INTRODUCTION — Joint aspiration (arthrocentesis) and glucocorticoid injections are used for diagnostic and therapeutic purposes in the care of children with arthritis.
The indications, techniques, and complications of intraarticular aspiration and injection in children are reviewed here. Details regarding ultrasound guidance, the medications used, and the benefits of this procedure for specific conditions are discussed separately. (See "Musculoskeletal ultrasonography: Guided injection and aspiration of joints and related structures" and "Oligoarticular juvenile idiopathic arthritis", section on 'Initial therapy' and "Polyarticular juvenile idiopathic arthritis: Treatment", section on 'Intraarticular glucocorticoids'.)
INDICATIONS — Joint aspiration is primarily performed for diagnostic purposes, usually to rule out infection in a swollen joint. Aspirating fluid can also be therapeutic, as it decompresses the joint, thus relieving pressure and pain in children who have significant swelling. Therapeutic joint injection involves the administration of glucocorticoids to suppress joint inflammation. In pediatric patients who present for the first time with a swollen joint, aspiration of the synovial fluid is recommended even if the patient does not appear to have a septic joint. Synovial fluid assessment guides diagnosis and management.
Diagnostic indications — In children with arthritis, joint aspiration is most often performed to differentiate bacterial (septic) arthritis from other inflammatory conditions. Arthrocentesis is of limited diagnostic value in children whose joint inflammation is not thought to be infectious in origin. Thus, other causes of arthritis should be investigated if the synovial fluid is not suggestive of an infectious etiology, unless grossly bloody fluid is found.
Certain characteristics of synovial fluid, such as color, clarity, and viscosity, can give the clinician clues about the etiology of the effusion. Laboratory findings are also helpful in differentiating the different types of synovial fluid (see "Synovial fluid analysis"):
●Normal synovial fluid is clear or pale yellow, viscous, and usually has less than 200 white blood cells (WBC)/mm3 with <25 percent polymorphonuclear neutrophils (PMNs).
●In inflammatory arthritis, the fluid is usually yellow and viscous, and the WBC count can range from 2000/mm3 to as high as 75,000/mm3 and typically has a neutrophilic predominance.
●Grossly bloody fluid suggests either a bleeding diathesis or tenosynovial giant cell tumor (TGCT), which was formerly known as pigmented villonodular synovitis (PVNS).
●Synovial fluid from a septic joint is usually opaque (may be green), of variable viscosity, and can have upwards of 300,000 WBC/mm3, at least 75 percent of which are PMNs. Synovial fluid glucose levels decrease in the setting of infection and are usually <50 percent of serum glucose .
However, a lower synovial fluid WBC count does not reliably rule out septic arthritis, and Gram stain is positive in less than 50 percent of samples from infected joints . Thus, empiric antibiotic therapy is administered promptly after aspiration in all patients with signs and symptoms suggestive of septic arthritis and is continued until culture results are available. Severe joint damage can occur if a septic joint is not treated within days . (See "Bacterial arthritis: Clinical features and diagnosis in infants and children" and "Bacterial arthritis: Treatment and outcome in infants and children", section on 'Empiric parenteral therapy'.)
The different subtypes of juvenile idiopathic arthritis (JIA) are not reliably distinguished from each other based upon synovial fluid analysis. They are diagnosed based upon clinical parameters, laboratory profile, and family history. However, children with documented JIA may subsequently develop infection in a concurrently arthritic joint and thereby require joint aspiration to differentiate between the two. Other conditions in the differential diagnosis of noninflammatory arthritis include orthopedic injuries, leukemic synovitis, and neurologic conditions such as Charcot arthropathy. Gout and other crystal-induced inflammatory conditions, in which arthrocentesis is often diagnostic, are rare in children and adolescents. (See "Oligoarticular juvenile idiopathic arthritis", section on 'Differential diagnosis' and "Evaluation of the child with joint pain and/or swelling", section on 'Differential diagnosis'.)
