Bursae of the Knee: Where They Sit and What They Do

The bursae of the knee are small sacs of fluid that sit between bone and the tissues that slide over it. Each one works like a tiny water cushion, so skin, tendons and muscles can glide instead of rubbing. Several sit around the knee, and a handful of them come up most often when a knee starts to ache. I teach the Feldenkrais Method®, so alongside the anatomy I will keep asking how these places feel from the inside.

What a bursa is, in plain words

A bursa is a thin, flattened bag. Its lining makes a little slippery fluid. When all is calm, it holds only a film of that fluid, a few drops. You cannot see it, and you cannot feel it as a lump. It simply lets two surfaces pass each other with very little friction, over and over through the day.

Think of the front of your knee as you kneel. Or think of the tendons on the inner side of your shin as you climb a step. Each of those places takes pressure or rubbing. A bursa sits there so the load spreads out and the movement stays smooth. Bones, cartilage and ligaments get most of the attention in diagrams, and the knee anatomy explainer walks through all of them. The bursae are the quiet helpers in between.

Where the main bursae of the knee sit

Prepatellar bursa. This one lies in front of the kneecap, right under the skin. It is the bursa you lean on when you kneel to garden, scrub a floor or lay tiles. Because it sits so close to the surface, a swelling here shows as a soft bump over the kneecap. People sometimes call it patella bursitis. Our guide to prepatellar bursitis looks at that swelling in more depth.

Infrapatellar bursae. Just below the kneecap runs the thick patellar tendon, which joins the kneecap to the shin. Two small bursae live here. One sits under the skin, in front of the tendon. The other sits deeper, between the tendon and the top of the shin bone. Kneeling upright, with your weight on the shins, tends to press on the one in front.

Pes anserine bursa. Pes anserine means goose foot. A few fingers below the joint line, on the inside of the shin, three tendons from the thigh fan out and attach to the bone. Their shape looks a little like a webbed foot. The bursa lies underneath them. Our guide to pes anserine bursitis covers the tender spot that can form there. People often notice it on stairs or when rising from a chair.

Suprapatellar bursa. Above the kneecap, between the front thigh tendon and the thigh bone, sits a larger pouch. In most people it opens straight into the knee joint. It gives that tendon room to slide up and down as the knee bends. When the joint swells from the inside, this pouch can fill too, so the area above the kneecap looks puffy.

The back of the knee has smaller bursae as well. One sits near the semimembranosus, a hamstring tendon on the inner side. These are harder to feel and come up less often, so I will leave them there.

What the bursae of the knee do all day

Every time you bend or straighten your knee, something slides. The kneecap glides in its groove on the thigh bone. The patellar tendon moves over the top of the shin. The goose foot tendons sweep across the inner shin. Without bursae, those surfaces would rub on bone and on each other. With them, the movement stays quiet.

The bursae also spread pressure. When you kneel, the prepatellar bursa sits between your weight and the hard kneecap, so the skin is not pinched against bone. They are padding as much as lubrication. They do not hold the knee together, and they do not move it. Ligaments and muscles do that. The bursae just make the moving easier.

How an irritated knee bursa feels

Bursitis means an irritated or inflamed bursa. The lining reacts and makes far more fluid than usual, so the sac swells. Common symptoms of bursitis in the knee include:

• a soft swelling over one spot, sometimes a little squishy,
• tenderness when you press that spot,
• warmth over the area,
• pain when you kneel, or when you go up or down stairs,
• an ache that grows after a busy day and eases with rest.

When the bursa sits outside the joint, like the one in front of the kneecap, the knee often still bends fairly well. The swelling rests on top instead of inside. That is one clue that sets it apart from a swollen joint, though only an examination can say for sure.

The usual triggers are simple. Lots of kneeling is the classic one. That is why old names, such as housemaid's knee, point to jobs done on all fours. A knock or a fall onto the knee can start it. Repeated friction, from cycling, running or a long day of stairs, can irritate the pes anserine bursa. Sometimes a cut or graze over the kneecap lets germs in, and that needs a doctor.

Bursitis can turn up in any joint, the NHS explains, yet shoulders, hips, elbows and knees are where it appears most, and it normally clears up within a few weeks; if a week or two of home care brings no change, it advises seeing a GP (NHS, 2023). The Feldypedia entry on bursitis gives a wider view across the body.

