What is Periprosthetic Joint Infection?
Periprosthetic joint infection (PJI) is an infection involving a joint replacement implant and the tissue immediately surrounding it. It is one of the most feared complications of hip and knee replacement surgery — not because it is common, but because of the severity of its consequences and the complexity of its treatment.
Unlike a simple wound infection that can be treated with antibiotics, PJI involves bacteria adhering to the surface of the implant and forming a biofilm — a structured community of microorganisms enclosed in a protective matrix. Biofilm renders bacteria dramatically more resistant to antibiotics than their free-floating counterparts, and is the reason why PJI almost always requires surgical intervention to achieve cure. The implant itself becomes a foreign body that harbours the infection and protects it from both the immune system and antibiotic treatment.
PJI may occur at any time after joint replacement surgery — from the immediate post-operative period through to many years later. The timing, the causative organism, and the condition of the surrounding bone and soft tissue all influence the treatment strategy and the likelihood of a successful outcome.
Mr. Lodge has a specialist interest in PJI gained through advanced fellowship training at the Royal Orthopaedic Hospital Birmingham — a national referral centre for complex infection and reconstruction surgery — and manages PJI cases within a multidisciplinary team (MDT) that includes specialist orthopaedic microbiologists, infectious disease physicians and radiologists.
A note on where PJI surgery is performed: The surgical management of periprosthetic joint infection is complex, resource-intensive and almost always requires facilities and specialist support that are not available in the private hospital setting. PJI surgery at York is performed exclusively at York Teaching Hospital NHS Foundation Trust, where Mr. Lodge has access to specialist orthopaedic microbiologists, infectious disease physicians, a dedicated MDT infection meeting, inpatient intravenous antibiotic delivery and monitoring, and the full range of diagnostic and laboratory services that safe PJI management requires. Private hospitals in York do not have the infrastructure to safely support this care pathway. Mr. Lodge is happy to see patients in the private setting for assessment, investigation coordination and advice — but surgical treatment of confirmed PJI will be arranged and performed within the NHS at York Teaching Hospital.
PJI is a medical and surgical emergency in its acute form. A patient with acute fever, wound breakdown and rapidly worsening joint pain after recent joint replacement surgery should seek urgent medical review. If you are concerned about a recently operated joint, contact the hospital where your surgery was performed directly or attend your nearest Emergency Department.
How Does PJI Present?
PJI does not always look the same. The way it presents depends critically on when it occurs after surgery and which organism is responsible. Recognising the different presentations is essential — both for the patient, who needs to know what to look out for, and for the clinician, who must tailor the diagnostic approach accordingly.
Acute PJI
Within 4–6 weeks of surgery, or sudden onset in a previously well joint
- Rapid onset of severe pain in the operated joint, often disproportionate to the expected post-operative course
- Wound breakdown, persistent wound discharge or failure to heal
- Redness, warmth and marked swelling of the joint and surrounding tissues
- Systemic features — fever, sweats, rigors, feeling generally unwell
- In haematogenous (blood-borne) cases — a previously well-functioning replacement that suddenly becomes acutely painful, often in the context of an infection elsewhere in the body (dental, urinary, skin)
- Typically caused by virulent organisms: Staphylococcus aureus (including MRSA), Streptococcus, Gram-negative bacteria
Chronic / Indolent PJI
Months to years after surgery — often subtle and easily missed
- Persistent low-grade pain that has never fully resolved since surgery — or pain that improved then gradually returned
- Stiffness and restricted range of movement without clear mechanical explanation
- Recurrent or persistent joint effusion (swelling)
- A discharging sinus tract — a persistent wound that never fully closed after surgery, even months or years later
- Implant loosening on X-ray at an unusually early stage after surgery
- Typically caused by low-virulence organisms: coagulase-negative Staphylococci (e.g. Staphylococcus epidermidis), Propionibacterium acnes — which can be extremely difficult to culture and require prolonged microbiological incubation
The indolent presentation is the most dangerous from a diagnostic perspective. A patient with chronic, low-grade PJI caused by a slow-growing organism may have normal or only mildly elevated inflammatory markers, no obvious signs of infection, and X-rays that are initially interpreted as showing aseptic loosening. A high index of suspicion and a systematic investigation protocol are essential to avoid missing this diagnosis — and treating a joint as mechanically loose when it is in fact infected will result in early failure of any revision surgery.