Therapeutic indications — Therapeutic indications include aspiration of painful fluid collections and injection of glucocorticoids [4,5].
Joint aspiration — Joint aspiration may be both diagnostic and therapeutic in patients who have large effusions. The nociceptors that innervate the joint capsule are stimulated by pressure, so decompression of the joint via aspiration helps to relieve this pain . However, fluid is likely to rapidly reaccumulate if appropriate therapy is not given. For patients with septic arthritis, surgical drainage via either open arthrotomy or serial aspirations remain the procedures of choice for fluid removal in children , particularly if the aspirated synovial fluid is purulent [8,9]. (See "Bacterial arthritis: Treatment and outcome in infants and children".)
Joint injections — Intraarticular glucocorticoid injections are often used to treat inflammatory arthritis [4,5,10-12]. They are most commonly used as initial management (in conjunction with nonsteroidal antiinflammatory drugs [NSAIDs]) in children with oligoarticular JIA. However, they are also effective in polyarticular JIA to expeditiously control disease flares while initiating or adjusting systemic medications. Antibiotics are not administered intraarticularly in children with septic arthritis, since intravenous antibiotics reach sufficient concentrations in the synovial fluid. Furthermore, introducing antimicrobials directly into the joint may cause an increased inflammatory response . The use of intraarticular glucocorticoids as adjunctive therapy in children with oligoarticular and polyarticular JIA is discussed in greater detail separately. Specific agents and dosing are discussed below. (See "Oligoarticular juvenile idiopathic arthritis", section on 'Initial therapy' and "Polyarticular juvenile idiopathic arthritis: Treatment", section on 'Intraarticular glucocorticoids' and 'Drugs and dosing for joint injection' below.)
CONTRAINDICATIONS — Contraindications to arthrocentesis or intraarticular injection of a noninfected joint include:
●Infection of the overlying skin or soft tissue
●Allergy to any of the medications being considered for injection
Patients should be screened for bleeding risk by taking a thorough clinical history (family, surgical, dental, obstetric, traumatic injury, medications), with tests of clotting function performed if an increased risk of bleeding is identified . There does not seem to be an increased risk of bleeding complications in patients on anticoagulation who undergo joint aspiration or injection [16,17]. In patients with hemophilia, preprocedural factor VIII (FVIII) is recommended followed by postprocedural rest .
TECHNIQUE — Both arthrocentesis and intraarticular glucocorticoid injections should be performed by experienced practitioners following an explanation of the process as well as the indications, risks, and benefits of the procedure.
Anesthesia — There is no standardized method for delivering anesthesia to children undergoing joint injections . Many children will tolerate arthrocentesis in the office setting with the aid of topical or injected local anesthesia and appropriate reassurance. Procedural anxiolysis, moderate or deep sedation, and general anesthesia are anesthesia options for children who have significant anxiety about procedures, children who are uncooperative, children receiving multiple joint injections, and children with a prior negative experience [20-22]. A minimal anxiolysis/sedation (MAS) protocol is an alternative to general anesthesia in patients undergoing intraarticular glucocorticoid injections into larger joints such as the knee. This protocol uses Child Life services, a topical numbing medication, and nitrous oxide and intranasal fentanyl administered by a sedation service. One study noted a 33 percent reduction in operating expenses when intraarticular injections were performed in this manner versus in the operating room . The various types of anesthesia are reviewed in greater detail separately. Specifics related to joint injection and aspiration are reviewed below. (See "Clinical use of topical anesthetics in children" and "Subcutaneous infiltration of local anesthetics" and "Procedural sedation in children: Approach".)
