Septic Joint

It's not often considered by most patients as a site of possible infection, but a joint may become infected.  When a joint does become infected, it is known as a "septic joint" or "joint sepsis".   A septic joint is characterized by being red, hot, swollen and very painful.  The patient will usually limp noticeably to take pressure off the affected joint, and the patient may develop systemic signs of infection (fever, chills, night sweats, confusion). 

Possible alternative to diagnosis include gout, arthritis, trauma, certain tumours, a foreign body, and several other possible causes of non-infective Joint Pain

There several possible mechanisms for an infection to develop in a joint: 

  1. Joint sepsis may occur by direct implantation of bacteria into the bone from outside the body, (a process known as 'direct extension').  A good example of this would be a patient stepping on a nail, with the nail transmitting an infection directly into the joint.  

  2. Joint sepsis may also occur by spreading from an already-existing infection spread from an adjacent bone or soft tissue.  This is a process known as contiguous spread.

  3. Another common way of developing osteomyelitis is from spread from elsewhere in the body.  In this case the infection is seeded into the joint from the blood supply.  This is often categorized as a 'Hematogenous' origin, with "hematogenous" being a reference to its having been spread via the blood. 

  4. Osteomyelitis as a result of peripheral vascular disease (poor circulation) is another possible cause of joint sepsis.  It is most commonly seen in diabetics or patients with other forms of vascular compromise. 

The most common organism involved with joint sepsis in all age groups is Staphylococcus Aureus, but some organisms tend to prefer certain population groups.  For example, neonates seem to develop Streptococcus infections; children 6 months to 5 years have a higher occurrence of Hemophilus Influenza; teens tend to develop Neisseria infections more than other groups; Pseudomonas tends to be common with puncture wounds; Salmonella is common in those with sickle-cell disease; and the patient with diminished immunity (AIDS patients, IV drug users, those taking steroids, those undergoing chemotherapy) have a higher incidence of Serratia.

Laboratory blood work (ESR, CRP, WBC, blood cultures, e.g.) can be helpful in diagnosing joint sepsis, as can imaging techniques like traditional bone scans and seratec scans, as well as MRI and CT, but one of the most accurate and quickest methods is joint aspiration, (also known as arthrocentesis), where joint fluid is analyzed after being withdrawn from the joint by a needle.  In the presence of an infection, the fluid tends to become cloudy and has a much higher-than-normal number of white blood cells.  

Another method to help diagnose joint sepsis and assess its extent is also a treatment--surgical intervention to open up, drain and test a joint for infection may be the best way to visualize the damage to a joint caused by joint sepsis.  Though critics of this technique correctly point out that the surgery, itself, may cause scar tissue and joint damage, sometimes there is no other option.  Surgery may often be required to fully resolve the joint infection, and delaying such surgery can result in the complete destruction of the joint from sepsis.  Such surgery is usually combined with PMMA beads, IV and/or oral antibiotics. 




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The Achilles Foot Health Centre
S. A. Schumacher, D.P.M., F.A.C.F.A.S., F.A.C.F.A.O.M.  
Dr. S. A. Schumacher, Podiatric Corporation  

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