Infectious Causes of Arthritis: Sepsis and Lyme

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  • 0:09 Infectious Causes of Arthritis
  • 0:33 What Is Septic…
  • 3:10 Diagnosis and…
  • 4:30 Lyme Arthritis
  • 5:35 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

This lesson will discuss septic arthritis and how Lyme disease may play a role in the development of arthritis. We'll talk about the ways septic arthritis may be diagnosed and treated.

Infectious Causes of Arthritis

Arthritis is an inflammation of the joints that can be caused by a huge variety of factors. Everything from genetics to immune-mediated diseases to trauma may cause arthritis. I think if you cough you might get arthritis, but I exaggerate. This lesson will discuss two more forms of arthritis that have less to do with genetics and more to do with infectious causes.

What Is Septic Arthritis and Why Does It Occur?

One of the worst forms of arthritis you can ever get is known as septic arthritis. This is the inflammation of a joint caused by an infectious agent. If left untreated, septic arthritis can even lead to sepsis, a condition where an infectious agent causes a body-wide, life-threatening, inflammatory reaction.

There are mainly two ways that an infectious agent, most commonly a bacterium, may cause an infection in your joint. You can imagine the first cause of infection by picturing yourself running around like crazy, jumping up and down, playing some kind of game on the field, and you end up injuring yourself to the point of receiving a penetrating trauma right into your knee.

Let's say you were running to catch a football, jumped for the ball, and managed to get a sharp stick lodged in your knee. I mean, that's painful enough. But, the problem is that the stick has a ton of germs on it, and those germs will giddily jump off of the stick and into your joint even if you remove the stick.

Another way the trauma can introduce an infection into your joint has nothing to do with dirty sticks. It has to do with dirty surgical instruments. Again, let's say you were playing that same game of football, and you twisted your knee so badly that you needed surgery. Even though your injury didn't break your skin, the surgical instruments used in the surgery will have to. If they were improperly sterilized, so that even one little germ remains on it, the surgeon may iatrogenically introduce an infection into the joint. An iatrogenic infection is an infection inadvertently caused by a physician during the course of their diagnostics or treatment.

So, trauma is one way to get septic arthritis. The other way to get septic arthritis is by way of a generalized, body-wide infection. For example, you may have a bacterial infection in one part of your body that gets out of hand and moves into your bloodstream and travels to your joints to cause septic arthritis. In fact, the most common cause of septic arthritis is caused by a bacterium called Staphylococcus aureus.

In either case, whether trauma or spread through the bloodstream, septic arthritis is a super big medical emergency. While non-septic forms of arthritis, such as osteoarthritis, may take years to destroy a joint, the infectious agents of septic arthritis cause such severe inflammation that your joint will be destroyed irreversibly in a matter of just days.

Diagnosis and Treatment of Septic Arthritis

The joints that are affected are typically swollen, painful, and red. A fever, something not seen in cases of non-septic arthritis, may present since you know that a fever helps to fight off infection. Therefore, if you have a fever combined with a swollen joint after a penetrating injury, you might want to see a doctor immediately.

Besides looking for the clinical signs and symptoms I outlined, another very telling way to diagnose septic arthritis is by taking an aspirate, a little sample by way of syringe and needle, of some joint fluid. In cases of an infectious cause of arthritis, there will be tons of white blood cells in the joint when there should be virtually none. Those white blood cells are the things that try and kill off the infection. So, if you see a lot of white blood cells in a joint, then you know it's infected, kind of like if you see a traffic light turn yellow, then you know it's going to be followed by a red light. One follows the other just like lots of white blood cells inevitably follow an infectious agent around.

Once diagnosed, the infected joint fluid must be removed immediately by a needle or surgical drainage. In addition, antibiotic therapy, the drugs that kill bacteria, must be used if the septic arthritis is caused by a bacterium.

Lyme Arthritis

Now, before I let you go, I want to mention one thing. Physiology and medicine are always full of exceptions to virtually every rule. This lesson is, unfortunately, also no exception. While typically infectious causes of arthritis cause a rapid onset of clinical signs after infection, that doesn't always have to be the case.

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