Investigating for PJI
There is no single test that diagnoses PJI with complete certainty. Diagnosis requires a combination of clinical assessment, blood tests, imaging and — critically — joint aspiration with microbiological culture. The more tests that point towards infection, the more confident the diagnosis; the more that are negative, the more confident the exclusion.
International diagnostic criteria — developed by the Musculoskeletal Infection Society (MSIS), the International Consensus Meeting (ICM 2018) and the European Bone and Joint Infection Society (EBJIS 2021) — provide structured frameworks for combining these tests into a diagnostic classification. Mr. Lodge applies current EBJIS criteria in clinical practice, as these represent the most contemporary evidence-based approach.
Blood Tests
First-line screening
- CRP (C-reactive protein) — the most useful single blood marker. Elevated in acute PJI; may be normal or only mildly raised in chronic infection
- ESR (erythrocyte sedimentation rate) — less specific than CRP but useful in combination. Remains elevated for longer after surgery and after acute infection
- White cell count — may be elevated in acute PJI; often normal in chronic or low-grade infection
- D-dimer and fibrinogen — increasingly recognised as useful adjuncts to CRP and ESR in PJI diagnosis, particularly in the context of normal or borderline CRP
- Serum interleukin-6 (IL-6) — a highly sensitive early marker of infection, useful in the immediate post-operative period when CRP is non-specifically elevated
Joint Aspiration
The most informative single investigation
- Performed under image guidance (fluoroscopy or ultrasound) to ensure the needle enters the joint rather than the surrounding soft tissue
- Synovial fluid white cell count and differential — an elevated count with a predominance of polymorphonuclear (PMN) cells strongly suggests infection. Thresholds differ for acute versus chronic PJI
- Microbiological culture — samples are held for a minimum of 14 days to allow slow-growing organisms such as Propionibacterium acnes and coagulase-negative Staphylococci to be detected
- Alpha-defensin assay — a synovial fluid biomarker with high sensitivity and specificity for PJI. Particularly valuable where standard tests are equivocal, and where antibiotics have been given prior to aspiration (which can suppress culture results)
- Leukocyte esterase strip test — a rapid, low-cost bedside test of synovial fluid that provides a near-immediate indication of inflammatory cell content
Imaging
Supporting evidence and planning
- Plain X-rays — may show periosteal reaction, progressive radiolucent lines at the implant-bone interface, or early loosening at an unexpected stage. Normal X-rays do not exclude PJI
- CT scan — assesses the extent of bone loss and component position, but limited for soft tissue assessment around metal implants
- MARS MRI (metal artefact reduction sequences) — particularly valuable in suspected ARMD (adverse reaction to metal debris) but also useful for assessing peri-implant soft tissue changes and sinus tract anatomy in PJI
- Nuclear medicine / SPECT-CT — white cell-labelled scintigraphy can identify areas of active infection around an implant; useful where aspiration is equivocal or technically difficult
Intraoperative Confirmation
At time of revision surgery
- Intraoperative tissue biopsies — multiple samples taken from the membrane around the implant and sent for both histology (looking for acute inflammatory cells) and prolonged microbiological culture
Antibiotics before aspiration. If PJI is suspected, antibiotics should ideally be withheld until after joint aspiration has been performed and microbiological samples obtained. Starting antibiotics before culture dramatically reduces the chance of identifying the causative organism — which in turn makes targeted antibiotic therapy impossible and significantly compromises the outcome of treatment.
How is PJI Treated?
The treatment of PJI is always surgical, always multidisciplinary, and always tailored to the individual patient — based on the timing of infection, the causative organism, the condition of the bone and soft tissue, and the patient's overall health and fitness for surgery.
