What is pseudoseptic arthritis?
Pseudoseptic arthritis is a very rare complication following corticosteroid (CS) injection which mimics septic arthritis (Peterson et al., 2011; Aydin et al., 2016; Paul et al., 2021; Prodip et al., 2021). Whilst still an incredibly rare complication, pseudoseptic arthritis is more likely to occur after injecting hyaluronic acid than CS.
Pseudoseptic arthritis has been defined as an inflammatory arthritic condition in the absence of bacterial infection (Oppermann et al., 2011).
Risk factors associated with developing pseudoseptic arthritis
There are a number of risk factors involved in the development of pseudoseptic arthritis following a CS injection. These are:
- Previous hyaluronic acid injections in the same joint.
- Multiple previous injections in the same joint.
- Behcet’s disease (a rare condition resulting in the inflammation of the blood vessels).
- Systemic rheumatological conditions such as rheumatoid arthritis, psoriatic arthritis, reactive arthritis, lupus, gout and ankylosing spondylitis.
- TNF-alpha blocker medication (a group of biological medications used to treat rheumatological conditions)
What are the symptoms associated with pseudoseptic arthritis?
Symptoms of pseudoseptic arthritis can be very difficult, if not impossible, to differentiate from septic arthritis following a CS injection (Oppermann et al., 2011) and therefore immediate medical assistance is required to confirm the presence of either pathology.
Below is a table comparing the most common signs and symptoms of both pseudoseptic arthritis and septic arthritis.
| Pseudoseptic arthritis symptoms | Septic arthritis symptoms |
|---|---|
| A significant increase in pain, often this develops within the first 72 hours | A significant increase in pain, often this takes 5 days to start developing. This is different from a post injection pain flare which develops within 24-48 hours after injection. |
| Joint swelling is rare but can be present in some cases | Joint swelling |
| No redness or heat in the joint | A red, hot, angry joint |
| Fever is rare but can occur | Fever |
| Significant loss of joint function secondary to pain | Significant loss of joint function |
| Generally inflammatory markers (via blood tests) are not elevated, although not always the case | Increased inflammatory markers (via blood tests) |
As you can see there are subtle differences in the presentation of these two conditions. Clinical assessment alone is not enough to safely differentiate pseudoseptic arthritis from septic arthritis, so it is vitally important to seek medical help as soon as possible for a definitive diagnosis.
How is a diagnosis of pseudoseptic arthritis made?
Septic arthritis is a very rare (1:50,000) but serious complication following CS injection which, if not treated quickly, can result in devastating consequences (Peterson et al., 2011). It is therefore essential that septic arthritis is ruled out or treated as soon as possible.
If you experience any of the above signs and symptoms, it is essential that you go to A&E immediately.
As previously mentioned, both pseudoseptic arthritis and septic arthritis present very similarly which makes it impossible to differentiate between these two rare conditions without running a series of medical tests (Oppermann et al., 2011). A diagnosis of pseudoseptic arthritis can only be safely made after septic arthritis has been ruled out (Aydin et al., 2016; Paul et al., 2021).
A definitive diagnosis of either septic arthritis or pseudoseptic arthritis is made via a combination of the following tests:
X-ray
An X-ray can reveal the presence of joint effusion as well as pathological changes to both the cartilage and underlaying subchondral bone surfaces.
Blood tests
Normal blood test results point to a diagnosis of pseudoseptic arthritis; abnormal results point to septic arthritis
Blood test results confirming infection reveal –
- Elevated white blood cell (leucocyte) levels. White blood cells are part of a healthy immune system and vital for fighting infection. If leucocyte levels are higher than expected (normal white blood cell counts range between 4,500 and 11,000/microlitres) then infection is indicated.
- Elevated C reactive protein (CRP). CPR cells are produced by the liver and are released to combat infection. Normal CRP levels are no more than 10mg/L. Elevated CRP levels indicate possible infection.
- Elevated erythrocyte sedimentation rate (ESR). ESR refers to how long it takes for red blood cells to settle at the bottom of a test tube. Normal ESR rates in men are 0-22mm/hr. In women normal ESR rates are 0-29mm/hr. When ESR is increased an infection is suspected.
Elevated synovial fluid leucocyte levels
A joint suspected to be harbouring infection is often swollen, red and hot. If this is the case a joint aspiration is required. A needle is introduced into the joint and a small amount of fluid is withdrawn. Infected joint fluid often appears cloudy and may contain pus. The fluid sample is then assessed for elevated synovial (joint fluid) leucocyte levels. Normal levels are are < 200 x 106/L. When elevated leucocyte levels are detected, infection is suspected.
A formal diagnosis of pseudoseptic arthritis is made when septic arthritis has been ruled out (Oppermann et al., 2011).
How is pseudoseptic arthritis treated?
Pseudoseptic arthritis is not self-limiting (meaning it will not resolve without treatment). In other words, treatment is essential to recover from an episode of pseudoseptic arthritis (Oppermann et al., 2011).
Treating pseudoseptic arthritis requires either a course of non-steroidal anti-inflammatory medication or a further intra-articular (joint) CS injection. However, with severely ill patients and when the joint fluid appears purulent (on aspiration) then a course of antibiotics is immediately prescribed, and a sample is sent away for microbiological testing. If microbiological testing returns normal (normal synovial fluid leucocyte levels) then antibiotic medication can be stopped (Oppermann et al., 2011; Paul et al., 2021).
How long does it take to recover from pseudoseptic arthritis?
Recovery from a bout of pseudoseptic arthritis is relatively quick. After being treated with a course of non-steroidal anti-inflammatory medication or a further CS injection the majority of patients can be expected to be discharged from hospital within six days (Oppermann et al., 2011) and significant improvements are to be expected within an average of 3 weeks after treatment (Sedrak et al., 2020). Importantly, and reassuringly, no long-term damaging effects have been reported following a bout of pseudoseptic arthritis (Oppermann et al., 2011; Pullman-Mooar et al., 2016).
If you think you may be experiencing either pseudoseptic arthritis or septic arthritis, it is of paramount importance that you seek immediate medical assistance. Attend your local A&E department immediately and alert your treating clinician at Complete.
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