You have been on your knees all week, laying tiles, fitting a floor, weeding the garden or crawling after a toddler, and now there is a soft, squishy lump the size of an egg sitting right on top of your kneecap. It is not sore inside the knee, the knee still bends, but the swelling is obvious and kneeling on it is out of the question.
That is almost certainly prepatellar bursitis, the swelling of the small fluid-filled sac that sits between the kneecap and the skin. Tradies know it well, even if they have never heard the name. Most cases settle once the kneeling stops. A minority are infected, and telling the two apart is the most important thing this article will teach you.
In this article
What is prepatellar bursitis?
A bursa is a thin, slippery sac of fluid that sits between bone and the tissues that slide over it, reducing friction. The prepatellar bursa sits directly in front of the kneecap, just under the skin. Repetitive pressure and friction, which is what kneeling is, irritate its lining and it produces excess fluid. The result is a visible, often painless or mildly tender swelling on the front of the knee. A single direct blow to the kneecap can do the same thing more quickly.
The old name, housemaid's knee, dates from an era of scrubbing floors by hand. Today it is the tiler's, carpet-layer's, plumber's, roofer's and gardener's knee, and it also turns up in wrestlers, volleyballers and anyone who has taken a fall onto a hard surface.
How do I know it is not inside the knee joint?
Location and movement. Prepatellar bursitis sits on top of the kneecap, so the swelling is a distinct, mobile lump you can often shift slightly with your fingers, and the knee usually still bends and straightens fully, if a little tightly, because the joint itself is not swollen. Fluid inside the joint, by contrast, sits around and below the kneecap, makes the whole knee feel full and stiff, and limits bending. Pain from the joint line, locking or giving way point to a different problem.
If you are not sure which you have, our physio in Mount Gravatt team can tell the difference in a few minutes and check the rest of the knee while they are at it.
Who gets it, and how many are infected?
Who it affects
The same review reports a minimum annual incidence of 10 per 100,000, with about 80% of cases in men and a peak between the ages of 40 and 60, matching the kneeling trades that drive it.
That one-in-three figure is why prepatellar bursitis deserves more respect than a "just a bit of fluid" shrug. Because the bursa sits right under the skin, a scrape, a splinter or a crack in the skin over the kneecap gives bacteria a short route in.
Egg on the kneecap? A physiotherapy assessment at ACE Sports Medicine in Upper Mount Gravatt can confirm what it is, rule out the joint, and plan how to settle it.
Settle it or see someone: the infection question
A non-infected bursa is swollen, soft, and mildly tender or painless. The skin over it looks normal or is a little pink from the pressure. You feel well.
An infected bursa is a different picture: increasing pain, warmth and redness spreading over and around the kneecap, the skin looking tight and shiny, sometimes a nearby cut or graze, and often feeling generally unwell or feverish. That combination needs same-day medical review, because a septic bursa is treated with antibiotics and sometimes drainage, and untreated infection can spread. When in doubt, get it looked at the same day.
What actually helps?
Stop the friction. The bursa cannot settle while it is still being knelt on. Take kneeling out of the picture for a period, and where it is unavoidable, use proper knee pads or a kneeling board. This alone resolves many early cases.
Compress and manage the swelling. A compression sleeve, ice in the early days and elevation when you can help the fluid resolve. Many non-infected cases settle over a number of weeks with this approach.
Address how the knee is loaded. A physiotherapy programme looks at quadriceps and hip strength, how you get down to and up from the floor, and the working positions that put the kneecap under the most pressure, so the problem is less likely to recur when you go back to the tools. For persistent non-infected swelling, aspiration (draining the fluid) and in some cases an injection are options a doctor can discuss, and surgery is uncommon.
When should you seek help?
A soft, painless swelling after a week on your knees that is already shrinking with rest and knee pads can be watched for a short time. Anything else is worth a proper look.
Consider getting assessed if
The swelling has lasted more than a couple of weeks or keeps coming back each time you return to work; it is limiting how far the knee bends; you are unsure whether the fluid is on the kneecap or inside the joint; or it followed a significant fall. Seek same-day medical care if the knee becomes hot, red and increasingly painful, if there is a cut or graze over the swelling, or if you feel unwell or feverish, as these suggest infection.
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Helping You Perform at Your Best
Our physiotherapy team at ACE Sports Medicine in Upper Mount Gravatt assesses and treats knee swelling for people across Brisbane's southside, from the tiler who cannot afford a week off the tools to the gardener who wants to get back on the ground. Prepatellar bursitis often responds well to the right care, and a quick assessment tells you whether it is the simple kind or the same-day kind.