Infrapatellar Fat Pad Impingement

Last updated: February 8, 2026Reviewed date: February 8, 2026Reading time: 5 min read
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Article Summary

Infrapatellar fat pad syndrome is when your fat pad becomes pinched (impinged) between your kneecap and thigh bone, or your thigh and shin bones. It's also known as infrapatellar fat pad impingement. Your infrapatellar fat pad has a rich supply of nerves, so impingement can be very painful. Infrapatellar fat pad impingement can occur for many reasons, including the Overload of the extensor (quadriceps) mechanism such...

Key Takeaways

  • This article explains Other Names in simple medical language.
  • This article explains Pathophysiology in simple medical language.
  • This article explains Causes in simple medical language.
  • This article explains Diagnosis in simple medical language.
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Definition

Infrapatellar fat pad is when your fat pad becomes pinched (impinged) between your and , or your thigh and shin bones. It’s also known as infrapatellar fat pad impingement. Your infrapatellar fat pad has a rich supply of nerves, so impingement can be very painful. Infrapatellar fat pad impingement can occur for many reasons, including the Overload of the extensor (quadriceps) mechanism such as when running and when kicking a ball during football. Hyperextension of the knee (over straightening of the knee), e.g. in gymnastics/dance. Symptoms of fat pad syndrome are anterior knee , often retropatellar and infrapatellar. Patellofemoral crepitus might be present, with knee loading such as in stairs negotiation, squatting, jumping, and running. Effusion and decreased ROM are often seen with inflamed IFP. This is often hard to pinpoint and there has been no clear injury. Activities such as climbing the stairs, or even sitting with the knee bent are painful. In some cases, there is a background ache and occasional jolts of sharp pain. Treatment for Hoffa’s fat pad syndrome involves reducing and controlling nerve pinching in your knees. The first line of treatment involves rest and medications. Other conservative treatments include taping the knee, performing strengthening exercises, and injections.

Other Names

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

Pathophysiology

  • General
    • The disease process suffers from a paucity of literature
    • The IFP is an intracapsular, extra synovial adipose tissue structure in the anterior knee
    • An important source of anterior knee pain

Causes

  • 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 impinges between the  and Medial Femoral Condyle
  • Alternatively may impinge between the and during extension
  • This leads to inflammation, , inflammation with necrosis, and
  • Pathology is thought to be caused due to
    • Inflammation and fibrosis associated with
    • Trauma may be a direct blow, hyperextension, chronic irritation or postsurgical scarring
  • Pediatric population
    • IFP can herniate through a defect in the lateral retinaculum
    • Will present as a painless, atraumatic mass in the anterolateral infrapatellar region
  • Infrapatellar Fat Pad
    • Intracapsular and intrasynovial 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
  • Borders
    • Anterior: Patellar Tendon,
    • Superior: the inferior pole of the Patella
    • Inferior: proximal Tibia, deep infrapatellar , intermeniscal , meniscal horns and infrapatellar bursa
    • Posterior: joint , femoral condyles, and intercondylar notch.
  • Attachments
    • intercondylar notch via the ligamentum mucosum
    • Anterior horns of the
    • The 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
    • The horizontal cleft in the posteroinferior aspect of the fat pad
  • Vascular Supply
    • Upper and lower geniculate create an abundant peripheral anastomotic blood supply
    • Supromedial and superolateral geniculate arteries provide 2 vertical arteries
    • 2 or 3 horizontal arteries connect the vertical arteries
  • Innervation
    • The predominant nerve supply to the fat pad is the Posterior Tibial Nerve
  • Female > Male (need citation)
  • Sports that require a forceful extension of the knee
    • Dance
    • Gymnastics
    • Swimming
    • Martial arts
    • Jumping events (high jump, long jump, triple jump)

  • Fractures
    • Distal Femur
    • Patellar Fracture
    • Tibial Plateau Fracture
  • Dislocations & Subluxations
    • Patellar  (and subluxation)
    • Knee Dislocation
    • Proximal Tibiofibular
  • Muscle and Tendon Injuries
    • Quadriceps Contusion
    • Iliotibial Band Syndrome
    • Quadriceps
    • Patellar Tendonitis
    • Popliteus
    • Extensor Mechanism Injury
      • Patellar Tendon Rupture
      • Quadriceps Tendon Rupture
      • Patellar Fracture
  • Ligament Pathology
    • ACL Injury
    • PCL Injury
    • MCL Injury
    • LCL Injury
    • Meniscal Pathology
    • Posterolateral Corner Injury
    • Multiligament Injury
  • Arthropathies
    • Knee
    • Septic Arthritis
    • Gout
  • Bursopathies
    • Prepatellar Bursitis
    • Pes Anserine Bursitis
    • MCL Bursitis
    • Infrapatellar Bursitis
  • Patellofemoral Pain Syndrome (PFPS)/ Anterior Knee Pain)
    • Chondromalacia Patellae
    • Patellofemoral Osteoarthritis
    • Osteochondral Defect Knee
    • Plica Syndrome
    • Infrapatellar Fat Pad Impingement
    • Patellar Instability
  • Neuropathies
    • Saphenous Nerve Entrapment
  • Other
    • Bakers Cyst
    • Patellar Contusion
  • Pediatric Considerations
    • Patellar Apophysitis (Sinding-Larsen-Johansson Disease)
    • Patellar Pole Avulsion Fracture
    • Tibial Tubercle Avulsion Fracture
    • Tibial Tuberosity Apophysitis (Osgood Schalatters Disease)

Diagnosis

  • 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
    • The 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
    • Hoffa’s Test: pain with pressure on the medial or lateral side of the patella with the knee in extension

