Septic arthritis is bacterial (rarely fungal) infection within a joint or joints. It is important to detect and treat early in order to prevent life-threatening sepsis and chondrolysis (articular cartilage damage) which can occur within hours. It classically presents with an acute/subacute hot, painful, swollen joint with systemic features of infection.
Important determinants of treatment include whether the joint involved is native (i.e. the patient’s own) or prosthetic (i.e. a joint replacement) and whether or not the patient is systemically unwell (pyrexia, sepsis).
Please note that this page is specifically regarding adult septic arthritis. Paediatric septic arthritis, although sharing many similarities, has its own page.
If the patient is unwell, or you have any concerns that they might be, make sure to assess and resuscitate the patient according to an ALS/A-E principle, and consult senior help early if needed.
Which joint(s) is/are affected?
What local symptoms (pain, swelling, loss of movement, inability to weight bear) does the patient have and when did they start?
Has there been any trauma?
Are there any symptoms of systemic illness (fevers, rigors, shakes, sweats, shivers)?
Past medical history / Drug history / Social history
Any previous surgery to that joint?
Diabetes or any other immunosuppression?
All regular medications, but especially:
- Steroids or other immunosuppressants
- Antibiotics within the last two weeks
Ask about IV drug abuse, smoking and alcohol
Look: redness, swelling, position
- A septic knee will classically be held in slight flexion
- A septic hip will classically be slightly flexed, abducted and externally rotated
Feel: temperature, joint line tenderness, effusion
Move: active and passive ROM
Examine other joints including the spine, as well as the joint of interest
XR of the affected joint
- Looking for an effusion
- To check for fracture or tumour
- All patients: FBC, CRP, U&Es
- If suspecting gout: urate
- If unwell/pyrexial: blood cultures, lactate, LFTs
- If anticoagulated: clotting screen
Joint aspirate (see below)
The principles of management of a septic arthritis are to:
- Obtain a sample
- Treat systemic sepsis
- Treat local infection
Ideally, a sample should be obtained before starting antibiotics, but do not delay antibiotics in an unwell patient just to obtain a sample. If you are considering starting antibiotics without a sample, call for senior help first.
Ideally, the joint should be aspirated before starting antibiotics. Most joints (knee, ankle, wrist, shoulder, elbow) can be aspirated using sterile technique in ED or on the ward. Importantly, prosthetic joints must be aspirated in a clean environment (i.e. operating theatre) and hip joints require imaging (ultrasound or fluoroscopy) and are usually also aspirated in theatre. Do not aspirate a joint unless you have been taught in person and are confident to do so, but the principles are:
- Obtain verbal consent
- Thoroughly prepare the skin
- Using sterile, non-touch techniques, aspirate the joint to dryness
- Apply a sterile dressing
- Document: consent, technique, volume of fluid, colour of fluid
- Consider dipstick testing for WCC and glucose (and document results)
- Send urgently to the laboratory, call the technician and ask to be informed of the microscopy results (send for MC&S and crystals)
Again: do not aspirate a prosthetic joint outside of an operating theatre. The risk of introducing periprosthetic infection is too high.
Once a sample has been obtained, commence IV antibiotics as per your trust policy. Consider contacting a microbiologist if there is a previous history of septic arthritis, as this may alter the recommended antibiotics.
Remember the sepsis six, and initiate appropriate fluid resuscitation, urine output monitoring, check lactate and consider involving HDU/ICU if indicated.
- Documented history, examination and observations
- Blood tests (WCC, CRP, U&Es, consider lactate, cultures, urate, LFTs, clotting)
- Aspiration taken if appropriate, sent to lab and technician called
- Senior called if appropriate (see below)
- Empirical antibiotics started if appropriate
- Sepsis management initiated if appropriate
- Patient kept NBM if might require surgery
Admission, discharge and calling a senior
Who to admit:
- Anyone who is systemically unwell
- Anyone who you think might have septic arthritis
When to call a senior:
- Confirmed septic arthritis (organisms seen on aspirate microscopy)
- High suspicion of septic arthritis (e.g. pyrexia and WCC +++ on aspiration, even without organisms)
- You are not able/confident to aspirate the joint (and no-one else can e.g. ED staff)
- Possible prosthetic joint infection with unwell patient (may need aspiration/washout in theatre ASAP)
- Suspected septic native hip (may need aspiration/washout in theatre ASAP)
- You are planning on starting antibiotics without obtaining an aspirate
- A patient with known septic arthritis who is getting worse – repeat washout might be required
Antibiotics are tailored to the organisms grown from initial aspiration. Historically several weeks of IV antibiotics were given, followed by several more weeks of orals, but there is some evidence that early oral switch might be safe in the case of native joints.
Surgical management – native joints
Washout of the joint, either arthroscopically or open, is usually performed as an emergency procedure both to reduce the septic load (to allow treatment of systemic sepsis) and to reduce articular surface damage. This might be indicated overnight, or might be left until the morning, but that decision is not yours to make, so if in doubt call your senior.
Repeat washout might be indicated if a patient deteriorates despite previous washout and antibiotics.
There is some evidence that repeated aspirations (rather than formal washout) might suffice, especially in patients who are high risk for surgery.
Surgical management – prosthetic joints
This is a complex area with significant disagreement amongst surgeons. The aims of management are slightly different, as there is normally no need to preserve articular cartilage (although this may still be a consideration with e.g. unicompartmental knee replacement, or total knee replacement without patellar resurfacing). Clearance of the infection is complicated by the biofilm that develops on prosthetic material, which antibiotics struggle to penetrate.
Emergency washout is rarely performed, unless the patient is sytemically unwell and this is required to reduce the septic load.
Debridement, Antibiotics and Implant Retention (DAIR) is much more than a washout. It involves radical debridement and replacement of any modular components (e.g. the femoral head and acetabular liner of a hip). It is an option mainly in acute/subacute infection (within about three months of onset of infection), before a biofilm has developed.
Single stage revision involves the removal of all prosthetic material, thorough debridement and washout, and re-implantation of a new prosthesis, all in the same operation. Two-stage revision involves an initial operation to remove the infected prosthetic material, debride and washout the joint. The patient is then left either with no prosthesis or with a ‘spacer’ made out of antibiotic-loaded cement for several weeks/months, whilst they receive antibiotic treatment. Once the infection has been cleared, a second operation is carried out to re-implant a new prosthesis.
Patients with limited mobility or a failed revision may be treated with excision arthroplasty (removing the prosthesis and not re-implanting another one). In the hip this may be referred to as a Girdlestone’s operation.
Amputation is always a possibility, especially if other surgical strategies have failed, but it would be very rare for this to be carried out as an urgent case.
Not all patients undergo surgical procedures. Especially if not fit for surgery, or following failed surgical clearance of infection, some patients are instead put on long term antibiotic suppression.
Author: Hamish Macdonald
Last updated: 29/03/2020