Joint swelling

Where two bones meet, the joint is wrapped in a capsule, and the capsule's lining makes a small amount of fluid that lets the surfaces glide. A swollen joint is bigger than it should be for one of four reasons, and they feel different under the hand:

• Extra fluid inside the joint. An injured or inflamed joint fills with more fluid than it needs. Doctors call this an effusion; at the knee it is the "water on the knee" of everyday speech. The swelling is soft, and the joint feels stiff and heavy and will not bend as far as usual.
• An inflamed lining. With an inflammatory arthritis it is the joint's lining that is inflamed, which is called synovitis. The joint is puffy and soft to press, not bony, and it is warm, tender and stiff after rest.
• Bone. In osteoarthritis small spurs of extra bone grow at the ends of the bones within the joint, and the joint ends up slightly larger and knobbly: a hard swelling, which stays.
• Something beside the joint. A bursa that has filled, a cyst, or fluid in the tissues of the limb can each pass for a swollen joint. They have a section to themselves below.

The four can overlap. A knee with osteoarthritis can have the hard outline of its bony spurs and, when it is inflamed, a soft swelling of extra fluid as well.

The causes, and what marks each one out:

• An injury. A sprain or a strain leaves the area swollen or bruised, and most feel better after two weeks. How quickly the swelling arrives is worth noticing. A knee that becomes very swollen and tense within about two hours of a twist, a fall or a blow, or that gave a pop or a snap, suggests a torn ligament, a break or a dislocated kneecap, and is a 999 or A&E emergency, as is a shoulder that is painful, bruised or swollen after it slipped out of place; a kneecap that slipped out of place and went back on its own needs NHS 111 that day, and another joint that swells this fast after an injury needs assessing that day, through NHS 111 or at an urgent treatment centre. Swelling that builds over the next day or two fits a sprain or a torn cartilage, and can be cared for at home unless it is large or goes on growing, in which case call NHS 111 the same day. After an injury, a joint that takes no weight, cannot be moved or is still out of place, very bad pain, any tingling or loss of feeling, a crack heard as it happened, or skin around it turned blue, grey or cold, is a 999 or A&E emergency; the first list under "When to seek help" has them all.
• Wear. Osteoarthritis enlarges a joint with bone and, when the joint is inflamed, adds fluid to it. Mild swelling of both knees in later life, with pain on walking and stiffness on waking that is gone inside half an hour, is its pattern at the knee, which our knee pain guide takes further; at the fingers it shows as bumps on the joints.
• A crystal attack. Gout strikes suddenly, often overnight: the joint, usually the big toe, turns hot, swollen and red and is very painful, though it can be another joint of the foot, the ankle, the knee, the hand, the wrist or the elbow. Pseudogout involves a different crystal, is rare before 60, and affects the knee most often, and sometimes the wrist, the shoulder or the ankle. Both respond to treatment, but infection in a joint produces the same picture, which is why a joint that suddenly becomes hot and swollen sits among the same-day signs below; a typical attack of gout or pseudogout that has already been diagnosed is dealt with in its own guide.
• Inflammation of the joint lining. One joint or several that are soft, warm and tender, stiff for a good half hour or more after getting up, and still swollen after a week or two: this is the pattern of an inflammatory arthritis. Rheumatoid arthritis often shows first in the smaller joints of both hands and both feet; psoriatic arthritis can swell a whole finger or toe; reactive arthritis follows an infection by one to four weeks and favours the knees and the feet, and a viral illness can leave swollen joints behind it too, which our viral arthritis guide covers. Swelling that comes in attacks of hours or days, with the joints back to normal in between, is the pattern of palindromic rheumatism. Until the cause has a name the picture is called early inflammatory arthritis, and its guide explains why a GP should see it within days and not wait and watch.
• Bleeding into the joint. A knee or another joint that swells and feels warm, sometimes with bruising, in someone who takes a blood-thinning medicine may have blood in it, and with a bleeding disorder such as haemophilia a joint that becomes painful or swollen may have the same. On a blood-thinning medicine, call NHS 111 or go to A&E the same day; with a bleeding disorder the haemophilia team, if you are under one, is the first call, and NHS 111 if it cannot be reached.
• An infection. Direct infection of a joint, septic arthritis, is rare, and it is a cause that cannot be left. It usually affects one joint, which becomes very painful, hot and swollen in a matter of days, sometimes without a fever. It is likelier in a joint that has been replaced or recently operated on, and in people with diabetes, rheumatoid arthritis or a weakened immune system; the septic arthritis guide has a section on who is at higher risk. Because an infected joint and a crystal attack can look the same, every joint that becomes hot and swollen without warning is seen the day it happens, by the routes in the same-day list under "When to seek help", a typical attack of gout or pseudogout already diagnosed being the exception its own guide sets out.
• Two further causes. A single joint, the knee in most cases, that swells and stiffens gradually in an adult between about 20 and 50 is occasionally a tenosynovial giant cell tumour: an overgrowth of the joint lining that is not a cancer and does not spread, though it can damage the joint if it is left; it is seen best on an MRI scan and usually removed by a surgeon. And where diabetes has dulled the feeling in the feet, a foot or ankle that becomes swollen or warm, or changes colour or shape, sometimes with little pain or none, can be a Charcot foot, in which the bones and joints are giving way; it needs seeing that day, through a GP, the diabetes foot care team or NHS 111, with all weight kept off the foot until then.