Antibiotics alone are not curative for established PJI. The biofilm that bacteria form on the implant surface renders them many times more resistant to antibiotics than their free-floating counterparts — concentrations that would be required to sterilise biofilm in vivo are not achievable without toxicity. Surgical debridement and, in most cases, removal of at least part or all of the implant are necessary to achieve cure.
Surgical Treatment Options
DAIR — Debridement, Antibiotics & Implant Retention
In carefully selected patients with acute PJI (within 4–6 weeks of surgery, or acute haematogenous infection in a well-fixed implant) and a sensitive organism, the implant may be retained. The joint is opened, thoroughly washed out, all infected and necrotic tissue is debrided, and exchangeable components (such as the polyethylene liner) are changed. This is followed by a prolonged course of targeted antibiotics including biofilm-active agents. DAIR is appropriate only in acute presentations with a well-fixed implant and a susceptible organism — patient selection is critical.
Acute PJI — selected casesTwo-Stage Revision Exchange
The gold standard for chronic PJI in the UK. All implants and cement are removed in a first-stage operation, the joint is thoroughly debrided, and an antibiotic-loaded cement spacer is inserted to maintain joint space and deliver high local antibiotic concentrations. A targeted antibiotic course guided by the identified organism follows. Once infection eradication is confirmed — through clinical review, normalisation of inflammatory markers and, where appropriate, repeat aspiration — a second-stage reimplantation is performed using definitive revision implants. The interval between stages is typically 6–12 weeks depending on the organism and the pace of recovery.
Standard for chronic PJIOne-Stage Revision Exchange
In selected patients — where the organism is known and sensitive to antibiotics, the soft tissues are in good condition, and the patient is medically fit — exchange of all components at a single sitting (after thorough debridement) may be considered. This avoids the period with a spacer and reduces the total surgical burden. The evidence base for single-stage exchange is growing, particularly for hip PJI. Mr. Lodge discusses the relative merits of one- versus two-stage revision with each patient individually, guided by the microbiology, clinical factors and current evidence.
Selected cases — growing evidenceExcision Arthroplasty / Long-term Suppression
In patients who are not fit for revision surgery — due to significant comorbidity, frailty or repeated failure of eradication — permanent removal of the implant without reimplantation (excision arthroplasty) may occasionally be the safest option. In others where surgery carries prohibitive risk, long-term suppressive antibiotics may be used to control symptoms, accepting that infection will not be eradicated. These are last-resort options discussed openly and honestly with patients and their families.
Salvage — high-risk or unfit patientsThe Role of the Multidisciplinary Team
PJI is never managed by the orthopaedic surgeon alone. Optimal outcomes require close collaboration with specialist orthopaedic microbiologists — who guide antibiotic choice, duration and monitoring — and where appropriate, infectious disease physicians, radiologists and plastic surgeons. Mr. Lodge manages all PJI cases within a structured MDT framework at York Teaching Hospital NHS Foundation Trust, ensuring that every decision about antibiotic therapy, surgical timing and reimplantation is made collectively and with access to the full depth of specialist expertise.
This multidisciplinary approach also requires infrastructure that is not available in the private hospital setting — including inpatient intravenous antibiotic delivery, specialist microbiology laboratory services, community antibiotic outreach teams, and a dedicated infection MDT meeting. For these reasons, the surgical treatment of PJI is performed exclusively within the NHS at York Teaching Hospital. Mr. Lodge is pleased to see patients privately for initial assessment, investigation and advice, but surgical management will always be arranged through the NHS pathway.
This multidisciplinary model mirrors that of the Royal Orthopaedic Hospital Birmingham, where Mr. Lodge undertook his specialist fellowship training in PJI management.
The Role of Antibiotics in PJI
Antibiotics are an essential but insufficient treatment for PJI on their own. Their role is to complement surgical debridement — reducing the bacterial burden, preventing spread and suppressing residual organisms — not to replace surgery.
Targeted Therapy
The choice of antibiotic is guided entirely by the identity and sensitivity profile of the causative organism identified from cultures taken at aspiration or at the time of surgery. This is why organism identification is so important — broad-spectrum empirical antibiotics without a known target organism are far less effective and carry greater risks of side effects and resistance development.
