Joint Infection

The protocol for Joint Infections:

Joint Infection


Let’s break it down!


Joint infections (aka septic arthritis) aren’t a super common chief complaint; only about 2-5 cases per 100,000 people.  In addition, 87% of those who do have septic arthritis also have 1 other predisposing medical condition (cancer, renal disease, etc.) and most soldiers don’t necessarily fit that description.  Regardless, joint pain in itself is extremely common and if there is one thing you take from this lesson it’s that all joint pain is a joint infection until proven otherwise.

Joint infections can infect any joint in the body: wrists, shoulders, elbows…..but the majority (50%) occur in knees.  It’s important that you ask about any recent procedures or breaks in the skin that may have caused the infection (bites, punctures, etc.), but the most cases of septic arthritis are the result of hematogenous seeding, which is when an infection from some other part of the body (Ex. lungs)  travels through the blood and settles into a distant joint.

For a more in-depth look at septic arthritis, check out the video below: 

This one is easy.  We’re looking for a red, hot, painful joint! The only way to definitively diagnose a septic joint is with an arthrocentesis (sticking a needle in a joint) to collect a sample of the infected synovial fluid and have it examined in a lab.  But of course, we’re not likely to have this capability in our setting, so clinical judgment is going to be enough for us to treat this patient.

The pictures below show some classic cases of septic joints:

Screenshot 2020-02-17 at 1.53.22 PM









1. Immobilize joint
Immobilization has long been recommended for analgesic purposes, but concern has been raised about the effect of immobilization on the recovery of cartilage in the joint.  Evidence shows that simply limiting movement, as opposed to full immobilization, maybe the best way to go.

2. Administer ONE of the following: Ertapenem or Ceftriaxone
Most cases of septic arthritis are caused by Staphylococcus aureus (40%), but it can be caused by any number of bacterial organisms. Given the variety of potential organisms and the lack of diagnostic equipment in the field, we’re going to hit them with heavy broad-spectrum antibiotics.  Ertapenem is still good, but Ceftriaxone seems to be more favorable in recently published guidelines.

3. Treat per Pain Management protocol
Joint infections are quite painful.  Although many ER doctors are able to discharge these patients with NSAIDs after treatment, you may want to consider short-term opiates during any sort of evacuation if the ride is going to be bumpy.



Joint infections can be alarmingly dangerous.  They carry a mortality rate of 15% for patients undergoing treatment and 66% for those without treatment. Given the mortality and the fact that these patients almost always require arthrocentesis or surgery to drain fluid from the joint, a Priority evacuation is warranted for all cases.


Till Next Time!



Brandon Simpson, PA-C
Follow me
Latest posts by Brandon Simpson, PA-C (see all)