Some swelling hardly hurts at all. That is neither a reassurance nor an alarm in itself; it depends on which kind of swelling it is:

• Bony enlargement. The bumps of osteoarthritis on the finger joints can remain after the pain has faded.
• A cyst. A Baker's cyst behind the knee, or a ganglion at the wrist or on the top of the foot, may be a lump and nothing more.
• Fluid in the tissues. Puffy ankles and feet after long standing or sitting are fluid in the tissues of the leg, not in the joints.
• Rarely, an overgrowth of the joint lining. A painless swelling of one joint is sometimes the first sign of the tenosynovial giant cell tumour described above.
• A foot or ankle, in diabetes. Swelling or warmth there with little pain is a warning in its own right and is seen the same day, as the section above says.

Whatever the pain is doing, the signs in the two lists under "When to seek help" still apply, a single ankle, foot or leg swollen for no clear reason and the foot in diabetes among them. Two rules are worth stating for swelling that does not hurt. A joint that is soft and swollen, and has been for more than a week or two without an injury to account for it, is for a GP within days: what counts is the swelling and how long it has lasted, not the pain. And a lump you cannot account for is shown to a GP, promptly if it is growing or is hard and fixed.

Swelling at a joint is not always swelling of the joint. What can be mistaken for it:

• A bursa. Bursae are the small fluid-filled sacs that cushion the joints. An inflamed one fills and swells, and is achy, tender or warm, and sorer when pressed or moved; it shows as a soft bulge at the back of the elbow, or over the kneecap after a lot of kneeling, and the shoulder and the hip are its other usual sites. It can usually be treated at home and should settle within a few weeks, with a routine visit to a GP if a week or two of that has not eased it; our bursitis guide covers it. A bursa can also become infected, so one that turns hot, red or very painful, or that comes with a fever, is seen the same day; feeling hot, cold or shivery with it, or another of the signs the list under "When to seek help" gives for hot skin beside a joint, makes it a 999 or A&E emergency, and that list gives the routes.
• A Baker's cyst. A soft lump of fluid behind the knee, which in adults usually goes with another problem in the knee, such as osteoarthritis; our Baker's cyst guide explains.
• A ganglion. A soft, smooth lump beneath the skin, close to a joint, usually at the wrist or the hand and now and then on the top of the foot, and usually painless. It has a guide too, ganglion cysts. A lump that turns very painful, hot or red is one of the same-day signs, or a 999 or A&E emergency with the signs that list gives.
• Fluid in the tissues. Ankles, feet or lower legs that are puffy, with shiny, stretched skin that keeps a dent when pressed, are holding fluid in the tissues, which is called oedema. Long spells of standing or sitting, extra weight, pregnancy and some medicines are the usual reasons, and the heart, the kidneys or the liver the less usual ones. If both legs are swollen, see a GP if a few days of care at home have not helped, if the swelling is getting worse, or if you have a heart, kidney or leg-vein condition. A GP or NHS 111 the same day is right if the swelling is severe or painful, came on very suddenly or takes in the face or tummy as well, and for swollen feet, ankles or legs if you have diabetes; and if you are pregnant and your face, hands or feet swell suddenly, call your midwife or maternity unit at once. Swelling of one leg only is a different matter, described next.
• A clot in a leg vein. One ankle, foot, calf or leg that swells for no clear reason, with or without a throbbing pain or skin gone red or darker, can be a deep vein thrombosis. It has to be seen the day it appears, through an urgent GP appointment or NHS 111, and if breathlessness, chest pain, a racing heart or faintness comes on while a leg is swollen, that is a 999 or A&E emergency. A Baker's cyst that has burst can look the same, so a swollen calf is examined, never assumed to be the cyst.
• An infection of the skin. Skin over or near a joint that is painful, hot and swollen can be cellulitis, an infection in the skin and not in the joint. It is seen that day through an urgent GP appointment or NHS 111, or, with a fever or feeling ill, short of the signs that follow, at A&E or through NHS 111; with a very high temperature or feeling hot, cold or shivery, a fast heartbeat or fast breathing, purple patches on the skin, which may be less obvious on black or brown skin, feeling dizzy or faint, confusion, or skin that is cold, clammy or pale, it is a 999 or A&E emergency, as it is with the signs of sepsis in the first list under When to seek help.

