When to Call After a Knee Replacement
Which symptoms after a knee replacement need a phone call today, which need an ambulance, and which look alarming but are an ordinary part of healing — including the signs of infection and of a clot, set out plainly.
Most of what worries people after a knee replacement is ordinary. The bruise that spreads to the ankle, the knee that feels hot, the swelling that comes back after a big day — these are healing, not complications.
A small number of things are different, and they are worth knowing by name, because the two that matter most are both treated far more easily when they are caught early.
This page sorts them by what to do, not by how frightening they sound.
Call 000 for sudden shortness of breath or chest pain.
Phone the rooms on (08) 6332 6365 the same day for fever or chills, redness or heat spreading outwards from the wound, discharge coming through the dressing, pain that is escalating rather than easing, or new calf pain, tenderness or swelling on one side.
Raise it at your next appointment for everything else that is bothering you but not changing quickly.
The emergency, and why it is on this list
A clot that forms in the leg can travel to the lungs. That is uncommon, it is the reason for the clot prevention you were given, and it is the one thing on this page that should not wait for a phone call to the rooms.
Sudden shortness of breath, or chest pain that is worse when you breathe in, means calling 000. Not the rooms, not the GP, not the morning. An ambulance.
You are not expected to diagnose it. Breathlessness that arrives suddenly and has no obvious explanation is enough.
Infection: it is the pattern, not the sign
Almost every individual sign of infection also occurs in normal healing. A new knee is warm. A wound is pink along its edges. Aching at night is routine. Looking for any one of those on its own will only frighten you.
What distinguishes an infection is the direction of travel.
- Pain that increases after a period of improvement. This is the single most useful signal. Pain that has never fully settled is common. Pain that was getting better and then started getting worse is the pattern worth a phone call.
- Fever or chills, or simply feeling unwell in a way that is out of keeping with the rest of your recovery.
- Redness spreading outwards from the wound, rather than sitting along the line of it.
- Fluid or discharge coming through a dressing that had been dry. A wound that seals and then starts weeping again has changed.
Any of those is worth a call the same day. Infection identified early has materially more treatment options than infection identified late, and that difference is large enough to make a phone call about a false alarm a good trade every time.
An infection can also arrive long after the surgery, when bacteria reach the joint through the bloodstream from a dental abscess, a skin infection or a urinary infection. A knee replacement that becomes newly hot, swollen and painful years later still warrants review.
Clots: the calf is what you are watching
Some swelling through the whole leg is expected. A calf that becomes distinctly painful, tender, firm or warm — and noticeably different from the other side — is not.
The useful comparison is your own other leg, and your own leg yesterday. New, worse, one-sided: any of those three is a reason to phone rather than wait and see.
Keep taking the clot prevention for the full course you were given, even once you feel well. The risk does not end when the pain does, and stopping early is one of the more common avoidable problems.
What looks alarming and is not
These are the things the rooms hear about most often, and they are all ordinary.
- Bruising down the calf, ankle and foot. Blood released during the operation tracks downwards under gravity. It often appears days later, looks dramatic, and fades through several colours. Discolouration alone is not a clot — pain and tightness in the calf are.
- A knee that feels hot. A new joint runs warm to the touch for months.
- Swelling that comes back. Most settles over six to twelve weeks, but mild swelling after activity can continue for six to twelve months. It tracks what you did yesterday.
- Clicking or clunking. Metal and plastic articulating are not silent.
- A patch of numbness beside the scar, usually on the outer side. A small nerve to the skin is almost always cut during the approach. It is expected, and for most people it shrinks over the year.
- Small blisters where a dressing has pulled against swollen skin.
- Feeling flat. Common in the first weeks and not a complication, though the emotional side of recovery is worth reading if it is persisting.
Photograph it
For anything involving the wound, take a photograph in good natural light before you phone. It is easier to describe a wound with a picture in front of you, and it gives the rooms something to compare against at your next review.
On phoning about nothing
The rooms would much rather field a call about a normal bruise than hear about an infection a fortnight after it started.
Most of these calls end in reassurance. That is the system working, not a waste of anyone’s time. The people who come to harm are not the ones who phoned too early.
If you are Dr Clark’s patient and something has changed, phone the rooms on (08) 6332 6365. If it is sudden breathlessness or chest pain, call 000 first.
Related reading
The first two weeks at home covers the practical side of the fortnight when most of these questions arise. Knee replacement recovery sets out what the normal arc looks like week by week, and what not to do after a knee replacement covers the habits that slow recovery down.
What are the warning signs after a knee replacement?+
Phone the rooms on (08) 6332 6365 the same day if you have fever or chills, redness or heat spreading outwards from the wound, discharge or fluid coming through the dressing, pain that is escalating rather than gradually easing, or calf pain, tenderness or swelling — particularly on one side. Sudden shortness of breath or chest pain is an emergency: call 000. Phoning about something that turns out to be normal is always the right call.
How do I know if my knee replacement is infected?+
The pattern matters more than any single sign. An infection usually declares itself as pain that increases after a period of improvement, rather than pain that never settled. Look for fever or chills, feeling generally unwell, redness spreading outwards from the wound rather than sitting along it, heat, and fluid or discharge coming through a dressing that had been dry. Any of those warrant a phone call the same day, because an infection identified early has materially more treatment options than one identified late.
What does a blood clot feel like after a knee replacement?+
A clot in the calf typically causes pain or tenderness deep in the calf muscle, often with swelling, firmness or warmth that is new, worse than it was, and noticeably different from the other leg. Some swelling of the whole leg is expected after a knee replacement; a calf that becomes newly painful and tight is not. If a clot travels to the lungs it causes sudden shortness of breath or chest pain, which is an emergency — call 000.
Is it normal for the bruising to spread down to my ankle and foot?+
Yes, and it is one of the most common things people phone about. Blood that was already released during surgery tracks downwards under gravity, so bruising appearing in the calf, ankle and foot several days later is expected and is not a sign of bleeding. It often looks worse before it fades, and the colours change as it resolves. What is not expected is a calf that becomes painful and tight rather than simply discoloured.
My knee is hot and swollen — is that an infection?+
Not on its own. A new knee runs warm to the touch for months, and swelling that varies with how much you have done is an ordinary part of healing that can continue for six to twelve months. What changes the picture is the combination: heat and swelling together with fever, feeling unwell, spreading redness, wound discharge, or pain that is climbing rather than settling. A knee that suddenly becomes far more swollen, hot and painful than it was should be reviewed promptly.
Will I be wasting the surgeon's time if it turns out to be nothing?+
No. The rooms would far rather take a call about a normal bruise than hear about an infection a fortnight after it started. Most of these calls end with reassurance, and that is a good outcome, not a wasted one. If you are unsure, photograph the wound in good light and phone — a photograph often settles it quickly.
How long after a knee replacement can an infection develop?+
Most occur in the first few weeks, which is why the wound is watched closely early and why the two-week review exists. But a joint replacement can become infected much later, including years afterwards, usually when bacteria reach it through the bloodstream from somewhere else — a dental abscess, a skin infection, a urinary infection. That is why a new hot, painful, swollen knee replacement warrants review whenever it happens, not only in the weeks after surgery.