Home / Conditions / Knee bursitis
A bursa is a small, fluid-filled cushion that lets skin and tendons slide over bone. Knee bursitis is when one of them swells — most often over the kneecap, after a lot of kneeling. It usually settles. The thing that matters most is whether it is infected.
Knee bursitis symptoms depend on which bursa is involved, and where the swelling sits usually tells you which one it is and why. A swelling behind the knee is included because it is so often mistaken for bursitis.
| Over the kneecap prepatellar | Below the kneecap infrapatellar | Inside, below the joint pes anserine | Behind the knee Baker’s cyst | |
|---|---|---|---|---|
| What you notice | A soft, obvious swelling on the front | Swelling just below the kneecap | Tenderness more than swelling | Fullness or tightness at the back |
| Who tends to get it | People who kneel a lot — cleaners, tilers, gardeners | Kneeling more upright, as in prayer | Runners, and people with knee arthritis | People with arthritis or a cartilage tear |
| Usual cause | Pressure, or a knock or graze on the kneecap | Pressure from kneeling | Overuse, or wear inside the knee | A problem inside the joint pushing fluid backwards |
| What it needs | Protection, and a check for infection | Protection | Easing the load, treating any arthritis | Treating the problem inside the knee |
A swelling that is red, hot and very painful may be infected — especially if you had a graze or cut on the knee from kneeling, or you feel feverish. That needs seeing the same day, because an infected bursa is treated differently and can spread. Call the clinic and come in.
The bursa over the kneecap sits between the skin and the bone, just under the surface. Constant pressure or a knock irritates it, and it fills with fluid. The result can be a startlingly large, soft swelling on the front of the knee.
What a picture cannot show is that the fluid is outside the knee joint itself. That is why, with most bursitis, the knee still bends and straightens reasonably well despite how it looks — and it is one of the ways it is told apart from fluid inside the joint, which stiffens the whole knee.
It also explains why an infection matters so much here. The bursa lies right under the skin, so a small graze from kneeling is enough to let bacteria in.
A swelling behind the knee is worth looking into properly. A Baker’s cyst is usually a sign of something inside the joint, such as arthritis or a cartilage tear, and treating that is what settles it. Rarely, a swollen calf below it points to something else entirely, which is another reason not to guess.
Most knee bursitis settles without an operation. What decides the approach is whether it is infected, and whether it keeps coming back.
Stop kneeling on it, or use a well-padded knee pad where you cannot avoid it. Ice and rest help the swelling settle. For bursitis that is not infected, this is usually enough, over a few weeks.
A large, tense swelling can be drained with a needle, which eases it quickly and lets the fluid be tested. A steroid injection into the bursa is sometimes added to calm it — but only once infection has been ruled out, because it would make an infection worse.
An infected bursa needs treatment for the infection, and often draining. It is watched closely until it settles, because it can spread into the surrounding skin.
Knee bursitis surgery is kept for a bursa that keeps filling up again, or will not settle. The bursa itself is removed, sometimes through keyhole incisions. You can usually walk soon afterwards, though kneeling is best avoided while it heals.
Knee bursitis here is seen by Dr Kelvin Tan Guoping, an orthopaedic surgeon whose subspecialty is hip and knee. He is a Fellow of the Royal College of Surgeons of Edinburgh, holds a Master of Medicine in orthopaedics, and is an Adjunct Assistant Professor at NUS. He consults in English, Mandarin, Teochew and Hokkien.
No. Pushing a needle or anything else into the swelling risks letting infection in, which turns a nuisance into a real problem. If it needs draining, it should be done cleanly, and the fluid can be tested at the same time.
It is best to stop while it settles, since kneeling is usually what caused it. Where you cannot avoid it, a thick, well-padded knee pad takes most of the pressure off, and helps stop it coming back.
Not quite. Bursitis is fluid in a cushion outside the joint, so the knee usually still moves fairly well. Fluid inside the joint itself tends to stiffen the whole knee and usually points to a different problem.
It can, particularly if the kneeling continues. Protecting the knee is the best prevention. For a bursa that keeps filling up despite that, removing it is an option.
It is often called that, but it is usually fluid pushed out from the knee joint itself, because of arthritis or a cartilage tear. That is why the treatment focuses on what is happening inside the knee.
No. Let us know when you book if the swelling is red, hot or very painful, so you can be seen promptly.
Tell us when you book if the swelling is red, hot or very painful. That decides how soon you should be seen.