Lidocaine 1% without epinephrine is the most commonly used local anesthetic given its rapid onset of action. It is used topically or subcutaneously to locally anesthetize the skin at the site of needle entry as well as subcutaneously in the tissue along the anticipated track of the needle. Many clinicians also use "buffered lidocaine," which is lidocaine that is buffered with sodium bicarbonate to reduce the pH of the preparation and thus reduces the burning sensation of the lidocaine . Lidocaine can also be delivered using a needle-free jet injection system (known as a "J-tip"), which is helpful for those children who have significant needle phobia . This delivery system is not painful, but it is loud and can startle patients, so they should be forewarned. Local anesthetics should not be mixed with the glucocorticoid preparation, as these agents (lidocaine, bupivacaine, etc) are chondrotoxic. (See 'Drugs and dosing for joint injection' below.)
Iontophoresis is another method of delivering anesthesia. It uses electric currents rather than carbon dioxide to drive lidocaine into the skin and has a more limited application because it can cause burns, is painful, and has a slower onset of action and shallower penetration than the jet injection system .
Ethyl chloride spray is also commonly used to "freeze" the area of intended needle insertion prior to injection . Eutectic mixture of local anesthetics (EMLA) cream (a combination of topical lidocaine 2.5% and prilocaine 2.5%) can be applied topically 30 to 60 minutes before a procedure to decrease the pain of the needle stick. In a randomized trial of 31 children, EMLA was found to be no more effective than placebo for preventing injection site pain . However, despite this finding, some feel that the placebo effect is helpful .
Needle and syringe size — The needle and syringe used should be appropriate to the size of the joint and degree of effusion :
●A 22-gauge 1.5 inch needle is recommended for arthrocentesis of most joints, such as the knee, ankle, hip, elbow, or shoulder, due to the viscosity of the synovial fluid. A larger-bore needle, either 18 or 20 gauge, is often used to drain large knee effusions or Baker's cysts as the fluid can be quite gelatinous and difficult to aspirate. Longer needles, such as spinal needles (either 2.5 or 3.5 inch), are often necessary to access the deeper joints, such as the hip or shoulder. Smaller joints such as wrists, fingers, and toes are more appropriately accessed with a smaller 25-gauge or 27-gauge needle (1.25 inch or shorter, depending upon the joint).
●Syringe size is dependent upon the amount of fluid the clinician intends to remove. Only a small amount (approximately 5 mL) is necessary for diagnostic purposes. A larger syringe (20 to 50 mL) is useful if a greater amount of fluid is to be removed.
Sterile preparation — Appropriate aseptic technique should be used when performing joint aspiration/injection. The area should be sterilized with either povidone-iodine or chlorhexidine. A sterile drape may be used, and sterile gloves are recommended. If ultrasound guidance is used, a sterile probe cover is also recommended if the needle may come in contact with the gel . (See "Infection control in the outpatient setting", section on 'Safe injection practices' and "Infection prevention: Precautions for preventing transmission of infection", section on 'Standard precautions'.)
Anatomic approaches — The provider performing the procedure should have a thorough knowledge of the anatomy of the joint [30-33] and should choose the shortest path possible to the target while taking care to avoid nerves, blood vessels, and tendons . The preferred anatomic approaches for the following joints are shown in the accompanying figures (figure 1A-G).
Imaging — Ultrasonography is the most commonly used imaging modality to assist with accurate needle placement for aspiration/injection [35,36]. Aspiration/injection of the temporomandibular , hip, shoulder, and ankle joints is often performed with computed tomography (CT) or fluoroscopic guidance, but ultrasound guidance (if available) obviates the need for CT or fluoroscopy and reduces radiation exposure for these patients. Ultrasonography is also helpful when injecting the ankle and wrist joints as there are several joint spaces in each that do not always communicate, often necessitating multiple injections. Tenosynovial effusions are also easily accessed using ultrasound. The ready availability of ultrasonography has made it the technique of choice for these procedures. However, it is important to have a competent ultrasonographer for the procedure. (See "Polyarticular juvenile idiopathic arthritis: Treatment", section on 'Intraarticular glucocorticoids'.)
