Why Is My Knee Swollen, Warm or Painful?
A swollen knee is a sign that something is irritating or inflaming the joint. The cause can be wear-and-tear, crystals, inflammatory arthritis, injury or, rarely, infection.
The knee is the largest joint in the body and one of the most common places for swelling. Swelling usually means extra fluid inside the joint or a thickened joint lining. Warmth and redness suggest active inflammation.
What your knee swelling may mean
Start with one question: did the swelling follow an injury? Swelling within hours of a twist or fall suggests a ligament, cartilage (meniscus) or bone injury. Swelling without any injury points more towards arthritis, crystals or infection.
Other useful details for your doctor:
- Did it come on suddenly, over hours, or slowly over weeks?
- Is the knee warm or red, and do you have a fever?
- Have other joints been swollen, now or in the past?
- Has the same knee swollen before?
Why does my knee hurt at night?
Knee pain at night can come from advanced osteoarthritis, inflammatory arthritis, gout, or problems around the joint such as bursitis. Pain that wakes you regularly, comes with swelling, or occurs with weight loss or fever is not typical wear-and-tear and needs proper evaluation. A rheumatologist can examine the joint and order targeted blood tests and imaging.
Mechanical or inflammatory?
This table shows how mechanical knee pain usually differs from inflammatory knee pain. Some people have both.
| Feature | Mechanical (wear-and-tear or injury) | Inflammatory (arthritis or crystals) |
|---|---|---|
| How it starts | Gradually with age, or suddenly after an injury | Over hours (crystals) or weeks (inflammatory arthritis), without injury |
| Swelling | Mild, or after activity; hard bony edges | Soft, warm, often obvious swelling |
| Warmth and redness | Usually none | Common |
| Stiffness | Short, under 30 minutes | Longer, often over 30 minutes |
| Pain pattern | Worse with walking, stairs or squatting | Present at rest and at night as well |
| Other joints | Usually the knee or hip only | Other joints may be swollen too |
A hot swollen knee: crystals or infection?
| Feature | Gout | Pseudogout (CPP crystals) | Septic (infected) arthritis |
|---|---|---|---|
| Urgency | Prompt treatment | Prompt treatment | Emergency: same-day assessment |
| Cause | Uric acid (urate) crystals | Calcium pyrophosphate crystals | Bacterial infection inside the joint |
| Typical person | Men from their 30s; women usually after menopause | Mostly adults over 60 | Any age; higher risk with diabetes, RA, older age, recent joint injection or surgery |
| Fever | Possible | Possible | Common, but no fever does not rule it out |
| Key test | Joint fluid examined for crystals and infection; both can be present together | ||
Sources: 2020 ACR gout guideline; NICE NG219; NHS septic arthritis. Reviewed by Dr. Jyoti Ranjan Parida, DM (Rheumatology), October 2026.
Common causes of knee pain with swelling
- Osteoarthritis: the most common cause of knee pain in older adults. Flares can cause swelling.
- Gout: uric acid crystals can cause a sudden, very painful, swollen knee.
- Pseudogout (CPPD): a different type of crystal, more common after 60.
- Rheumatoid arthritis and psoriatic arthritis: usually with swelling in other joints as well.
- Reactive arthritis: joint swelling a few weeks after a bowel or urinary infection.
- Injury: ligament or meniscus tears, usually after a twist or fall.
- Bursitis: swelling in a fluid sac in front of the kneecap, often from kneeling.
- Septic arthritis: infection inside the joint. Rare, but an emergency.
When is it urgent?
Get same-day medical help if: your knee is suddenly hot, red, swollen and very painful, especially with fever or feeling unwell (possible septic arthritis); you cannot put weight on the leg after an injury; or your calf or whole leg is swollen and painful. Call +91 93386 53086 during clinic hours (Mon–Sat, 9 AM–2 PM & 4:30–9 PM). Outside clinic hours, or if symptoms are severe, go to the nearest emergency department straight away.
Which doctor should you see?
- Swelling without injury, warmth, or swelling that keeps coming back: see a rheumatologist, ideally one who can test the joint fluid. At OARC, Dr. Jyoti Ranjan Parida (Saheed Nagar) or Dr. Debashis Maikap (Sailashree Vihar).
- Knee pain worse with walking and stairs, age 45+: often osteoarthritis. A physician or rheumatologist plus physiotherapy is a good start.
- Swelling after a twist or fall, or a knee that locks or gives way: an orthopaedic surgeon. OARC does not offer orthopaedic surgery; we refer when needed.
When to book an appointment
Book an appointment if your knee has been swollen for more than a few days, if swelling keeps coming back, or if you have pain and swelling in other joints too. Avoid relying on painkillers for weeks without a diagnosis.
A swollen knee has a cause that can usually be found. Our rheumatologists can examine the joint and arrange tests.
Knee pain and swelling: common questions
See a rheumatologist in Bhubaneswar
OARC has two centres in Bhubaneswar, with an in-house lab, Immunix Labs (working with NABL-accredited partner labs), pharmacy, imaging and physiotherapy. Bring any previous reports, X-rays or scans and a list of your current medicines.
Saheed Nagar (Main Centre)
Dr. Jyoti Ranjan Parida consults here
A/90 Saheed Nagar, opp. Ayakar Bhavan, Bhubaneswar 751007
Mon–Sat 9 AM–2 PM & 4:30–9 PM · Sunday closed
Sailashree Vihar, Chandrasekharpur
Dr. Debashis Maikap consults here
P-13/14 Sailashree Vihar, Chandrasekharpur, Bhubaneswar 751021
Mon–Sat 8–9 AM & 5–6 PM · Sunday closed
References
- NHS. Knee pain. NHS website. www.nhs.uk/symptoms/knee-pain/
- NICE. Osteoarthritis in over 16s: diagnosis and management (NG226), 2022. www.nice.org.uk/guidance/ng226
- FitzGerald JD, et al. 2020 American College of Rheumatology Guideline for the Management of Gout. Arthritis Care Res 2020;72:744–60. doi.org/10.1002/acr.24180
- NICE. Gout: diagnosis and management (NG219), 2022. www.nice.org.uk/guidance/ng219
- NHS. Septic arthritis. NHS website. www.nhs.uk/conditions/septic-arthritis/
This page gives general information and is not a diagnosis. Please see a doctor about your own symptoms. Read our editorial policy to learn how we write and review medical content.