A swollen knee is a sign, not a diagnosis. If the swelling comes within an hour of a twist or blow it is usually blood in the joint, which points to a cruciate ligament or meniscus injury and needs assessment. If it comes gradually over a day after loading it is joint fluid from irritation: overload, osteoarthritis or a meniscus injury irritating the joint. A soft swelling in front of the kneecap is a bursa, a lump in the back of the knee a Baker's cyst, and a hot, red knee with fever an infection or gout that needs urgent care. What helps with swelling without a serious cause is offloading, cold, elevation, gentle movement that pumps the fluid out, and lymphatic drainage with cups around the knee (not on it). Here are the causes, the warning signs, the self-care and how to cup.
What has swollen?
| Cause | Recognised by | What helps |
|---|---|---|
| Blood in the joint after injury | Tense swelling within an hour of a twist, jump or blow, often a pop, hard to bend and bear weight | Urgent assessment: cruciate ligament, meniscus, fracture, dislocated kneecap |
| Joint fluid from overload | Softer swelling that comes over a day after long sessions, stairs, squats or a new programme; feels "thick" and stiff | Offloading, cold, elevation, gentle movement, lymphatic drainage; gradual return |
| Osteoarthritis | Swelling that comes and goes, morning stiffness, clicking, ache after loading, usually over 50. See the guide to knee osteoarthritis | Exercise, weight control, self-care during flares |
| Meniscus injury | Swelling after a twist or deep squat, locking, pain on the inner or outer joint line | Assessment; most are rehabilitated without surgery |
| Bursa (bursitis) | Soft, well-defined lump in front of the kneecap after kneeling (housemaid's knee), the joint itself is not swollen | Offloading, knee pads, cold; medical care if red, hot or tender |
| Baker's cyst | Tense lump in the back of the knee, tightness when the knee is straightened; usually a consequence of osteoarthritis or a meniscus injury | Treat the cause; if the cyst bursts it gives sudden pain and swelling in the calf, assessed to rule out a clot |
| Inflammation or infection | Hot, red, very tender knee, fever, sometimes several joints; gout gives sudden severe pain | Urgent care |
| Swelling around the knee from fluid retention | The whole lower leg swollen, pits on pressure, often both sides; the joint itself moves freely. See the guide to fluid retention | Elevation, movement, lymphatic drainage; medical care if one-sided with pain (clot) |
Seek care if
Seek urgent care if the knee is hot, red and very tender with fever (infection), if the swelling came within an hour of an injury and you cannot bear weight or straighten the knee, if the knee locks and cannot be straightened, if you have sudden severe pain and swelling in the calf (clot or ruptured Baker's cyst), or if the kneecap has dislocated. Contact your doctor if the swelling has not decreased in one to two weeks with self-care, if the knee swells repeatedly without a clear cause, if you have swelling in several joints, if you have a lump in front of the knee or in the back of the knee that does not go away, or if the knee is unstable and gives way.
Baker's cyst: exercises and what helps
A Baker's cyst is a fluid-filled bulge in the back of the knee that arises when the knee produces more joint fluid than usual, almost always because of osteoarthritis or a meniscus injury. It feels like a tense lump in the back of the knee, feels tight when you straighten the knee or climb stairs, and varies in size with how irritated the knee is. The cyst itself is harmless and rarely needs draining or surgery; it shrinks when the cause in the knee settles. What helps is therefore the same as for a swollen knee: offloading in flares, cold, elevation and lymphatic drainage around the knee (never on the cyst), and above all exercises that reduce the irritation in the joint: thigh tensing with a straight leg (10 x 5 seconds, several times a day), straight leg raises 3 x 10, bridges 3 x 10, sit-to-stand squats 3 x 10 without going deeper than is pain-free, calf raises 3 x 15, cycling without resistance 10–20 minutes, and a light hamstring stretch 30 seconds (do not stretch hard into the back of the knee). Two to three times a week for at least eight weeks, together with the osteoarthritis training. Seek care if the cyst suddenly becomes very painful and the calf swells (a ruptured cyst, which must be distinguished from a clot), if the knee locks, or if the lump is hard, grows or exists without knee problems.
Self-care for a swollen knee without a serious cause
- Offload, but keep it moving. Avoid what caused the swelling for a few days to weeks (stairs, deep squats, running), but bend and straighten the knee in a pain-free range several times a day. Complete stillness keeps the fluid there and weakens the muscles quickly.
