What is pseudoseptic arthritis?
Pseudoseptic arthritis is a very rare and unpredictable complication that can occur following a hyaluronic acid (HA) injection (Pullman-Mooar and Mooar, 2005 Sedrak et al., 2021; Ong et al., 2021).
Pseudoseptic arthritis presents like a joint infection (sepsis) but without infection (Aydin et al., 2016; Ong et al., 2021).
We currently do not understand what causes pseudoseptic arthritis. However, a variety of theories have been presented within the research. These include:
- An inaccurate injection. If the HA is accidentally deposited outside the joint, it is thought that the synovial fluid (the fluid within a joint) drainage tracts can become blocked, leading to the development of pseudoseptic arthritis (Sedrak et al., 2021).
- Joint hypersensitivity. The introduction of HA into a joint initiates a proinflammatory effect which causes the joint to become hypersensitive to HA. It is believed that once a joint becomes hypersensitive to HA, when it encounters this stimulus again (such as a second or third injection), a potent inflammatory cascade occurs resulting in a significantly painful reaction known as pseudoseptic arthritis (Sedrak et al., 2021; Pullman-Mooar and Mooar, 2005; Aydin et al., 2016).
What are the symptoms of pseudoseptic arthritis?
Pseudoseptic arthritis following HA injection is difficult to differentiate from septic arthritis. However, a clue can be found in the time of symptom onset. Sepsis typically takes at least five days to develop. This is in contrast with pseudoseptic arthritis which presents within the first 48 to 72 hours (Sedrak et al., 2021; Ong et al., 2021). Patients suffering from pseudoseptic arthritis present with a sudden onset of acute pain and swelling in the recently injected joint. There is also an associated loss of function. In rare cases patients may also present with fever (Ong et al., 2021).
If symptoms develop with 48-72 hours after an injection of HA, pseudoseptic arthritis must be considered.
Patients can become sensitised to HA over time and the risk of developing pseudoseptic arthritis becomes greater the more HA injections a person has, although this is not always the case. Less commonly, pseudoseptic arthritis can occur after a single HA injection (Sedrak et al., 2021).
Are there any risk factors associated with pseudoseptic arthritis?
There are a number of risk factors associated with the development of pseudoseptic arthritis. These are:
- Patients under the age of 40 have an increased risk of developing pseudoseptic arthritis when compared to older patients.
- High molecular weight HA has been associated with increased risk of pseudoseptic arthritis when compared to lower molecular weight HA.
- Previous HA injection increases the risk of developing pseudoseptic arthritis 8-fold.
- Patients who undertook an arthroscopy in the week preceding an HA injection have a 299% increase in risk of developing pseudoseptic arthritis.
- Patients who received a corticosteroid injection in the week preceding an HA injection have been reported to have a 90% increase in risk of developing pseudoseptic arthritis.
- Research has shown Synvisc (a brand of HA) to be associated with the highest rate of developing pseudoseptic arthritis whereas Ostenil (another brand of HA) appears to be much safer with only one recorded case of pseudoseptic arthritis (Aydin et al., 2016).
Interestingly, combining HA with a corticosteroid lowers the risk of developing pseudoseptic arthritis by 87% (Ong et al., 2021).
How is pseudoseptic arthritis diagnosed?
Diagnosing pseudoseptic arthritis is challenging as it can present just like septic arthritis (Aydin et al., 2016).
As previously discussed, the vast majority of pseudoseptic arthritis cases develop within the first 72 hours after HA injection. This is in contrast to sepsis which takes longer to develop, typically developing over 5 to 7 days after injection. It is incredibly rare for sepsis to develop in the first 72 hours post HA injection (Ong et al., 2021; Aydin et al., 2016).
Joint sepsis a is an incredibly serious condition which can result in disastrous outcomes (loss of limb or life) if not treated. Therefore, it is vitally important that sepsis be ruled out, or treated, as soon as possible. Sepsis after a HA injection is incredibly rare with a reported incidence rate of 7 cases per 100,000.
A diagnosis of septic arthritis is made with:
Plane X-ray.
Blood tests which reveal –
- Elevated leucocyte counts. This assesses the amount of white blood cells there are in the blood. White blood cells are created in the bone marrow and are vitally important for fighting infection. A normal white blood cell count of between 4,500 to 11,000 per microlitre indicates a healthy immune system. A high white cell count can indicate infection/sepsis.
- Elevated C reactive protein (CRP). CRPs are developed in the liver and released in response to infection/sepsis. A normal CRP count is less than 10mg/L, with an increase in CRP level indicating infection/sepsis.
- Elevated erythrocyte sedimentation rate (ESR). The time it takes red blood cells to settle in a test tube is known as the sedimentation rate. Normal sedimentation rates vary between sexes – males are 0-22mm/hr; women are 0-29mm/hr). An elevated sedimentation rate may be a sign of infection/sepsis.
Joint aspiration (arthrocentesis)-
- Elevated synovial leucocyte counts (Pullman-Mooar and Mooar, 2005). Elevated white blood cell counts in the synovial fluid (joint fluid) can indicate joint infection. Normal synovial leucocyte counts are < 200 x 106/L.
Generally, a diagnosis of pseudoseptic arthritis is made in the absence of any sign of infection/sepsis (Sedrak et al., 2021). However, this is not always the case. Occasionally patients suffering from pseudoseptic arthritis have blood tests which reveal elevated levels of the aforementioned inflammatory markers but the joint aspirate results are normal (Aydin et al., 2016). In these cases, a surgical wash out and a course of antibiotics is required.
How is pseudoseptic arthritis treated?
The majority of patients suffering from pseudoseptic arthritis notice an improvement in symptoms without the need for antibiotics or surgical intervention. However, in severe cases surgery is required to wash the joint out, removing any irritating material which may be present within the joint.
Pseudoseptic arthritis is treated with:
- Non-steroidal anti-inflammatory medication. 46.4% of patients require a course of oral anti-inflammatory medications.
- Steroid injection. 57.1% of patients require a steroid injection directed to the affected joint.
- Surgery. Surgical wash out of the affected joint has been reported in 7.1% of cases.
- Antibiotics. In some cases, a course of prophylactic antibiotics is required.
(Pullman-Mooar and Mooar, 2005; Sedrak et al., 2021; Ong et al., 2021)
How long does pseudoseptic arthritis take to resolve?
In general, significant improvements have been reported to occur within an average of 3 weeks post treatment (Sedrak et al., 2021). Suffering from an episode of pseudoseptic arthritis has been reported to have no long-term damaging effects (Pullman-Mooar and Mooar, 2005).
If you believe you are suffering from either pseudoseptic arthritis or sepsis it is vitally important that you seek immediate medical assistance. Go to your local A&E department immediately and alert your treating clinician at Complete.
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