What is an infected knee?
An infected knee may be a skin infection (cellulitis) or a more serious infection in the joint (septic arthritis).
Quickcare or ER?
Red flags that will send you to the ER.
- Severe pain
- Also, if you Cannot walk, you need to go the ER
Remember, an infected knee joint is a true emergency. In the knee joint, when bacteria fight with cartilage, bacteria will win. The cartilage will get damaged.
What will the doctor ask?
Your doctor will want to know your symptoms.
Remember, a symptom is your description of your condition to your doctor. It is your story
Answers to the following questions will help:
When did it start?
What makes it better?
What makes it worse?
How bad is the knee pain?
Is the pain sharp or dull?
Are you able to walk?
Do you have any associated symptoms such as fever, numbness ?
On point for the doctor to know is a major surgery such as a knee replacement had preceded the infection.
A doctor will do an exam to look for signs.
Remember, signs are objective findings that doctors finds on examination
As a doctor, I will look for swelling and redness. If the infection is simply in the soft tissue, a sigh of relief is felt. I will look to see if there is a fever.
Also, can the patient walk on it?
How much movement is in the joint? Your doctor will try (gently) to bend the knee.
What is the doctor thinking?
To explain the signs and symptoms, your doctor will develop a differential diagnosis. This is list of possible reasons for the knee infection.
Two questions need to be answered.
#2. The next point is the location of the infection. Is it on the skin or in the joint.
How do you know? THIS IS KEY!
It has been my experience that a patient can walk with just the skin infected.
When it is in the joint, then it is hard to bear weight. It is hard to bend. Patients look sicker.
Fever may present itself in either scenario.
One consideration for your doctor is sickle cell disease. Seen largely in patients of African descent, sickle cell disease should be a differential diagnosis for African-American children with fever and knee pain.
What is the treatment of a hot knee?
With an infection of the skin then simple antibiotics like Keflex or Bactrim (for MRSA) are prescribed.
However, if the infection is in the joint, most docs would want to “tap” the knee. This means, put a needle into the joint space and take out the fluid. The analysis can take days. The intention is to look for bacteria growing in the knee joint.
So antibiotics are given right away to cover for the possibility of an infection. Many times an infected knee will need to be opened up and washed out under the care of a bone doctor (orthopaedist).
At times it will be difficult to know if the red, hot knee is an infection or arthritis. Since there is an unknown and lab results can take days, it is best to cover with an antibiotic. Sickle cell patients characteristically get an associated osteomyelitis due to the salmonella bacteria.
As mentioned, the lab result ( the fluid aspirated from the knee) may take days.
With an infection then white cells are present. With arthritis, crystals are present.
If the infection eats away at the cartilage, it is possible that a remedy may be a knee replacement (also known as TKA-Total Knee Arthroplasty).
How long will you be sick?
Sometimes it is long haul with an infection.
A skin infection will generally last a week.
A joint infection can be a much longer recovery. Bacteria mixed with cartilage is a bad combination.
Let me tell you a story
Once there was a young man named Hardeep who said that he could not walk. He said to me, “Dude. I mean ‘Doc’ I mean ‘Dude Doc’ You gotta help me. I’m dealing with some serious pain.” He hobbled into the clinic. Hardeep was way too young to need the help of a cane. He never did fall but he thinks he bumped it. When? How? After way too many beers at the ball game, the details are kind of fuzzy. He just said it was red and swollen and it hurts when he walks.
It turns out the pain is local, sharp, gets better when he rests and worse when he walks. It is associated with a fever and general malaise.
Since Hardeep had difficulty walking on it, then it could be a knee joint problem. Not good. I sent him to the ER, where the joint was aspirated. Pure pus.
IV antibiotics were administered followed by a orthopedic consult.
I hope this helps