Red Flags After Total Knee Replacement: What to Watch Out For
May, 21 2025
Your new knee should help you move better, not leave you wondering if something just went off track. After surgery, not every ache or weird feeling is a big deal—bruising and swelling are pretty normal. But some signs are your body’s way of waving a red flag, and you’ll want to know what those look like, fast.
If you’re stuck with pain that doesn’t ease up, or suddenly gets worse, don’t just grit your teeth and hope for the best. Some swelling after a knee replacement is expected, but if it balloons or gets hard and hot, that’s not business as usual. And if your skin starts changing color or you spot any drainage from the wound, that’s your cue to pay attention.
Getting the hang of recovery means knowing what’s normal and what isn’t. It’s your body, and you know when something feels off. Keep reading for the exact stuff you should watch for, and when it’s time to call your surgeon instead of waiting things out.
- Pain That Doesn't Quit or Gets Worse
- Unusual Swelling or Stiffness
- Signs of Infection You Shouldn’t Ignore
- Trouble Moving or Bearing Weight
- Abnormal Bruising or Changes in Skin Color
- Tips: When to Call Your Surgeon and What to Say
Pain That Doesn't Quit or Gets Worse
Pain is expected after a knee replacement, but there’s a difference between the normal post-surgery discomfort and pain that’s a big red flag. Right after surgery, most people rate their pain between 6 and 8 out of 10, but this should start dropping within a few days. If you notice your pain isn’t improving, or suddenly ramps up after feeling better, don’t brush that off.
So what’s normal? Achy or stiff feelings, especially when you first get moving, are common. Your knee might grumble with activity for weeks. But pain that keeps you up at night, makes you sweat, or interferes with walking, is a warning sign.
- If your pain is as bad—or worse—than it was before surgery, that's not standard recovery.
- If pain becomes sharp, stabbing, or keeps spreading rather than staying around the knee, get it checked.
- If you need more and more pain meds to stay comfortable, or you suddenly can’t manage the pain, that’s a problem.
Ignoring ongoing severe pain puts you at risk for big complications, like deep infection or hardware issues. Here’s what the numbers look like for pain after knee replacement:
| Days After Surgery | Typical Pain Score (0-10) |
|---|---|
| Day 1-2 | 6-8 |
| Day 3-7 | 4-6 |
| Week 2+ | 2-4 |
If your pain is getting worse or stuck at the higher end after the first week, something is off. The main thing is to pay attention and speak up. Your doctor is used to these questions. If you feel you’re not bouncing back, or if the pain is surprisingly intense, call your clinic. Catching problems early can keep a minor hiccup from turning into a major knee replacement complication.
Unusual Swelling or Stiffness
Right after knee replacement surgery, some swelling is completely normal. Your body’s just reacting to the trauma of surgery and the healing process kicking in. But here’s the thing—if your knee suddenly swells way more than before, especially after the first week, or gets super stiff so you can’t move it well, that’s a red flag.
If the swelling is so bad your skin is shiny, hot to touch, or feels super tight, don’t just wait it out. Excess fluid, especially if it comes on fast, could mean infection or a blood clot. Blood clots aren’t super common, but they are serious and need fast treatment.
You should also pay attention to stiffness that doesn’t budge. Most folks start bending and straightening their knee bit by bit with physical therapy. If you’re stuck at the same angle for days or weeks no matter how much you try, or pain shoots up when you try to move, something’s up. Scar tissue might be building up, or swelling could be jamming things up more than it should.
Here’s what action to take if you spot these red flags:
- Measure the swelling: Compare both knees. If the new one is noticeably larger and it isn’t getting better, snap a photo and keep track over a few days.
- Watch for other symptoms: Hot, red, or super stiff knee? Trouble walking or sharp pain? Those shouldn’t be ignored.
- Call your doctor if: The swelling suddenly spiked, your knee is super stiff, or you spot redness and heat along with the swelling.
Don’t tough it out. If the swelling or stiffness gets worse instead of better, or changes quickly, get in touch with your care team. They’d rather you check in than risk something serious brewing under the surface.
Signs of Infection You Shouldn’t Ignore
An infection after a total knee replacement isn’t something to brush off. Even though it’s not super common (the rate is about 1-2% after this type of surgery), it can mess up your recovery if you don’t spot it early. Here’s what you need to keep an eye out for:
- Redness and heat: If the skin around your knee turns bright red or feels hot, your body might be fighting an infection. A little pinkness is normal right after surgery, but if it’s getting worse or spreading, that’s a problem.
- Pus or unusual drainage: Clear fluids are okay, especially in the first few days. Yellow, green, or cloudy pus coming out of your knee? That’s a red alert. Also, a bad smell is not normal.
- Fever and chills: If your temperature jumps above 100.4°F (38°C), don’t wait it out. Chills, sweating, or feeling weirdly weak or lightheaded can be signs the infection is spreading in your body.
- Pain that keeps getting worse: Some discomfort is normal. But if the pain ramps up instead of getting better and comes with other signs, it’s time to call the doctor.
Just so you get a clearer picture, check out this list of normal vs. not-normal signs after a knee replacement:
| Normal Signs | Worrisome Signs |
|---|---|
| Mild swelling, bruising, or warmth | Increasing redness, hot skin, pus/drainage |
| Low-grade fever (below 100°F/37.8°C) right after surgery | Fever over 100.4°F/38°C, chills, night sweats |
| Aching that gradually improves | Pain that’s getting worse after a few days |
If you spot any of those worrisome signs, don’t wait for your next check-up. Call your surgeon’s office or your hospital’s after-hours line. Waiting can make things harder to treat and lead to bigger problems, so it’s much better to play it safe.
