Patellofemoral Joint Pain vs Fat Pad Irritation: How to Tell the Difference (and When to Scan)
- Emma Glynn
- 17 hours ago
- 4 min read
By Emma Glynn - APA Titled MSK Physio
The Hip & Knee Physio
This article provides general information only. It is not personal medical advice
Front of knee pain isn’t one diagnosis
If your knee hurts when walking downstairs, sitting for too long, or standing with a locked knee - it could be one of several things (1).
Two of the most common culprits are patellofemoral pain (PFP) and fat pad irritation. They’re often confused, and while they can sometimes overlap, understanding the difference helps avoid unnecessary scans, overcautious rest, or the wrong kind of rehab (2).
Here’s how to tell them apart and when it’s worth getting your knee assessed.
Quick Way to Spot the Difference
Where it hurts
Patellofemoral pain: Vague ache around or behind the kneecap. Often feels like a diffuse “circle” under the patella, not sharp or localised (1).
Fat pad irritation (also called Hoffa’s fat pad impingement): Sharp or pin point pain just below the kneecap, toward the bottom front of the joint. Often very sensitive to touch (2).
What provokes it
Patellofemoral pain:
Walking or running downstairs
Deep squats or lunges
Long periods of sitting (e.g. in the car or at the movies)
Hills or inclines (3)
Fat pad irritation:
Standing or walking with a locked (fully straight) knee
Landing on a straight leg or hyperextending during sport
Kneeling or direct pressure just below the kneecap (3)
What eases it short-term
Patellofemoral pain:
Taking smaller steps on stairs
Slowing pace
Knee cap taping (McConnell-style) to improve alignment or reduce load (1)
Fat pad irritation:
Avoiding locked knee positions when standing
Soft knee landings or micro-bend during walking
Taping to unload the fat pad or using a small heel lift in your shoe temporarily (3)
Why Going Downstairs Hurts More
Walking downstairs increases load through the kneecap joint. In fact, the patellofemoral joint force can be over 3x bodyweight during descent, especially with speed, long strides, or a forward-leaning posture (2).
This is why technique (e.g., small steps, upright torso) and control matter as much as strength. Pain doesn’t always relfect damage, it can mean the joint is not tolerating the load at the time (1).
Sitting Pain (“Movie-Theatre Sign”)
If your knee aches after long periods of sitting, especially with knees bent, this points more toward patellofemoral pain (3).
When the knee is flexed, the kneecap presses against the femur, which can irritate a sensitive joint. This often improves with:
Briefly straightening the leg
Changing position
Moving after inactivity (3).
This is not dangerous but it’s a sign your joint is asking for a change in load or position.
When (and When Not) to Scan
Most people with classic patellofemoral or fat pad symptoms don’t need scans straight away. Both conditions are diagnosed clinically based on:
Symptom location
Aggravating movements
Physical examination
You might consider imaging if:
You’ve had recent trauma (e.g., a fall, twist, or landing incident)
There’s true locking or giving way
You’re not improving after several weeks of targeted treatment
There’s suspicion of intra-articular pathology beyond the front of knee tissues (3).
Scans can rule out structural injury, but they’re not always helpful early on. Many people with “abnormal” MRIs don’t have symptoms and vice versa (2).
What Usually Helps
While treatment needs to be tailored, here’s what evidence supports for both conditions:
Education on pain vs damage, load tolerance, and aggravators (1).
Technique tweaks:
Smaller steps on stairs
Controlled descent
Avoiding locked knees when standing
Strengthening:
Glutes, quads, and calves all play a role in shock absorption and knee control (3)
Short-term adjuncts:
Taping (McConnell for PFP, offloading tape for fat pad)
Soft sleeves or temporary heel lifts (for fat pad)
Addressing overstriding or cadence issues in runners (3)
If you’re not sure what’s right for your knee, book with a knee physiotherapist in Camberwell for a targeted assessment.
When to Get Help
If your front of knee pain is:
Getting worse
Affecting sleep
Limiting your ability to walk, squat, or exercise, even after simple changes…it’s worth getting assessed. A physio can help you identify the root cause, manage flare-ups, and build a plan forward.
You Don’t Have to Guess
Front of knee pain is one of the most common presentations in active adults over 45 and it’s usually very manageable with the right strategy.
Want help figuring out whether it’s patellofemoral pain or fat pad irritation?
👉 Have questions about your symptoms? Get in touch on 03 9978 9833
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References
Barton CJ, Lack S, Hemmings S, et al. Best Practice Guide to Conservative Management of Patellofemoral Pain. Br J Sports Med. 2015;49(14):844–852.
Crossley KM, et al. 2016 Patellofemoral Pain Consensus Statement. Br J Sports Med. 2016;50(14):842–852.
Willy RW, et al. Patellofemoral pain: clinical practice guidelines linked to the International Classification of Functioning, Disability, and Health. J Orthop Sports Phys Ther. 2019;49(9):CPG1–CPG95.
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