ↑ Helpert, C., et al. "Differential diagnosis of tumours and tumour-like lesions of the infrapatellar (Hoffa’s) fat pad: pictorial review with an emphasis on MR imaging." European radiology 14.12 (2004): 2337-2346.
  18. ↑ 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
  19. ↑ Chauvin, Nancy A., et al. "Imaging findings of Hoffa’s fat pad herniation." Pediatric radiology 46.4 (2016): 508-512.
  20. ↑ Vera-Pérez, Erika, et al. "Sonographic characterization of Hoffa’s fat pad. A pilot study." Rheumatology international 37.5 (2017): 757-764.
  21. ↑ Chen, Yiwei, et al. "Comparison of the effectiveness of intra-infrapatellar fat pad and intra-articular glucocorticoid injection in knee osteoarthritis patients with Hoffa’s synovitis: protocol for a multicentre randomised controlled trial." BMJ open 15.1 (2025): e087785.
  22. ↑ House CV, Connell DA. Therapeutic ablation of the infrapatellar fat pad under ultrasound guidance: a pilot study. Clin Radiol 2007;62(12):1198–1201
  23. ↑ Gürsoy, Siddik Göksel, et al. "Evaluation of the relationship between Hoffa volume and radiological and clinical scoring in the diagnosis and treatment of anterior knee pain: A retrospective observational study." Medicine 104.27 (2025): e43244.
  24. ↑ De Carlo, Mark, and Brain Armstrong. "Rehabilitation of the knee following sports injury." Clinics in sports medicine 29.1 (2010): 81-106.
  25. ↑ Herring, Stanley A. "The team physician and return-to-play issues: a consensus statement." Medicine & Science in Sports & Exercise 34.7 (2002): 1212-1214.
  26. ↑ 26.0 26.1 Genin, Jason, et al. "Infrapatellar fat pad impingement: a systematic review." The journal of knee surgery 30.07 (2017): 639-646.
  27. ↑ Larbi A, Cyteval C, Hamoui M, et al. Hoffa’s disease: a report on 5 cases. Diagn Interv Imaging 2014;95(11):1079–1084
  28. ↑ 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
  29. ↑ Ogilvie-Harris DJ, Giddens J. Hoffa’s disease: arthroscopic resection of the infrapatellar fat pad. Arthroscopy 1994;10(02):184–187
  30. ↑ Eymard, Florent, and Xavier Chevalier. "Inflammation of the infrapatellar fat pad." Joint Bone Spine 83.4 (2016): 389-393.
Created by:
John Kiel on 7 July 2019 05:30:07
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7 May 2026 17:33:07
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