Trouble Moving or Bearing Weight
You should expect your knee to feel stiff and weak for a while after surgery, but being totally stuck or unable to put weight on your leg is not on the menu. Physical therapy is supposed to be tough, but it’s there to help you regain movement step by step. If you suddenly can't move your knee or walking becomes impossible, that’s a red flag you can’t ignore.
Here’s the deal: it’s normal to need a walker or cane at first. But you should see steady improvement each week. A backslide—like not being able to straighten your leg or put pressure on it after some progress—is cause for concern. Sometimes, these problems show up as your knee locking up, buckling, or giving out. That’s not just annoying; it can mean something serious like a blood clot, joint infection, or even a problem with the implant.
- If you feel sudden, severe pain with movement, stop and check for swelling, redness, or warmth.
- Dramatic loss of motion, like frozen knee, needs a quick check by your doc.
- If you hear or feel a pop while moving and then can’t support your weight, don’t try to tough it out—call your surgeon right away.
Doctors expect some ups and downs during knee replacement recovery, but according to a 2023 review in "The Journal of Arthroplasty," less than 3% of patients develop severe mobility issues after surgery—and most serious problems show up in the first two months.
| Red Flag | What It Might Mean |
|---|---|
| Sudden inability to move knee | Possible joint infection or mechanical issue |
| Knee gives out unexpectedly | Nerve problem or issue with implant position |
| Can't put weight at all | Fracture, major blood clot, or severe infection |
If anything here rings true for you—especially if you’re losing ground instead of gaining it—don’t wait to check in with your medical team. The faster you find the problem, the quicker you can get back on track.
Abnormal Bruising or Changes in Skin Color
Bruising is a normal part of knee replacement recovery. You might spot some purple or yellow marks around your knee, thigh, or even down your shin in the first 2-3 weeks. This usually fades on its own. But things change if you notice new or spreading bruises, or if your leg looks red, bluish, or unusually pale.
If your leg turns bright red or feels hot and tight, especially near the calf, it could mean a blood clot—doctors call it deep vein thrombosis (DVT). If the skin goes cold, looks very pale, or bluish, that might mean not enough blood is getting to your leg. All these signs are a reason to get checked quickly, because some complications can turn serious fast.
"Large or worsening bruising, especially if it's accompanied by swelling, pain, or heat, should prompt a call to your surgeon. Changes in skin color—especially red, purple, or pale areas—are never something to ignore after surgery."
— American Academy of Orthopaedic Surgeons
Here’s what to keep your eyes out for:
- Bruises that don’t fade after three weeks, or suddenly get bigger
- Redness that spreads, especially up or down your leg
- Leg turning blue, purple, or looking much lighter compared to the other
- Cool skin or numbness below your knee
- Accompanying swelling or pain that’s getting worse, not better
Just to give you an idea—DVT after knee replacement happens in about 1% to 2% of cases, but doctors are always on alert because it can be dangerous if missed.
| Warning Sign | What it Might Mean | What to Do |
|---|---|---|
| Red, hot, swollen calf | Possible blood clot (DVT) | Call your doctor right away |
| Bluish or pale skin | Poor circulation | Needs medical attention |
| Bruises that keep spreading | Bleeding problems | Get checked if not fading |
If you spot any of these, grab your phone and get advice from your doctor. Quick action can save a lot of trouble—and possibly a lot more.
Tips: When to Call Your Surgeon and What to Say
Lots of folks worry about bugging their surgeon after a knee replacement, but catching something early can save you way more hassle in the long run. If something feels off and you see one of the red flags—don’t put off making a call.
Here’s when you need to pick up the phone right away:
- Severe pain that doesn’t get better with prescribed meds
- Fever over 101°F (38.3°C) or chills—these aren’t normal during recovery
- Redness, warmth, or oozing pus at the incision
- Sudden, severe swelling or the knee feels hard and hot
- Trouble moving your foot or toes, or numbness that won’t go away
- Shortness of breath or chest pain (head straight to the ER for those)
When you call, be clear and specific so your surgeon or nurse knows what’s going on. Here’s what you should have on hand before dialing:
- Details about your symptoms: when they started, how bad they are, if they’re getting worse
- Your temperature, if you have a fever
- Any new meds you’ve started or stopped
- Photos of your incision (these can be super helpful for the doctor to see what’s going on)
It helps to use plain language: “My knee is more swollen and painful than it was yesterday. The redness has gotten worse, and I noticed yellowish drainage.” You don’t have to impress anyone with medical terms—simple and direct works best.
Wondering what happens if you wait too long? Studies say infections that get caught early have a way better shot at being fixed without more surgery or a longer hospital stay. Check out this quick comparison:
| Red Flag | Time to Act | Possible Outcome |
|---|---|---|
| Rising fever or pus | Call same day | Short antibiotics, lower risk |
| Hot, swollen knee | Call same day | May prevent major complications |
| Too much pain or loss of movement | Call within 24 hours | Quick care can protect joint health |
If you’re not sure, trust your gut. It’s always better to be safe than sorry when it comes to your new knee. Surgeons would rather you call early than miss something important.