Speed comes first: whether the swelling came within hours, over a few days, or crept up over weeks. The rest of the account follows: one joint or several, an injury or none, how long the joint stays stiff after waking, whether this has happened before, and what else has been going on, a recent infection or fever, a skin rash, psoriasis, trouble with the bowel, the medicines you take. On examination the swollen joint is compared with the one on the other side: for warmth, for the kind of swelling, bony, fluid or a bursa, for tenderness and for how far it moves.

Point-of-care ultrasound is part of the consultation with Dr Borukhson, and it is well suited to a swollen joint. In the same visit the scan shows whether the joint holds extra fluid, whether its lining is inflamed, whether the swelling is a bursa or a Baker's cyst and not the joint, and whether a tendon beside the joint is the part at fault. It can show inflammation too slight to feel, though a scan that finds none does not rule an inflammatory arthritis out where the story points to one, and it guides the needle when a sample is wanted. Our ultrasound clinic page says more about the scan.

Where the cause is still open, or the joint is hot, a sample of the fluid usually settles it. A fine needle draws some off, which also eases a tense joint, and the laboratory looks in it for crystals, urate in gout and calcium in pseudogout, and tests it for infection. The joint aspiration guide goes through the procedure.

The blood tests are chosen by what the picture suggests: the markers of inflammation, urate where gout is suspected and, where the lining is inflamed, the antibodies of rheumatoid arthritis, rheumatoid factor and anti-CCP. An X-ray shows bony change and, after an injury, a break; an MRI scan looks at the ligaments and cartilage inside a joint and at the rarer conditions of its lining. By the end of the visit the kind of swelling is usually clear and its cause often is; where a sample has gone to the laboratory, its result completes the picture.

The cause decides the treatment:

• An injury is protected, rested, iced, supported and raised for the first two or three days and then moved again as the pain lets it; where a ligament or a cartilage is torn, physiotherapy or a surgeon's opinion may follow.
• Osteoarthritis is managed as a whole, with exercise, weight loss where it is needed and pain relief, and a steroid injection can reduce the swelling and pain of a knee that has flared; the osteoarthritis guide gives the detail.
• A crystal attack is calmed with an anti-inflammatory medicine, with colchicine, or with a steroid, which is taken as tablets or injected into the joint once the fluid has been drawn off; preventing the next attack of gout is a separate, longer treatment, which its guide describes.
• An inflammatory arthritis is treated early with medicines that change the way the immune system is behaving, the route the early inflammatory arthritis guide follows.
• An infected joint is usually treated in hospital, with antibiotics into a vein and, often, the joint drained.
• Bursitis usually settles with rest, ice and painkillers; fluid can be drawn off, a steroid injection given where there is no infection, and antibiotics where there is.
• A Baker's cyst tends to improve when the knee problem behind it is treated, and a ganglion can often be left alone.
• Fluid in the tissues is treated by its cause, and a clot with blood-thinning medicine.

Drawing off fluid and injecting a joint are both done under ultrasound guidance, usually in the visit at which the need becomes clear; the ultrasound-guided injections guide explains. You and Dr Borukhson settle the plan together.