For biofilm-associated organisms — particularly Staphylococci — rifampicin is an important adjunct antibiotic. Rifampicin has specific activity against bacteria within biofilm and is typically combined with another agent to prevent rapid resistance development. Its use is guided by the microbiologist and requires careful monitoring.
Duration and Route
The duration and route of antibiotic therapy varies considerably depending on the clinical scenario. In the two-stage exchange pathway, an initial period of intravenous antibiotics following the first-stage debridement is typically followed by a prolonged course of oral antibiotics before reimplantation is considered. Total antibiotic duration is usually three to six months, though this varies with organism and clinical response. The decision to proceed to second-stage reimplantation is never based solely on a fixed time interval — clinical and laboratory evidence of infection eradication must be clearly established first.
- DAIR: Typically 3–6 months of antibiotics following debridement, including biofilm-active agents such as rifampicin for Staphylococcal infections
- Two-stage revision: IV antibiotics post first-stage, followed by oral therapy; total duration typically 3–6 months before reimplantation is considered
- One-stage revision: Prolonged oral antibiotics post-operatively, guided by the microbiologist
- Suppressive therapy: Long-term low-dose oral antibiotics in patients not suitable for surgery; aimed at symptom control rather than cure
Preventing PJI
Given the severity and complexity of treatment, prevention of PJI is far preferable to treating it. A number of evidence-based measures are employed at every joint replacement performed by Mr. Lodge to minimise infection risk as far as possible.
- Pre-operative MRSA screening and decolonisation: All patients are screened for MRSA carriage at pre-assessment and given decolonisation treatment if positive, using chlorhexidine body wash and nasal mupirocin ointment
- Prophylactic antibiotics: A carefully timed dose of intravenous antibiotic is given at induction of anaesthesia, timed to achieve maximum tissue concentration at the time of incision. The choice of antibiotic accounts for any known MRSA carriage or penicillin allergy
- Laminar flow operating theatre: All arthroplasty surgery is performed in laminar flow theatres, which provide ultra-clean air filtration to reduce airborne bacterial contamination of the wound
- Surgical technique: Meticulous handling of soft tissues, minimising operative time, thorough irrigation and careful wound closure all reduce infection risk
- Optimising patient health before surgery: Treating active infections elsewhere in the body, optimising diabetic control, encouraging smoking cessation and weight loss, and reviewing immunosuppressive medications before surgery all reduce the risk of post-operative infection
- Dental health: Active dental infection must be treated before joint replacement surgery. Patients are advised on the importance of prompt dental care throughout the lifetime of their replacement — see the Your Operation page for detailed guidance
Lifelong vigilance: The risk of haematogenous PJI — where bacteria seed the replacement from a distant infection via the bloodstream — persists throughout the lifetime of the implant. Patients should seek prompt treatment for any infection anywhere in the body, inform treating clinicians that they have a joint replacement, and maintain good general dental hygiene. The implant is never completely immune to infection, and early recognition and treatment of any distant infection remains important indefinitely.
Concerned About Your Joint Replacement?
If you are worried that your joint replacement may be infected — whether recently operated or many years ago — please do not delay in seeking advice. Early diagnosis and treatment significantly improve the chances of a successful outcome.
Mr. Lodge sees patients from across the Yorkshire region and beyond with suspected or confirmed PJI, including referrals from other centres. Initial assessment and investigation can be arranged privately — allowing timely specialist review, coordination of aspiration, blood tests and imaging, and a clear diagnostic and management plan. Where surgical treatment is required, this will be arranged through the NHS at York Teaching Hospital, where the full infrastructure for safe PJI management is available.
If you are a clinician wishing to refer a patient for specialist PJI assessment, please contact the secretary. NHS referrals can also be directed to Mr. Lodge via the standard referral pathway at York Teaching Hospital.
If your symptoms are acute and severe — rapidly worsening pain, fever, wound breakdown — please contact the hospital where your surgery was performed directly or attend the Emergency Department. Do not wait for an elective appointment.