Synovial fluid collection — Synovial fluid should be collected in a heparinized syringe so that clot formation does not preclude enumeration of leukocytes. Collection and analysis of synovial fluid are discussed in greater detail separately. (See "Synovial fluid analysis".)
Injection — The clinician should always aspirate the joint before injecting glucocorticoids into it to confirm that the needle is in the joint space . There are limited data in children regarding this topic, but, in adults with rheumatoid arthritis, complete aspiration of the synovial fluid prior to the injection of glucocorticoid leads to more sustained remission . Aspirated synovial fluid should be straw colored, not bloody or purulent. If it is either of the latter, glucocorticoids should not be injected until further work-up is done, since the swelling may be due to infection, hemarthrosis, or a tenosynovial giant cell tumor (TGCT). After aspiration, the syringe containing the aspirated fluid should be removed, and the syringe containing the glucocorticoid should be attached. To facilitate the exchange of syringes, a sterile hemostat may be used to hold and stabilize the needle within the joint space while changing syringes. Alternatively, a "reciprocating syringe" enables one to aspirate and inject a joint using the same needle without having to exchange syringes . This approach results in decreased procedure time and less procedural pain. However, these syringes are more expensive than regular syringes, are cumbersome to hold, and are not readily available in most clinics .
Additional precautions — Clinicians performing joint aspiration in a child with a joint effusion and pain should not only evaluate the joint but also the surrounding bones. Children with early osteomyelitis may develop a sterile sympathetic effusion (which appears benign) in the adjacent joint. Sympathetic effusions may also occur in children with leukemia or other neoplastic conditions. Failure to recognize these conditions in a timely fashion may lead to a worse prognosis. (See "Hematogenous osteomyelitis in children: Clinical features and complications", section on 'Clinical features' and "Overview of common presenting signs and symptoms of childhood cancer", section on 'Bone and joint pain'.)
DRUGS AND DOSING FOR JOINT INJECTION — Historically, triamcinolone hexacetonide was the glucocorticoid of choice for intraarticular injections in patients with juvenile idiopathic arthritis (JIA) due to its long duration of action compared with other glucocorticoid preparations, such as the commonly used triamcinolone acetonide [42-46], and milder side effects. Compared with triamcinolone acetonide, triamcinolone hexacetonide is a larger molecule with lower solubility. Thus, it is released more slowly into the joint, presumably contributing to its longer duration of action. Triamcinolone hexacetonide is also released into the systemic circulation more slowly, which is probably the reason that less systemic toxicity is seen with triamcinolone hexacetonide . Specifically, one sees less adrenal suppression with triamcinolone hexacetonide compared with triamcinolone acetonide. Triamcinolone hexacetonide has not been commercially available in the United States for over a decade; however, other medications with the same chemical formulation have been imported from Europe under the US Food and Drug Administration (FDA) Personal Importation Program (PIP). US FDA approval is pending. However, most providers use triamcinolone acetonide, which is readily available. Another alternative is methylprednisolone acetate.
There are no established dosing guidelines for intraarticular glucocorticoid injections in JIA. Doses of these medications often vary according to age and weight of the child, size of the vial, and the provider's experience .
●In general, triamcinolone acetonide is the most commonly used intraarticular glucocorticoid. Historically, 1 mg/kg of triamcinolone acetonide to a maximum of 40 mg was used in large joints (such as knees, shoulders, hips), up to 20 mg in medium-sized joints (such as ankles, wrists and elbows), and between 5 to 10 mg in small joints (fingers, toes). More recent data suggest that increasing the dose of triamcinolone acetonide is associated with better outcomes in terms of duration of remission. In two studies, for example, triamcinolone acetonide dosing up to 2 mg/kg (or 80 mg) for large joints and up to 60 mg for medium joints led to longer-lasting remission [43,44].