Until a swollen joint has gone down, or has been seen:

• Rest the joint without immobilising it: gentle movement keeps it from stiffening
• Cool a newly swollen joint: ice, or frozen peas, in a towel, kept on for up to twenty minutes, with a gap of two to three hours before the next; after an injury, heat, alcohol and massage are best avoided for the first couple of days
• Raise the limb when you sit or lie, and after an injury support the joint with a bandage through the day
• Ask a pharmacist about pain relief: paracetamol, or ibuprofen, which comes as a gel and as tablets, where it is safe for you. Ibuprofen gel makes any clothing it gets on burn more easily, so while you are using it, do not smoke, and stay well clear of naked flames
• Take the weight off a swollen foot or ankle if you have diabetes, straight away, and keep it off until you have been seen, which should be that day, through a GP, the diabetes foot care team or NHS 111
• Note when the swelling began, how fast it came and what went before it, and photograph the joint at its most swollen, since it may have gone down again before the appointment
• Do not squeeze or prick a lump: bursting a ganglion at home can infect it or harm the skin
• If you are overweight, losing some weight helps in the longer run, since extra weight puts more pressure on the joints

Swelling from a knock or a minor sprain that is already going down can be cared for at home. The signs in the two lists that follow should not wait.

Treat any of these as a 999 or A&E emergency: call 999 and do not drive yourself to A&E.

• Severe illness with suspected sepsis: a high fever with shaking, confusion, rapid breathing, or feeling dramatically worse over hours
• With a fever or feeling unwell, a rash that does not fade when you press it, a stiff neck with eyes that cannot bear bright light, or skin, lips or tongue turning blue, grey, pale or blotchy, since these can be signs of meningitis or sepsis, as can a very bad headache, confusion or a first seizure with a fever or feeling unwell; on black or brown skin the rash and the change of colour may be easier to see on the palms of the hands or the soles of the feet
• A joint you cannot put weight on or move, or that has moved out of place, or, after a fall or injury, very bad pain or any tingling or numbness
• After an injury, a crack heard as it happened, or skin around it that has turned blue, grey or cold, since these can be signs of a broken bone
• Breathlessness that is severe, with gasping, choking or no breath to get words out; coughing up blood; or chest pain that catches as you breathe in, since a clot in the leg can travel to the lungs; with a swollen or painful leg, any breathlessness or chest pain belongs here, and so do a racing heart and feeling faint
• Chest pain that is crushing, tight or like a pressure, that spreads to an arm, the jaw, the neck, the stomach or the back, that comes with breathlessness, sweating, feeling sick or feeling light-headed, or that came on suddenly and does not go away
• Palpitations happening now that do not stop, or that come with chest pain, breathlessness, feeling faint or fainting, since a heart whose muscle or rhythm is affected has to be checked at once
• Lips, mouth, throat or tongue that suddenly swell, a throat that feels tight, very fast breathing or a struggle to breathe or to swallow, skin, tongue or lips turning blue, grey or pale (on black or brown skin this may be easier to see on the palms of the hands or the soles of the feet), becoming suddenly very confused, drowsy or dizzy, or fainting and not being able to be woken, since this can be a severe allergic reaction, anaphylaxis, which can follow a dose of any medicine
• An eye that suddenly and completely loses its sight

Any of these needs an assessment that is urgent, on the same day, from your GP or NHS 111:

• A joint that is hot and swollen, with a fever or feeling unwell, since an infected joint has to be ruled out at once, at A&E or through NHS 111
• A joint that has become hot and very swollen suddenly, or is worsening quickly, even without a fever, since an infected joint does not always announce itself with one
• Joint pain with a fever, or feeling hot, cold or shivery, or generally unwell, since an infection in or around a joint has to be found the same day
• A knee that is badly swollen, whether or not it is hot, since swelling of that size should have its cause found without waiting; NHS 111 can say where to be seen
• A bursa, a lump or a patch of skin beside a joint that has turned hot, red or very painful, since infection beside a joint can turn serious if it is not treated quickly; with a fever or feeling ill, short of the signs that follow, at A&E or through NHS 111; with a very high temperature or feeling hot, cold or shivery, a fast heartbeat or fast breathing, purple patches on the skin, which may be less obvious on black or brown skin, feeling dizzy or faint, confusion, or skin that is cold, clammy or pale, it is a 999 or A&E emergency: call 999 and do not drive yourself to A&E
• After an injury, a joint other than the knee that swells up large and tight within a couple of hours, a large amount of swelling or bruising, or swelling or bruising that is still getting worse, since a break or a torn ligament has to be ruled out; NHS 111 can say where to go, and an urgent treatment centre can sometimes X-ray it; a joint or limb left at an odd angle or out of shape after the injury, a knee that swells up very quickly or gave a pop or a snap, or a shoulder that is painful, bruised or swollen after it slipped out of place, is a 999 or A&E emergency
• A calf that is swollen, hot or painful, or a limb that is painful, swollen or discoloured, which can mean a clot; one ankle, foot or leg that has swollen for no clear reason counts as well; with breathlessness, chest pain, palpitations or feeling faint, this is a 999 or A&E emergency: call 999 and do not drive yourself to A&E
• New chest pain, new palpitations, or breathlessness that is new or getting worse; palpitations happening now that do not stop, or that come with chest pain, breathlessness, feeling faint or fainting, belong to the first list; in pregnancy, breathlessness that comes on suddenly, or when you lie down, or with dizziness, is for your midwife or maternity unit straight away
• Leg swelling that is severe or painful, that came on very suddenly, or that comes with a swollen face or tummy, since fluid that builds this fast or this widely needs its cause found the same day; in pregnancy, a sudden increase in swelling of the face, hands or feet is for your midwife or maternity unit straight away
• A foot or ankle that has become swollen or warm, or has changed colour or shape, if you have diabetes, since the bones and joints of a foot that has lost feeling can give way; take all weight off it at once, and ring the diabetes foot care team if you are under one; a swollen leg in diabetes needs the same day too
• A joint that swells and feels warm while you take a blood-thinning medicine, or a joint that becomes painful or swollen if you have a bleeding disorder, since there may be bleeding inside the joint; on a blood-thinning medicine go through NHS 111 or to A&E, and if you are under a haemophilia team, ring it first
• A new red, painful eye, or sight that has blurred, dimmed or changed, which needs an eye casualty or urgent eye clinic the same day, as does an eye that light hurts, since the same condition can inflame a joint and the eye, which psoriatic and reactive arthritis both do; our uveitis guide covers it; in pregnancy, any change in sight, blurring or flashing lights among them, is also for your midwife or maternity unit straight away, since it can be a sign of pre-eclampsia

Where none of the signs in the two lists applies, a GP should see you within days about a joint that is soft and swollen, sore or not, and still so after a week or two with no injury to explain it. The same pace holds for soft swelling in the small joints of a hand or a foot, or in several joints at once; for a whole finger or toe that has swollen; for swelling that comes with over half an hour of stiffness in the mornings; and for a joint whose swelling is getting worse or keeps coming back. These are the ways an inflammatory arthritis shows itself, and the early inflammatory arthritis guide says why the weeks count. Otherwise, a routine GP appointment is right for swelling of a joint that you cannot explain and that has not gone within a few days, for an injury that is no better after a fortnight of care at home, for a bursa that a week or two of the same care has not eased, and for puffiness of both ankles or lower legs, the kind that keeps a dent when pressed, that a few days of raising them have not eased. A lump you cannot account for should be shown to a GP too, promptly if it is growing or is hard and fixed, since a growing lump may need an urgent scan; swelling that comes with pain at night or at rest, with unexplained loss of weight, or after a cancer in the past should be shown to a GP promptly as well. A specialist assessment needs no referral, and in this practice next-working-day appointments can almost always be arranged, and same-day appointments are sometimes possible. If you cannot tell how urgent something is, asking is never a mistake.

Two things need finding out about a swollen joint: what kind of swelling it is and what has caused it. One visit can usually do both: examining and scanning the joint separates fluid, an inflamed lining, bony change and the things that sit beside the joint, and a sample of the fluid, where one is taken, can tell crystals from infection. That matters most for the joint that has been quietly swollen for weeks, where an inflamed lining is better found early than late, as the early inflammatory arthritis guide explains. A swelling that lingers or keeps returning is worth having its kind and its cause found.

What can make a joint swell?

Four things, broadly. Extra fluid can collect inside the joint, which is what 'water on the knee' means; the lining of the joint can become inflamed, leaving the joint soft, warm and tender; small spurs of extra bone can grow within the joint, as they do in osteoarthritis, giving a hard, knobbly outline; or the swelling can sit beside the joint and not in it, in a bursa, a cyst or the tissues of the limb. The main causes are an injury, wear, a crystal attack such as gout, an inflammatory arthritis and, rarely, an infection. The speed of the swelling, its feel and the number of joints involved go a long way towards telling them apart, and a joint that suddenly turns hot as well as swollen has to be seen the same day, by the routes the When to seek help section gives.

Does a swollen joint that does not hurt need attention?

