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Health condition · Clinically reviewed

Fat pad impingement, the overlooked cause of anterior knee pain.

Hoffa’s fat pad is small, richly innervated and sits right at the front of your knee. Get the diagnosis right and a stepped plan settles most cases.

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A radiographer guides a patient onto the bed of an advanced 3 Tesla MRI scanner in a London imaging suite

Why trust this guide

  • 01

    Clinically reviewed

    Written by our editorial team and reviewed by a registered UK clinician before publication.

  • 02

    Sourced from guidance

    Checked against BASEM, BOA and peer-reviewed musculoskeletal sources you can see at the end.

  • 03

    Current for 2026

    Reflects modern UK sports medicine and orthopaedic practice, including ultrasound-guided injection care.

Key facts

Fat pad impingement at a glance.

The essentials, in plain English – what it is, why it hurts and how it is treated in the UK today.

  • What it is

    Inflammation and entrapment of the infrapatellar fat pad (Hoffa’s fat pad), a richly innervated cushion between the patella and patellar tendon.

  • Also called

    Hoffa syndrome, Hoffa’s fat pad impingement or infrapatellar fat pad syndrome.

  • Why it hurts

    The fat pad is packed with nerve endings and blood vessels, so once irritated it becomes one of the most pain-sensitive tissues in the knee.

  • Common trigger

    Hyperextension or direct blow to the front of the knee, or chronic microtrauma from running, jumping and prolonged standing.

  • Often missed

    Frequently mislabelled as patellofemoral pain or patellar tendinopathy, delaying the right rehab plan.

  • Foundation therapy

    Relative rest, hyperextension avoidance, targeted quadriceps rehab and, where needed, an ultrasound-guided corticosteroid injection.

Why this guide matters

A stepped plan, not another injection.

Fat pad impingement responds to careful assessment and the right ladder of care. Three principles shape the rest of this page.

  • Get the diagnosis right

    Anterior knee pain is not one thing. Distinguishing fat pad impingement from patellofemoral pain and patellar tendinopathy changes the plan.

  • Rehab is the workhorse

    Targeted quadriceps strengthening, hamstring flexibility and hyperextension-avoidance training carry most people to a good outcome.

  • Escalate calmly, not quickly

    When rehab has stalled, an ultrasound-guided injection is a good next step. Surgery is a last resort, not a first move.

How the diagnosis is made

From first twinge to a clear plan.

The steps a UK GP, sports physician or specialist physiotherapist will normally follow, in order.

  1. 01

    Assessing

    Focused history

    Anterior knee pain below the kneecap, worse with straightening the knee, standing tall, walking downhill or long periods on your feet.

  2. 02

    Assessing

    Look and palpate

    Swelling below the patella and either side of the patellar tendon, with tenderness on direct pressure over the fat pad.

  3. 03

    Assessing

    Hoffa’s test

    Thumbs press either side of the patellar tendon while the knee is extended from flexion. Sharp anterior pain is a positive test.

  4. 04

    Confirming

    Hyperextension test

    Passive knee hyperextension reproduces the pain and often the sense of pinching that patients describe.

  5. 05

    Confirming

    Rule out mimics

    Careful examination to exclude patellofemoral pain, patellar tendinopathy, meniscal injury, plica syndrome and early osteoarthritis.

  6. 06

    Preparing

    MRI where needed

    Specialist musculoskeletal MRI can show fat pad oedema, fluid and fibrosis (Hoffa’s disease) and confirm the diagnosis in stubborn cases.

  7. 07

    Preparing

    Specialist review

    Sports and exercise medicine, orthopaedics or specialist physiotherapy input shapes a stepped plan.

Typical timeline: a first visit to a settled plan in weeks, not months.

Symptoms

What fat pad impingement feels like.

Sharp anterior knee pain, worse when the knee is straightened, with tenderness either side of the patellar tendon. If it sounds familiar, read on.

  • Anterior knee pain

    Aching or sharp pain at the front of the knee, sitting just below the kneecap on one or both sides of the patellar tendon.

  • Worse with hyperextension

    Standing tall, walking downhill and prolonged standing all straighten the knee fully and reproduce the pain.

  • Local swelling

    Puffiness sitting below the patella and either side of the patellar tendon, sometimes described as “fullness” rather than a joint swelling.

  • Tenderness on palpation

    Direct pressure over the fat pad on either side of the tendon is uncomfortable, and often much more tender than the tendon itself.

  • Positive Hoffa’s test

    Pain reproduced when the examiner presses the fat pad and the knee is straightened from a bent position.

  • Quadriceps weakness

    Reflex inhibition of the quadriceps, particularly the vastus medialis, leaves the knee feeling weak and unstable.

  • Post-surgical onset

    New anterior knee pain after arthroscopy or knee replacement is a classic presentation and easily overlooked.

  • Red flag — locking or giving way

    Mechanical locking, true instability or a large effusion points to another intra-articular problem needing prompt review.

Treatment

How fat pad impingement is treated in the UK.

Load management and rehab first, an ultrasound-guided injection when needed, and arthroscopic partial resection only as a last resort.

  • Relative rest

    Short-term reduction in aggravating loads. Avoid hyperextension, prolonged standing and downhill walking while the fat pad calms.

  • Activity modification

    Shorten stride, avoid locking the knee out and swap downhill running for flatter routes or cycling while symptoms settle.

  • Simple analgesia

    Ice, topical NSAIDs and short-course oral NSAIDs where appropriate for symptom control alongside rehab.

