What Is Prepatellar Bursitis (Housemaid's Knee)?
Prepatellar bursitis is swelling of the small fluid-filled sac (bursa) that sits directly over the front of your kneecap. It is often called housemaid's knee because it is common in people who kneel for long periods. The swelling can range from mild puffiness to a noticeable, tender lump that makes kneeling painful.
Key points
- The prepatellar bursa cushions the kneecap. Repeated pressure or a direct blow can irritate it and cause fluid to build up.
- A hot, red, swollen knee may be infected (septic bursitis) and needs urgent medical attention.
- Scans taken lying down can miss alignment problems that increase pressure on the front of the knee when you stand and walk.
- Prepatellar bursitis is one of several types of bursitis that can affect the knee.
- ScanAlign uses EOS standing imaging to show how your whole leg takes load under your own body weight.
Your prepatellar bursa is a thin, fluid-filled cushion between the skin and the kneecap (patella). Normally you would not know it is there. Its job is to reduce friction, so the skin can glide smoothly when you bend and straighten your knee.
When this bursa becomes irritated, it fills with extra fluid and swells up. That is prepatellar bursitis. It is one of the most common forms of knee bursitis, along with infrapatellar bursitis (just below the kneecap) and pes anserine bursitis (on the inner side of the shin).
What does prepatellar bursitis feel like?
The main sign is a soft, sometimes warm swelling directly over the front of your kneecap. It can appear slowly after weeks of kneeling, or quickly after a knock or fall.
A puffy or egg-shaped lump sitting right on top of the kneecap. It may feel spongy when pressed.
Kneeling or pressing directly on the knee is uncomfortable or painful. Walking on a flat surface may feel normal.
A feeling of tightness at the front of the knee, especially when you bend it fully.
The skin over the swelling may feel warmer than the skin around it.
What causes swelling in front of the kneecap?
Repeated pressure on the prepatellar bursa is the most common cause. The bursa becomes irritated and inflamed, and fills with extra fluid. Several things can trigger this.
Carpet layers, plumbers, gardeners, cleaners. Any job or hobby that keeps you on your knees for hours.
A fall onto the knee or a blow during sport can cause sudden swelling.
A cut or graze near the knee can let bacteria into the bursa, causing septic bursitis. This is a medical emergency.
Gout or rheumatoid arthritis can sometimes inflame the bursa without direct pressure.
When is knee swelling a sign of something serious?
Most prepatellar bursitis is not dangerous, but an infected bursa (septic bursitis) needs urgent treatment. Look out for the combination of symptoms below.
Get urgent medical attention (see your doctor or go to the emergency department) if you notice:
- The knee is very red, hot and swollen, and redness is spreading beyond the kneecap
- You develop a fever, chills, or feel generally unwell
- There is an open wound near the swelling
- The pain is severe and getting worse quickly
These can be signs of septic bursitis or another infection. Do not wait for a scan appointment. Get medical help straight away.
How is prepatellar bursitis diagnosed?
A doctor can usually diagnose prepatellar bursitis by examining your knee and asking about your activities. In some cases, further imaging helps rule out other problems, such as a fracture or a deeper joint problem. If infection is suspected, fluid may be drawn from the bursa (aspiration) and tested.
When is MRI the better choice? EOS standing imaging is excellent for showing bones, joints and overall leg alignment. For soft-tissue detail, such as the bursa itself, the tendons around it, or ligament damage, MRI is usually the better tool. Your treating specialist can advise which you need.
Why does standing alignment matter for knee bursitis?
Alignment problems in the leg can change the way forces pass through your knee. If your leg is slightly rotated, or you have a knock-knee or bow-leg pattern, extra pressure may fall on the front of the kneecap every time you kneel or bend.
Standard scans are usually taken lying down. When you lie flat, your muscles relax and your joints settle into a position that does not reflect how they work in daily life. Problems that only appear under load, when you are standing and bearing weight, can be missed entirely.
