Paeds · investigations-procedures-and-technology
Joint aspiration
Also known as Arthrocentesis · Synovial fluid aspiration · Joint tap · Paediatric joint aspiration · Hip aspiration · Synovial fluid analysis
Fellowship guide to joint aspiration (arthrocentesis) in infants and children. Covers the indications, the single biggest question of septic arthritis versus transient synovitis, the Kocher and Caird predictors (fever above 38.5°C, refusal to bear weight, ESR above 40, white cell count above 12,000 and CRP above 20), the relative contraindications of overlying cellulitis and uncorrected coagulopathy, why the deep paediatric hip is aspirated under ultrasound guidance, the synovial fluid cell-count categories that separate septic from inflammatory from non-inflammatory effusions, the sterile technique and landmarks for the knee, hip, ankle and shoulder, the local anaesthetic infiltration and its safe dose, and the common and serious complications including infection seeding and bleeding.
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Target exams
Red flags
- A febrile child with a hot, swollen, painful joint who refuses to bear weight and has a raised inflammatory response — this is septic arthritis until proven otherwise, a time-critical orthopaedic emergency in which delayed aspiration and drainage destroy articular cartilage within hours
- Passing the aspiration needle through overlying cellulitis — the needle seeds skin flora into the sterile joint space and converts a soft-tissue infection into iatrogenic septic arthritis
- Aspirating a child with uncorrected coagulopathy or thrombocytopenia, or a boy with haemophilia who has not had factor cover — the procedure produces a tense haemarthrosis and can compromise the neurovascular status of the limb
- Aspirating a deep joint, especially the hip, blind — in a child the hip is deep, the landmarks are hard to feel, and an unguided needle misses the effusion, injures cartilage or strikes the femoral neurovascular bundle
- Accepting a normal or low synovial white cell count as proof that septic arthritis is excluded — partially treated and Kingella kingae septic arthritis frequently present with cell counts below 50,000 per microlitre, so the result is read with the whole clinical picture, not in isolation
- Treating a hot swollen joint with antibiotics before the synovial fluid is sent — without a Gram stain, cell count and culture the organism is guessed at, the child is committed to broad cover, and the chance of a positive culture falls after the first antibiotic dose
Life stages
Care settings
Clinical exam formats
Board mappings
- Procedures and investigations
- Perform and supervise a joint aspiration in an infant or child
- Recognition of the limping child with a possible septic joint
- Current 2026 PREP curriculum — Learning goal 11: Investigations and procedures
- Renewed curriculum for first-year trainees from 2027 — Learning goal 11: Investigations and procedures
- Safe performance and supervision of paediatric arthrocentesis under ultrasound guidance
- Written Examination
- Clinical Applications
- Musculoskeletal and infectious-disease emergencies requiring arthrocentesis
- Short Cases
- Procedural skills and consent
- Communication and patient-safety scenarios
- 11. Investigating and managing paediatric presentations
- Level 2: Performs common paediatric procedures including joint aspiration with appropriate supervision
- Patient safety: recognising septic arthritis and the relative contraindications to aspiration
- Applied Knowledge in Practice (AKP)
- Foundations of Practice (FOP)
- Procedures: indications, contraindications, technique and complications of arthrocentesis
- Clinical
- Communication scenarios
- Safe procedural skills and consent
- General Pediatrics Content Outline — Procedural skills: arthrocentesis
- General Pediatrics Content Outline — Musculoskeletal and infectious diseases
- General Pediatrics EPA: Perform a joint aspiration in an infant or child
- Patient Care 3: Procedural skills
- Medical Knowledge 1: Clinical knowledge
- Systems-Based Practice: safe procedural practice and consent
- Medical Expert
