What should I do about an injury that caused knee swelling and a low fever?

Kelly J. Hendricks, MD
Orthopedic Surgery
Call a doctor if you have persistent swelling and warmth in a knee joint. The knee should be checked by a healthcare professional who has experience in both the anatomy and physical examination of the knee. 
Eric W. Porritt, DO
Orthopedic Surgery
Many injuries may cause mild to moderate swelling however it should not cause a significant fever as one thinks about for an infection or illness. Any time a patient has joint swelling and a temperature of 101.4 or greater, they should be checked out by their physician.
Anthony L. Komaroff, MD
Internal Medicine
You should see a doctor right away.

Your knee swelling could be due to hemarthrosis, which means bleeding into a joint. The most common cause is an injury. It can also occur in people who take blood thinners or whose blood does not clot well.

Most people with hemarthrosis have no fever. But blood in the joint can cause inflammation and that can occasionally cause a low grade fever.

Your injury could also have torn cartilage or ligaments or even created a fracture.

Other possible causes of knee swelling and fever include:
  • Gout — crystals of uric acid form in the joint
  • Pseudogout — calcium crystals form in the joint
  • Infection — bacteria or other microorganisms get into the joint through the blood or skin; an infection seems unlikely given your description of your injury
Because each of these can be associated with fever, I doubt that it's a coincidence that you developed a fever just after your injury.

The best way to identify the cause of your joint swelling and fever is to have a sample of joint fluid removed and tested for the presence of crystals and infection. In addition, routine testing would determine the number of red blood cells (which can indicate bleeding) and white blood cells (which can indicate inflammation or infection).

Your doctor may advise one of these treatments. An anti-inflammatory such as ibuprofen (Advil, Motrin, or others) can reduce pain, inflammation and fever, but it may cause more bleeding. Acetaminophen (Tylenol or generics) may be a better choice, at least until the cause is determined. Other treatments depend on the results of additional testing, and may include a cortisone injection or antibiotics.
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Bone & Joint Injuries

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Often caused by falls, trauma, or injury, bone and joint injuries can sometimes be serious enough to require surgery. A broken bone can occasionally puncture your skin, causing intense pain. If you suspect that you have a broken b...

one, you will need medical treatment right away. In serious cases, pins, screws, and plates are placed into the body to stabilize the bone and help it heal. Joints connect our bones, and joint injuries can often occur in the elbows and knees. To reduce your risk of joint injury, stay healthy. Staying at a healthy weight and keeping your muscles strong and fit reduces the wear and tear on your joints.

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.