Your body is a connected chain, from your feet through your knees, hips and spine. A slight tilt in the pelvis or a rotation in the shin can shift load onto the front of the kneecap. You feel the problem at the knee, but the cause may be above or below it. Standing whole-body imaging captures the full picture, so your treating specialist can see exactly where the imbalance starts.
EOS imaging uses about 90% less radiation than a standard X-ray, around ten times less. You simply stand still inside the scanner for a few seconds while it captures your full lower limb alignment in one pass.
Before you start treatment, or change the one you are on, it is worth getting a detailed diagnosis. Knowing whether the cause sits in the pelvis, the legs or the spine changes what will actually help.
If your knee bursitis keeps coming back, alignment may be part of the picture. A standing assessment can help your treating specialist understand why.
Book a free video consultationWhat helps with prepatellar bursitis?
Treatment depends on the cause and how severe it is. ScanAlign is a diagnostic imaging clinic and does not provide treatment, but we can share what is generally recommended.
- Avoid the trigger. If kneeling caused the problem, kneeling less or stopping gives the bursa time to settle. Knee pads or a cushioned mat can help if you must kneel.
- Change your activity. Rest, ice, and keeping the knee raised can reduce swelling in mild cases.
- Medical review. Your doctor or a specialist may recommend anti-inflammatory medicine, aspiration (draining the fluid), or further tests if the swelling keeps coming back.
- Alignment assessment. For bursitis that keeps returning, understanding how your leg takes load under body weight can help identify contributing factors that simple rest does not address.
You can book a knee assessment to see whether standing alignment is contributing to ongoing or recurring symptoms.
Frequently asked questions about prepatellar bursitis
Yes. Housemaid's knee is the common name for prepatellar bursitis. It was first linked with domestic workers who spent hours kneeling to scrub floors.
Mild cases often improve within a few weeks once the activity that aggravates it is stopped. Long-term or recurring cases can take longer and may need medical treatment such as aspiration, or further tests.
It depends on how severe it is. Activities that do not put direct pressure on the kneecap, such as swimming or cycling, are usually better tolerated. Avoid kneeling, squatting, or any exercise that puts the front of the knee under load until your symptoms settle.
Signs of infection include marked redness and warmth spreading beyond the kneecap, fever, chills, and pain that gets worse quickly. If you notice these, get urgent medical attention from your doctor or the emergency department.
They involve different bursae. The prepatellar bursa sits over the top of the kneecap, while the infrapatellar bursa sits just below it. Both can be irritated by kneeling, but the exact place of the swelling and tenderness differs slightly.
No. ScanAlign is a private, self-pay clinic. You do not need a referral from your doctor. You can book a free video consultation directly to discuss whether imaging is right for your situation.
Yes. EOS uses about 90% less radiation than a standard X-ray, around ten times less. It is a very low-dose imaging system designed for standing, weight-bearing assessments.
The price for patients travelling from abroad is confirmed during the free video consultation.
Possibly. If your leg alignment puts extra stress on the front of the knee, the bursa may become irritated again and again, even after treatment. Standing imaging can reveal these patterns so your treating specialist can address the underlying cause.
You stand naturally inside the EOS scanner while it captures images of both legs in full. The scan takes only a few seconds and is painless. You receive a detailed report that your treating specialist can use to plan the next steps.
Knee swelling that keeps coming back?
A free video consultation can help you understand whether standing alignment imaging in London is the right next step for you.
Book a free video consultationAuthor: Abbas Dhami (Specialist Diagnostic Radiographer)
Sources
- NHS. "Bursitis." nhs.uk. Accessed 2024.
- Rishor-Olney CR, Pozun A. "Prepatellar Bursitis." StatPearls, National Library of Medicine, 2023.
- American Academy of Orthopaedic Surgeons (AAOS). "Prepatellar (Kneecap) Bursitis." OrthoInfo. Accessed 2024.
This page is general information and not a diagnosis.
ScanAlign is the trading name of CoreMed Solutions Ltd and operates under The Harley Street Hospital's CQC licence.