- Cold for 15 minutes, several times a day in the first days after an overload or minor injury. Not directly on the skin.
- Elevation: the leg above heart level for a while several times a day and at night, so the fluid drains back.
- Compression with an elastic bandage or knee sleeve during the day in the first days, not so tight that the foot goes numb.
- Pump exercises: tense the thigh muscle with a straight leg (10 x 5 seconds), ankle pumps, straight leg raises lying down, 3 x 10, several times a day. The thigh muscle is the knee's most important pump and swelling switches it off quickly.
- Gradual return: cycling without resistance, then walking, then stairs, then running, with a pain-free day at each level. Strength training for thighs and glutes as in the guide to runner's knee and sensitive knees.
- Over-the-counter anti-inflammatories for a few days can reduce swelling from irritation; ask the pharmacist if you have other conditions or medication. A doctor can drain fluid if the joint is very tense, but the fluid returns if the cause is not addressed.
Lymphatic drainage with cups around the knee
With swelling without injury or infection, light lymphatic drainage around the knee can help the fluid drain back towards the lymph nodes in the groin. The principle is to open the path upwards first (the thigh) and then work from the knee upwards, with very light suction. You cup around and above the knee and on the thigh, never over the kneecap itself, the joint line or a bursa. Use the dynamic cup with the lightest possible suction and massage oil.
- Lie on your back with the leg slightly raised on a pillow. First stroke with a flat hand from the knee up to the groin, ten times, and press lightly in the groin crease five times: that opens the lymph path.
- Thigh: long, light strokes from just above the knee up towards the groin, on the front and inside, two minutes. That is where the fluid should go.
- Around the knee: small, very light strokes from the sides of the knee (inside and outside of the joint, not the joint line) upwards towards the thigh, one minute per side. Skip the kneecap entirely.
- Calf: if the lower leg is swollen too, light strokes from the ankle up towards the back of the knee and on up the back of the thigh, two minutes.
- Finish by stroking with the hand from the knee to the groin again, and do ankle pumps. Daily during the swelling period, five to ten minutes. More on the technique in the guide to lymphatic drainage and swollen legs and feet.
Do not cup a hot, red knee or with fever, within three days of an injury or if there is blood in the joint, with a suspected clot in the calf, over the kneecap, joint line or a bursa, after an injection or aspiration (wait a week), or with reduced sensation. For osteoarthritis, the cupping program for sensitive knees applies, which works on the thigh and calf outside flares.
Frequently asked questions
Why is my knee swollen without an injury?
Usually joint fluid from overload (long sessions, stairs, a new programme) or an osteoarthritis flare, in older people and with repeated swelling. A soft lump in front of the kneecap is a bursa from kneeling. Swelling in several joints, or a hot and red knee, should be assessed.
How do you get rid of fluid on the knee?
Offload what caused the swelling, cold, elevation, compression, pump exercises for the thigh muscle and light lymphatic drainage around the knee. Over-the-counter anti-inflammatories for a few days can help. A doctor can drain fluid if the joint is very tense, but the fluid returns if the cause is not addressed.
Does cupping help a swollen knee?
As light lymphatic drainage around and above the knee with swelling without injury or infection, yes: it helps the fluid drain back towards the groin. Never cup over the kneecap or joint line, not within three days of an injury, and not a hot and red knee.
How long does a knee stay swollen?
Swelling from overload decreases in a few days to a week with offloading and self-care. Swelling after an injury can take weeks. If it does not decrease in one to two weeks, or comes back repeatedly, let a clinician assess it.
What is a Baker's cyst?
A fluid-filled bulge of the joint capsule in the back of the knee, which arises when the knee produces more joint fluid than usual, usually from osteoarthritis or a meniscus injury. Treatment is directed at the cause. If the cyst bursts you get sudden pain and swelling in the calf, which should be assessed to distinguish it from a clot.
Sources
- 1177 Vårdguiden (Swedish national health guide), search for "svullet knä", "Bakercysta" and "knäskador" for medical information and when to seek care.
- Curam's FAQ and cupping programs, developed with trained massage therapists.
Written by Curam. Last updated 17 October 2026. This is general self-care information and does not replace medical care. For sudden, severe or unusual symptoms, contact your doctor. Talk to your doctor before cupping if you are pregnant, take blood thinners or have a condition affecting skin, blood vessels or blood.