It can, though not every swelling that hurts little does: the bumps of osteoarthritis on the finger joints can stay after the pain has gone, a ganglion at the wrist often goes away by itself, and ankles that puff up after long standing or sitting often go down again by themselves. But the absence of pain does not settle the matter. A joint that is soft and swollen without an injury behind it, and still so after a week or two, should be seen by a GP within days whether it hurts or not, because what sends an inflamed joint lining to a specialist is the swelling and how long it has lasted, not how much it hurts. An unexplained lump is one to show a GP, sooner if it is growing or is hard and fixed. A single ankle, foot or leg that has swollen for no clear reason needs a GP or NHS 111 the same day, even when it does not hurt. And if you have diabetes, a foot or ankle that has become swollen or warm, with little pain or none, needs help that day, from a GP, the diabetes foot care team or NHS 111, with the weight taken off it straight away.

Is it the joint itself that is swollen, or something next to it?

The place and the shape often tell. Swelling inside a joint makes the joint look larger than its partner on the other side, and leaves it stiff and harder to move. A swollen bursa is a soft swelling over the point of the elbow or the front of the kneecap, or tenderness at the side of the hip or the point of the shoulder; a Baker's cyst is a soft lump behind the knee; a ganglion is a smooth lump near the wrist or hand, or on the top of the foot. Puffiness that takes in the ankle, the foot or the lower leg, and keeps a dent when pressed, is fluid in the tissues. Some of this has to be seen the same day, through an urgent GP appointment or NHS 111: swollen feet, ankles or legs if you have diabetes; leg swelling that is severe or very sudden, or that arrives with puffiness of the face or tummy; and a bursa, a lump or a patch of skin that has turned hot, red or very painful, which a fever or feeling ill, short of the signs that follow, makes a matter for A&E or NHS 111, and which a very high temperature or feeling hot, cold or shivery, a fast heartbeat or fast breathing, purple patches on the skin, which may be less obvious on black or brown skin, feeling dizzy or faint, confusion, or skin that is cold, clammy or pale makes a 999 or A&E emergency, as do the signs of sepsis in the first list under When to seek help. A single ankle, foot, calf or leg that has swollen for no clear reason goes by the same route, a GP or NHS 111 that day, all the more with a throbbing pain or skin gone red or darker, since it can be a blood clot. Breathlessness, chest pain, a racing heart or feeling faint, when a leg is swollen, is a 999 or A&E emergency.

What is water on the knee?

It is the everyday name for extra fluid inside the knee joint, which doctors call an effusion. A healthy joint holds only a little fluid; a knee that has been injured or is inflamed holds more, so it looks puffy, feels stiff and heavy and bends less far. The fluid is a sign and not a diagnosis. Mild swelling of both knees in later life points to osteoarthritis, and swelling after a twist or a fall to a sprain or to a torn ligament or cartilage; a knee that turns hot and red, with sudden, very bad pain, points to gout, pseudogout or, rarely, an infection, and a knee that stays swollen for weeks, stiff for more than half an hour each morning, to an inflammatory arthritis. How soon it needs seeing differs as much as the cause does. A knee that will not take your weight, cannot be moved or has moved out of place is a 999 or A&E emergency, and so, after an injury, is a knee that swells up very quickly or gave a pop or a snap. A knee that is badly swollen is for NHS 111 that day. A hot, red knee is seen the same day, either at A&E or by calling NHS 111, if you have a fever or feel ill, and with shaking, confusion, rapid breathing, or feeling dramatically worse over hours is a 999 or A&E emergency, as the first list under When to seek help says, and without a fever or feeling ill through an urgent GP appointment, NHS 111 or a specialist clinic that can see you that day; a typical attack of gout or pseudogout already diagnosed is dealt with in its own guide. A knee that was not injured and has stayed soft and swollen past a week or two needs a GP within days. The treatment differs with each cause too, which is why the reason for the fluid has to be found.

How is the cause found, and will the fluid need to be drained?

From your account, an examination and a scan, with a sample of the fluid where it adds something. Point-of-care ultrasound is part of the consultation with Dr Borukhson, so a swollen joint is scanned there and then, and the scan tells fluid in the joint from an inflamed lining, and both from a bursa or a cyst lying beside it. The fluid is not always drained: it is drawn off through a fine needle when a sample will settle the question, since the laboratory can find urate or calcium crystals in it and test it for infection, or when a tense joint would be more comfortable with less in it, and ultrasound guides the needle to the fluid. Blood tests and an X-ray follow where the picture warrants them. Our joint aspiration guide describes what having fluid taken involves.