●Triamcinolone hexacetonide doses vary according to joint: 1 mg/kg up to 40 mg for knees, 0.75 mg/kg up to 30 mg for ankles and elbows, 0.5 mg/kg up to 20 mg for wrists, and 5 to 10 mg for the small joints of the hands and foot [43,48]. The maximum dosing per joint of triamcinolone hexacetonide is often used regardless of the age or weight of the patient.
●Methylprednisolone acetate is another glucocorticoid preparation that is occasionally used in smaller or more difficult to access joints. It is more concentrated, enabling more medication to be administered into the joint. It is generally used at doses of 5 to 10 mg for small joints and 20 to 40 mg in the subtalar and intertarsal joints [46,48]. It is more soluble, and some data suggest there is less subcutaneous atrophy compared with the other glucocorticoid formulations (triamcinolone acetonide and triamcinolone hexacetonide).
There are also no established guidelines about the number of glucocorticoid joint injections patients with JIA can receive. However, in general, three joint injections per joint per year is considered the limit .
In the past, it was customary to mix local anesthetics (usually lidocaine) with the glucocorticoid preparation to provide temporary pain relief for an intraarticular injection. However, data have since shown the chondrotoxic effect that local anesthetics can have in a joint [50,51]. This chondrotoxic effect was seen with lidocaine even at low doses and was greater when local anesthetics were combined with glucocorticoids. Thus, lidocaine or other anesthetics are not used for intraarticular injection. A small volume of sterile saline may be used to flush the needle before withdrawing it from the joint to help prevent extravasation of the glucocorticoid, which can lead to skin atrophy and dyspigmentation (excluding fingers and toes where the joint space is too small to accommodate any additional fluid).
Biologics such as tumor necrosis factor (TNF) inhibitors have been used selectively as intraarticular therapy in patients with JIA. This practice is not common, however, and has been mainly reserved for temporomandibular joint (TMJ) synovitis who have failed both intraarticular glucocorticoids as well as systemic TNF therapy. There are small studies and case reports that have investigated the response of different joints to varying doses of intraarticular TNF inhibitors (including adalimumab, etanercept, and infliximab) with mixed results . Some studies have shown limited benefit [53,54], whereas other results appear more promising .
POSTINJECTION CARE — In the past, patients were advised to refrain from excessive activity for 24 to 48 hours after intraarticular glucocorticoid injections. However, the data on this recommendation stem from studies on knee arthritis in adults. There is very little pediatric literature on this topic, but what is available suggests that certain joints, such as the wrists and elbows, do not have better outcomes after joint immobilization [56,57]. In addition, there is no evidence to support the common recommendation to not bathe or shower for 24 hours after a glucocorticoid injection.
COMPLICATIONS — Complications due to joint aspiration or injections in children are infrequent and rarely serious .
Postinjection inflammatory reaction — An inflammatory reaction thought to be secondary to irritation of the synovium by microcrystals of glucocorticoids can follow intraarticular glucocorticoid injections . This inflammatory reaction rarely occurs in children [60-62]. Postinjection inflammatory reactions occur soon after the injection and resolve spontaneously within two days and are treated conservatively with local application of ice and appropriate analgesics. Repeat aspiration to exclude iatrogenic infection is necessary if the joint is red, hot, or painful or the patient develops a fever. In general, infection is more likely if joint pain, swelling, and redness last longer than 48 hours or these symptoms begin more than 48 hours postinjection.
Subcutaneous atrophy and depigmentation — Subcutaneous atrophy and depigmentation may occur if there has been leakage of the glucocorticoid into the soft tissues at the time of intraarticular glucocorticoid injection . The reported incidence of this complication varies from 1 to 8 percent of intraarticular glucocorticoid injections [62,64,65]. These changes usually resolve over the course of one to two years.
Intraarticular calcifications — Calcifications are often incidental findings on imaging following intraarticular glucocorticoid injection [66-68] and are usually located periarticularly or in the joint capsule. Almost all patients are asymptomatic [62,66,67]. The pathogenesis of these calcifications is unclear.
