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Septic Arthritis

Septic arthritis is an uncommon medical problem, but of course it can be very serious. I’m always impressed by the low incidence of septic arthritis and infected joint. I think if you walk through any hospital, you look at all the patients that have bacteremias, all the patients that are immunosuppressed, whether it’s chemotherapy, steroids, transplant, all the patients in the intensive care units with lines going in and lines going out and still you see a septic arthritis patient once a month. That’s a pretty good number. I think it’s because the joints are somehow naturally protected against infection, but because it is a closed space infection and it may occur in patients that are otherwise debilitated.

I like to consider septic arthritis a medical/surgical emergency. Surgeons being the orthopedic surgeons. In my experience - and I may have made a couple of cracks about orthopedic surgeons, and that’s very common that rheumatologists do that, and I guess internists and family practitioners do that - but I get along very well with my orthopedic colleagues.

When I see a patient with a septic joint, unless it’s gonococcal disease - which is much less virulent - I like to have the surgeon see the patient at least within the first 24 hours. If it’s like 6 o’clock on a Friday I might just say, "Could you stop in tomorrow morning when you are making rounds?" And the reason is, because occasionally these patients do need surgical intervention and I think it’s easier for a physician to get a feel for what’s going on if they have been following the patient, rather than after five days of continuous fevers and inability to aspirate the joint, to call the surgeon and say, "Look, I think the patient needs an operation." They are not going to have a good feeling about what’s going on in that patient, what is the general medical state with the patient.

Now septic arthritis is usually due to hematogenous spread of bacteria from somewhere else. Depending on the bacteria, it will tell you which site. Staph is probably the most common. Usually the skin, particularly in rheumatoid or diabetic patients where they get a lot of skin ulcerations or break down, but also soft tissues and obviously endo-vascular, endocarditis but also catheters that get infected and the like. Gonococcus, usually from venereal source, either the GU tract, rectum or the throat, depending on the sexual practices of the patient. And so on and so forth, depending on which bacteria it is, this is where these things usually come from. It’s very rare to have contiguous spread from the soft tissues into a joint, or from an osteomyelitis.

Basically the damage that occurs in septic arthritis is due to two things: bacterial products - bacteria like to make all kinds of toxins, exotoxins, endotoxins, hemotoxins, whatever - but just the fact that there is dead bacteria around attracts these lovely cells called neutrophils. Normally they are very useful but in a closed space infection.

If you look at a patient with septic arthritis, there are a couple of rules to remember. Typically it is a monarthritis, particularly in staphylococcal infection. More often involves weight-bearing joints and it’s not clear why. Maybe the joints are just bigger. There’s more blood flowing through them and it’s more likely that a bacteria will get stuck there. However, gonococcal disease and sometimes streptococcal disease may present as a migratory polyarthritis, and that’s important to remember. The patients may have had symptoms in one or two joints before.

For gonococcal arthritis, there are two things that you might see that are helpful. One is this vesicular pustular rash. This is one that is sort of in the healing phase. Generally, this occurs during the bacteremia, so a lot of times when the patient comes in with the arthritis this is starting to heal. So I ask the patient, "Did you have any pimples on your arms or legs?" because that’s where they are usually found, the distal extremities. They might point out a little lesion that looks like a tiny scab, that’s all that is left. This is a little bit fresher and you can see its erythematous base with this yellow pustule. If you were to scrape - and I recommend using gloves if you are going to do this - scrape and make a slide you could find the bacteria on gram stain. Although it’s usually not possible to culture from this because the bacteria is almost always dead.

Now again, as I’ve mentioned, often you’ve done your workup, your gram stain is negative, you have your cultures cooking but you suspect your patient has a septic arthritis. If the patient is already in the hospital, great, if not, you are going to have to admit them and start them on IV antibiotics. And you are going to guide your therapy in using your epidemiologic and demographic information. Similar to tables that you can find in textbooks for meningitis and osteomyelitis, septic arthritis does tend to occur associating age with bacterial etiology. So the very young children, you have to worry about staph, strep and H. flu. Once the patient has been exposed to H. flu, or as is the case with most kids - I think about 18 months, maybe the family practitioners can tell me, or so - you get your Hemophilus vaccine. So once that occurs then the incidence almost disappears. You can still see staph and strep in older kids. Now the young to middle aged adults, still a little bit of staph but most of those are patients who are so predisposed. You can see a very large predominance of gonococcal arthritis. Then in the older-aged patients, the recurrence of the staph and also, depending on their underlying medical state, maybe some gram-negative rods and other more virulent, opportunistic types of organisms. So using that information you can sort of pick your antibiotics.

I used to have a slide that gave the specific antibiotics, but the antibiotics change and of course every institution has different sensitivities, you just have to use the information - usually every microbiology lab has a sensitivity table and your infectious disease colleagues can certainly assist you in picking the appropriate antibiotic.