Moving gently around a sore bursa

While a bursa settles, the kindest thing is often to stop pressing on it. Kneel on a thick cushion for a while, or not at all. Notice how often you lean on the front of the knee without meaning to: climbing into the bath, reaching under a bed, picking up something a child dropped.

Resting the bursa is not the same as freezing the whole leg. The hip, the ankle and the foot still like to move. Slow, small, easy movement around them keeps the leg feeling alive. It also gives the knee a clearer sense of where it is. That inner sense of position is called proprioception.

Try this while sitting. Slide one foot forward a little along the floor, then back. Keep it smaller than you think it needs to be. Notice whether the kneecap glides, and whether the front of the thigh grips. Then do the same with the other leg and compare. If the sore spot complains, make the movement smaller still, or stop.

For more slow sensing like this, the knee proprioception exercises page is a good next step. There is also a set of knee bursitis exercises built from small, comfortable movements. Feldy offers short audio lessons in the Awareness Through Movement® style. You can begin with a free 7 day trial, and the knee and hip page shows how the lessons are shaped for tender knees.

Alongside clinical care and other methods

If a GP or a physiotherapist is looking after your knee, gentle awareness work sits beside their plan. It never takes its place. They may suggest rest, cold packs, a new way of kneeling or strength work. Follow their guidance on what suits your knee.

Other movement methods offer their own ways in. Strength training builds capacity in the muscles around the knee. Yoga works through held shapes and steady breathing. Pilates builds control through precise, repeated movements. Tai chi uses slow weight shifts from one foot to the other. Feldenkrais works through very small movements and attention to how the whole leg shares the work. Each rests on a different mechanism, and many people mix more than one.

When a swollen knee bursa needs a doctor

Most irritated bursae settle with time and less pressure. A few need prompt attention. If the knee is hot, red and very swollen, especially with a fever or a general sense of being unwell, the bursa may be infected. That needs medical care quickly, not home practice. See a GP too if there is no change after 1 to 2 weeks, if the swelling keeps growing, if you cannot bend the knee, or if the pain began with a hard fall.

Common Questions about the bursae of the knee (FAQ)

Is it safe to move my knee when a bursa is swollen?

Usually, yes, as long as you keep the movement small, slow and well inside what feels easy. Take pressure off the swollen spot and let the hip, ankle and foot do gentle work around it. If the knee is hot, red and very swollen, or you feel feverish, skip home practice and get it checked.

How long does an irritated knee bursa take to settle?

Many settle within a few weeks once the kneeling or rubbing that set them off eases. Some calm down sooner, and a bursa that has flared more than once may take longer. If you see no change at all after a week or two of looking after it, book a visit to your GP.

How can I tell bursitis from swelling inside the knee joint?

A bursa in front of the kneecap swells on the surface, like a soft bump sitting on top, and the knee often still bends fairly well. Swelling inside the joint tends to make the whole knee feel full and tight, often with puffiness above the kneecap and a stiff bend. These are only clues. A clinician can tell you which one you have.

What should I avoid with an irritated knee bursa?

For a while, avoid kneeling on hard floors, leaning on the front of the knee, and long sessions of the activity that started it. Avoid pressing or rubbing the swollen spot to test it. Let any ache over the bursa decide how much you do, and stop if a movement makes the swelling feel worse.

How often should I do gentle movement while a knee bursa settles?

A few minutes once or twice a day is plenty. Short, easy sessions keep the leg moving without loading the sore place. Sitting or lying positions work well, because they take your weight off the knee. Pay attention to how the knee feels later that day and the next morning, and adjust from there.

What is the best way to kneel if the bursae of the knee are sensitive?

Kneel on a thick, soft cushion or a gardening pad, and change position often. Spread the weight across the shins instead of resting on the kneecaps, or sit on a low stool instead. Notice how long you have been kneeling, and get up before the front of the knee starts to complain.

When should I see a doctor about a swollen knee bursa?

Get prompt medical care if the knee is hot, red and very swollen, especially with a fever or a general sense of being unwell, since that can mean infection. See a GP if there is no improvement after 1 to 2 weeks, if the swelling keeps growing, if you cannot bend the knee, or if pain started with a hard fall.