How quickly does a swollen joint need to be seen?

That depends on how fast it came and on what accompanies it. A joint that cannot be moved, will not bear weight or has moved out of place is a 999 or A&E emergency, injured or not; so, after an injury, are very bad pain, any tingling or numbness, a crack heard, skin turned blue, grey or cold, a joint or limb left at an odd angle or out of shape, a knee that swells up very quickly or gave a pop or a snap, or a shoulder that is painful, bruised or swollen after it slipped out of place; so are coughing up blood, a struggle for breath severe enough to have you gasping or choking, or unable to get a sentence out, chest pain that catches as you breathe in, and chest pain that is crushing, tight or like a pressure, that spreads to an arm, the jaw, the neck, the stomach or the back, that comes with breathlessness, sweating, feeling sick or feeling light-headed, or that came on suddenly and does not go away; so are breathlessness, chest pain, palpitations or feeling faint with a swollen leg; so are palpitations still going on that will not settle, or that bring chest pain, breathlessness, faintness or a faint with them; so are a high fever with shaking, confusion, rapid breathing, or feeling dramatically worse over hours, and, with a fever or feeling unwell, a rash that does not fade when you press it, a stiff neck with eyes that cannot bear bright light, or skin, lips or tongue turning blue, grey, pale or blotchy (on black or brown skin the rash and the change of colour may be easier to see on the palms of the hands or the soles of the feet), and a very bad headache, confusion or a first seizure with a fever or feeling unwell; so is a bursa, a lump or skin beside a joint gone hot, red or very painful, with a very high temperature or feeling hot, cold or shivery, a fast heartbeat or fast breathing, purple patches on the skin, which may be less obvious on black or brown skin, feeling dizzy or faint, confusion, or skin that is cold, clammy or pale; so is sight lost all at once; and so are the signs of a severe allergic reaction to a medicine, which the first list under When to seek help sets out. Call 999 and do not drive yourself to A&E. A joint that has gone hot and swollen over hours or a few days cannot wait past today: with a fever or feeling ill, get help the same day, either at A&E or by calling NHS 111; if you are well in yourself, use an urgent GP appointment, NHS 111 or a specialist clinic that can see you that day; a typical attack of gout or pseudogout already diagnosed is dealt with in its own guide. The same day, through a GP or NHS 111, is also the pace for new chest pain, new palpitations, or breathlessness that is new or getting worse (in pregnancy, breathlessness that comes on suddenly, or when you lie down, or with dizziness, is for your midwife or maternity unit straight away), for joint pain with a fever or shivering, and for a bursa, a lump or skin beside a joint that has turned hot, red or very painful, which goes to A&E or NHS 111 with a fever or feeling ill, short of the emergency signs above. The same holds for one ankle, foot, calf or leg that swells for no clear reason, for leg swelling that is severe or very sudden or comes with swelling of the face or tummy, and for a swollen foot, ankle or leg if you have diabetes, when the foot care team can be rung too. NHS 111 that day is the route for a badly swollen knee, and after an injury for any other joint that swells large and tight within two hours or so, or for swelling or bruising that is large or still getting worse. A joint that swells and turns warm on a blood-thinning medicine goes through NHS 111 or to A&E; with a bleeding disorder, a painful or swollen joint is one to ring your haemophilia team about first. A new red, painful eye, or a change in your sight, needs an eye casualty or urgent eye clinic the same day; in pregnancy, any change in sight, blurring or flashing lights among them, is also for your midwife or maternity unit straight away, since it can be a sign of pre-eclampsia. Where none of that applies, a GP within days is the pace for a soft, swollen joint that no injury explains and that a week or two has not settled, for soft swelling in small joints of a hand or foot or in more than one joint, for a whole finger or toe that has swollen, for swelling with more than half an hour of morning stiffness, and for a joint whose swelling is getting worse or keeps coming back. Other swelling you cannot explain that has not gone in a few days can go to a routine GP appointment, and so can a lump you cannot explain, sooner if it is growing or is hard and fixed, and swelling with pain at night or at rest, unexplained loss of weight, or a cancer in the past should be shown to a GP promptly. Swelling from a minor sprain that is already going down can be looked after at home, and shown to a GP if a fortnight passes without improvement. No referral is needed for a specialist assessment, and in this practice next-working-day appointments can almost always be arranged, and same-day appointments are sometimes possible.