  • Specialist physiotherapy

    Quadriceps strengthening with a focus on the vastus medialis, hamstring flexibility, gait retraining and hyperextension-avoidance drills.

  • Taping and bracing

    McConnell taping to unload the fat pad, or a bespoke brace, gives short-term relief while rehab does the heavier lifting.

  • Heel lifts

    Small heel raises can reduce end-range knee extension and give the fat pad a rest during standing and walking.

  • Ultrasound-guided injection

    A targeted corticosteroid injection under ultrasound guidance is often effective when conservative care has stalled. See the cortisone injection guide below.

  • Arthroscopic resection

    Partial arthroscopic resection of the fat pad is a last-resort specialist option for the small number of patients who do not settle.

Not sure whether you have fat pad impingement or something else? Our guide to patellofemoral pain syndrome covers the closest mimic.

What this guide is based on

The sources behind every claim on this page.

UK sports medicine and orthopaedic guidance, alongside peer-reviewed musculoskeletal literature current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

A GP, sports physician or specialist physiotherapist can examine your knee and tell you which parts of this guide apply to you.

  • British Association of Sport and Exercise Medicine (BASEM). Anterior knee pain resources.

  • British Orthopaedic Association (BOA). Knee pain assessment standards.

  • NHS. Knee pain: assessment and management.

  • Peer-reviewed musculoskeletal literature on Hoffa’s fat pad syndrome and infrapatellar impingement.

Red flags

When knee pain needs urgent attention.

Most anterior knee pain is manageable in primary care or with a specialist physiotherapist. These are the features that change the picture.

  • True locking of the knee

    A knee that catches or locks and will not straighten suggests a meniscal or loose body problem, not fat pad impingement alone.

  • Large tense effusion

    A hot, swollen, tense knee needs urgent review to rule out haemarthrosis, septic arthritis or crystal disease.

  • Systemic features

    Fever, night sweats, weight loss or feeling generally unwell alongside knee pain warrant urgent medical assessment.

  • Significant trauma

    A high-energy injury with an audible pop, immediate swelling or inability to weight bear needs same-day orthopaedic review.

  • Neurological change

    New numbness, weakness or foot drop below the knee is not fat pad impingement and needs prompt review.

  • Post-operative concerns

    New severe pain, spreading redness or fever after knee surgery is a surgical emergency until proven otherwise.

  • Suspected fracture

    Bony tenderness after a fall, especially in older patients, needs an X-ray before rehab is started.

  • Progressive night pain

    Relentless night pain unresponsive to rest and simple analgesia deserves a specialist opinion.

  • Uncontrolled pain despite rehab

    Persistent disabling pain after 8 to 12 weeks of well-run conservative care is a signal to escalate, not to push harder.

Living with it

A treatable problem, with a clear ladder.

Four practical shifts that make the biggest difference day to day – posture, load, strength and knowing when to escalate.

A quiet reminder

Consistency beats intensity, every time.

A steady rehab programme, done properly for a few months, outperforms a heroic fortnight that never gets repeated.

  1. 01 Position

    Break the hyperextension habit

    Standing with knees locked back is a common trigger. A gentle soft-knee stance takes pressure off the fat pad throughout the day.

  2. 02 Load

    Trade the downhills

    Downhill walking and running load the fat pad hard. Swap for flatter routes or cycling while things settle, then reintroduce gradually.

  3. 03 Strength

    Build the quads properly

    A targeted quadriceps programme, guided by a specialist physiotherapist, is the single most useful long-term intervention.

  4. 04 Escalate

    Know when to ask for more

    If 8 to 12 weeks of good rehab has not shifted things, an ultrasound-guided injection or specialist review is a reasonable next step.

Frequently asked

Everything we get asked about fat pad impingement.

Quick answers on diagnosis, imaging, rehab, injections and when surgery matters.

  • What is fat pad impingement?

    Fat pad impingement, also called Hoffa syndrome or infrapatellar fat pad syndrome, is inflammation and entrapment of the infrapatellar fat pad. This richly innervated cushion sits between the kneecap and the patellar tendon and, when irritated, becomes a major source of anterior knee pain.

  • Why is it often confused with other knee problems?

    The anterior knee has several pain generators sitting close together, including the patellofemoral joint, the patellar tendon, the plica and the fat pad itself. Careful examination, in particular Hoffa’s test and the hyperextension test, and specialist musculoskeletal imaging where needed, help distinguish fat pad impingement from patellofemoral pain and patellar tendinopathy.

  • What makes it worse?

    Anything that fully straightens or hyperextends the knee tends to aggravate the fat pad. Common triggers include standing tall for long periods, walking downhill, wearing very flat shoes, and activities that involve repeated hyperextension such as running and jumping.

  • Do I need an MRI?

    Not always. Many people are diagnosed clinically, with a good history and a positive Hoffa’s or hyperextension test. A specialist musculoskeletal MRI is helpful when the diagnosis is unclear, symptoms are stubborn, or a specialist is considering an injection or surgery.

  • Do injections work?

    For patients who have not settled with rehab, an ultrasound-guided corticosteroid injection into the fat pad is often effective and is a well-established next step. It works best when combined with a structured physiotherapy programme rather than used in isolation.

  • Will I need surgery?

    Very rarely. The great majority of people improve with a stepped plan of activity modification, physiotherapy and, where needed, an injection. Arthroscopic partial fat pad resection is reserved for the small number of patients who remain limited after high-quality conservative care.

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