- Communicator
- Pediatrics: Core EPA — Perform a joint aspiration in an infant or child
Overview & Definition
Picture the three-year-old who will not walk, carried into the emergency department with a flexed hip and a face that says pain, or the eight-year-old with a knee swollen tight and hot after a fever. In both, question team must answer quickly is whether there is infection in the joint, because septic arthritis dissolves articular cartilage within hours and the only way to answer the question with certainty is to aspirate the synovial fluid and analyse it. That is the territory this page owns. [5] [10]
A joint aspiration (arthrocentesis) is the percutaneous passage of a hollow needle through skin, subcutaneous tissue and the joint capsule into the synovial cavity, to withdraw synovial fluid for diagnostic analysis, to decompress a tense effusion or haemarthrosis, or to instil a drug such as a corticosteroid. The core diagnostic use is the child with a possible septic joint, where the cell count, Gram stain and culture of the fluid settle the diagnosis that no blood test or imaging can settle alone. The therapeutic uses are drainage of a painful effusion, washout of a septic joint in concert with the orthopaedic team, and the intra-articular corticosteroid injection that is a mainstay of juvenile idiopathic arthritis care. [12] [11]
What makes paediatric arthrocentesis a distinct skill from the adult procedure is the child who cannot hold still, the joints that are small and superficial or deep and inaccessible, and the clinical decision that dominates everything else — separating septic arthritis from the common and benign transient synovitis of the hip. The fellowship skill being tested is reading the limping child, applying the prediction rules to decide who crosses the threshold to aspiration, choosing the right joint and the right guidance, and performing a calm single-pass sterile procedure that yields diagnostic fluid without harm. [1] [10]
References12ShowHide
- [1]Kocher MS, Zurakowski D, Kasser JR Differentiating between septic arthritis and transient synovitis of the hip in children: an evidence-based clinical prediction algorithm J Bone Joint Surg Am, 1999.PMID 10608376
- [2]Kocher MS, Mandiga R, Zurakowski D, et al Validation of a clinical prediction rule for the differentiation between septic arthritis and transient synovitis of the hip in children J Bone Joint Surg Am, 2004.PMID 15292409
- [3]Luhmann SJ, Jones A, Schootman M, et al Differentiation between septic arthritis and transient synovitis of the hip in children with clinical prediction algorithms J Bone Joint Surg Am, 2004.PMID 15118038
- [4]Valisena S, De Marco G, Vazquez O, et al The Kocher-Caird Criteria for Pediatric Septic Arthritis of the Hip: Time for a Change in the Kingella Era? Microorganisms, 2024.PMID 38543601
- [5]Nannini A, Giorgino R, Bianco Prevot L, et al Septic arthritis in the pediatric hip joint: a systematic review of diagnosis, management, and outcomes Front Pediatr, 2023.PMID 38188916
- [6]Olandres RA, Seng DWR, Seneviratna A, et al C-reactive protein of at least 20 mg per litre and ultrasound finding of an effusion of at least 7 mm has a high specificity and sensitivity in diagnosing paediatric hip septic arthritis Arch Orthop Trauma Surg, 2023.PMID 37530844
- [7]Cavalier R, Herman MJ, Pizzutillo PD, et al. Ultrasound-guided aspiration of the hip in children: a new technique Clin Orthop Relat Res, 2003.PMID 14612652
- [8]Michaud J, Dutron S, Pico J, et al The feasibility and safety of ultrasound-guided puncture for treatment of septic arthritis in children Ital J Pediatr, 2024.PMID 39334397
- [9]Nouri A, Walmsley D, Pruszczynski B, et al Transient synovitis of the hip: a comprehensive review J Pediatr Orthop B, 2014.PMID 23812087
- [10]Naranje S, Kelly DM, Sawyer JR A Systematic Approach to the Evaluation of a Limping Child Am Fam Physician, 2015.PMID 26554284
- [11]Li S, Zhang W, Lin Y Application of Intra-articular Corticosteroid Injection in Juvenile Idiopathic Arthritis Front Pediatr, 2022.PMID 35425732
- [12]Tantillo TJ, Boudreaux S, Katsigiorgis G Arthrocentesis StatPearls, 2026.PMID 32491737