Radiographs

  • Standard Radiographs Knee
    • May be normal
  • Findings
    • Small effusion
    • Case reports have shown calcifications, opacity

MRI

  • Findings[6]
    • Hypointensity lesions
    • Ossified lesion
    • Solitary unossified lesions
    • Localized edema of the superior and/or posterior part of the infrapatellar fat pad
    • Deep fluid-filled infrapatellar bursa
    • Non visualization of vertical and/or horizontal clefts
    • Fibrosis or calcification of the fat pad
  • Clinical correlation with MRI findings
    • Specific edema locations do not correlate with clinical infrapatellar fat pad impingement
    • Patients with clinical symptoms do have more regions of edema
    • The 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
    • Can demonstrate impingement of fat pad during terminal extension
    • Useful to evaluate suspected herniating IFP (see inflection, absent in extension)

Treatment

Nonoperative

  • Indications
    • First-line therapy in all cases
  • Relative rest
  • NSAIDS
  • 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 bupivacaine 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)

 

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Which doctor may help?

Start with a registered doctor or the nearest qualified health center.

What to tell the doctor

  • Write when the problem started and how it changed.
  • Bring old prescriptions, investigation reports, and current medicines.
  • Write allergies, pregnancy status, diabetes, kidney/liver disease, and major past illnesses.
  • Bring one family member if the patient is weak, elderly, confused, or a child.

Questions to ask

  • What is the most likely cause of my symptoms?
  • Which danger signs mean I should go to hospital quickly?
  • Which tests are necessary now, and which can wait?
  • How should I take medicines safely and what side effects should I watch for?
  • When should I come for follow-up?

Tests to discuss

  • Vital signs: temperature, pulse, blood pressure, oxygen saturation
  • Basic physical examination by a clinician
  • CBC, urine test, blood sugar, or imaging only when clinically needed

Avoid these mistakes

  • Do not use antibiotics, steroid tablets/injections, or strong painkillers without proper medical advice.
  • Do not hide pregnancy, kidney disease, ulcer, allergy, or blood thinner use.
  • Do not delay emergency care when danger signs are present.

Medicine safety and first-aid guide

This section is for patient education only. It does not replace a doctor, pharmacist, or emergency care.

Safe first steps

  • Rest, drink safe water, and observe symptoms carefully.
  • Keep a written note of symptoms, duration, temperature, medicines already taken, and allergy history.
  • Seek medical care quickly if symptoms are severe, worsening, or unusual for the patient.

OTC medicine safety

  • For mild pain or fever, ask a registered pharmacist or doctor before using common over-the-counter pain/fever medicines.
  • Do not combine multiple pain medicines without advice, especially if you have kidney disease, liver disease, stomach ulcer, asthma, pregnancy, or take blood thinners.
  • Do not give adult medicines to children unless a qualified clinician advises it.

Avoid these mistakes

  • Do not start antibiotics without a proper medical decision.
  • Do not use steroid tablets or injections casually for quick relief.
  • Do not delay emergency care because of home remedies.

Get urgent help if

  • Severe symptoms, confusion, fainting, breathing difficulty, chest pain, severe dehydration, or sudden weakness need urgent medical care.
Medicine names, dose, and timing must be decided by a qualified clinician or pharmacist after checking age, pregnancy, allergy, other diseases, and current medicines.

For rural patients and family caregivers

Patient health record and symptom diary

Write your symptoms, medicines already taken, test results, and questions before visiting a doctor. This note stays on your device unless you print or copy it.

Doctor to discuss: Doctor / qualified healthcare provider
Tests to discuss with doctor
  • Basic vital signs: temperature, pulse, blood pressure, oxygen level if needed
  • Relevant blood, urine, imaging, or specialist tests only after clinical assessment
Questions to ask
  • What is the most likely cause of my symptoms?
  • Which warning signs mean I should go to emergency care?
  • Which tests are really needed now?
  • Which medicines are safe for my age, pregnancy status, allergy, kidney/liver/stomach condition, and current medicines?

Emergency warning signs such as chest pain, severe breathing difficulty, sudden weakness, confusion, severe dehydration, major injury, or loss of bladder/bowel control need urgent medical care. Do not wait for online information.

Safe pathway to proper treatment

Care roadmap for: Infrapatellar Fat Pad Impingement

Use this simple roadmap to understand the next safe steps. It is educational and does not replace examination by a doctor.

Go to emergency care if you notice:
  • Severe or rapidly worsening symptoms
  • Breathing difficulty, chest pain, fainting, confusion, severe weakness, major injury, or severe dehydration
Doctor / service to discuss: Qualified healthcare provider; specialist depends on symptoms and examination.
  1. Step 1

    Check danger signs first

    If danger signs are present, seek emergency care and do not wait for online information.

  2. Step 2

    Record the symptom story

    Write when symptoms started, severity, medicines already taken, allergies, pregnancy status, and test results.

  3. Step 3

    Visit a qualified clinician

    A doctor, nurse, or qualified healthcare provider can examine you and decide which tests or treatment are needed.

  4. Step 4

    Do only useful tests

    Do tests after clinical assessment. Avoid unnecessary tests, random antibiotics, or repeated medicines without diagnosis.

  5. Step 5

    Follow up and return early if worse

    If symptoms worsen, new warning signs appear, or treatment is not helping, return for review quickly.

Rural patient practical tips
  • Take a written symptom diary and all previous prescriptions/test reports.
  • Do not hide medicines already taken, even herbal or over-the-counter medicines.
  • Ask which warning signs mean urgent referral to hospital.

This roadmap is for education. A real diagnosis and treatment plan requires history, examination, and clinical judgment.