Infection — Iatrogenic septic joint after intraarticular glucocorticoid injection is rare. There are little data in children, but, in adult patients who have received joint injections, the rate of iatrogenic infection is between 0.002 and 0.07 percent . Preventive steps to avoid this complication include use of aseptic technique and avoiding injection if there is bacteremia or overlying tissue infection. (See 'Sterile preparation' above and 'Contraindications' above.)
Hemorrhage — As with any invasive procedure, the possibility of bleeding exists. Hemarthrosis following injection is rare. Aspiration of a large amount of blood at the time of the procedure suggests the possibilities of trauma, a bleeding disorder (eg, hemophilia), vascular malformation, or a tenosynovial giant cell tumor (TGCT). Of note, arthrocentesis and joint injections appear to be safe and well tolerated in those receiving anticoagulation . (See "Overview of hemarthrosis".)
There is a low risk of hemorrhage in patients with significant thrombocytopenia. The patient can be given a platelet transfusion if there is an urgent reason for doing the aspiration in the face of a critically low platelet count. In this setting, consultation with a pediatric hematologist is useful.
Effects on growing articular cartilage — The limited available data suggest that there is no long-term negative effect of glucocorticoids upon articular cartilage in childhood.
●In a study of 14 children with chronic arthritis, magnetic resonance imaging was performed before and seven weeks and 13 months after glucocorticoid injection . There was no evidence of cartilage deterioration and no effect upon skeletal growth.
●In a second study, 30 children were followed with plain radiographs after intraarticular glucocorticoid injections for chronic arthritis. No evidence of cartilage damage was found .
SYSTEMIC EFFECTS OF INTRAARTICULAR GLUCOCORTICOIDS — Following the injection of intraarticular glucocorticoids, patients often note improvement in joints that were not injected, consistent with the notion that there is also some systemic absorption of the injected glucocorticoid [10,11]. Studies in both children and adults have noted transient suppression of endogenous cortisol following injection [72,73]. Cushing syndrome has been reported in juvenile idiopathic arthritis (JIA) patients receiving intraarticular glucocorticoid injections with either triamcinolone acetonide or triamcinolone hexacetonide [46,74]. Patients with type 1 diabetes often experience fluctuations in their blood sugar levels for days, necessitating more frequent insulin adjustments. Leukocytosis has been reported, with a neutrophilic predominance after intraarticular glucocorticoid therapy. Facial and body flushing, emotional lability, menstrual irregularity, sleep disturbance, increased appetite, weight gain, and acne are also commonly reported after intraarticular glucocorticoid injections [75,76]. Systemic side effects, particularly adrenal suppression, are more common after intraarticular injection with triamcinolone acetonide or betamethasone compared with triamcinolone hexacetonide  because triamcinolone acetonide has a higher solubility and resultant peak plasma levels than triamcinolone hexacetonide [77,78]. There is a direct relationship between peak plasma glucocorticoid levels and endogenous hydrocortisone suppression . (See 'Joint injections' above.)
SUMMARY AND RECOMMENDATIONS
●Diagnostic and therapeutic indications – Joint aspiration and injections are used for diagnostic and therapeutic purposes in the care of children with arthritis. In pediatric patients, synovial fluid aspiration is used primarily to evaluate for infection, but it can also provide relief in children with large effusions through decompression of the joint space. Intraarticular glucocorticoid injections are used to treat inflammatory arthritis. It is important to rule out infection prior to injecting glucocorticoids into a joint. (See 'Introduction' above and 'Diagnostic indications' above and 'Therapeutic indications' above.)
●Anesthesia – Many children will tolerate arthrocentesis in the office setting with the aid of local anesthesia and appropriate reassurance. However, procedural sedation or general anesthesia should be used in children who are uncooperative, have significant anxiety about the procedure, or are undergoing multiple joint injections. (See 'Anesthesia' above.)
●Selection of needle and syringe size – Needle and syringe size should be chosen based upon both the size of the joint and the size of the effusion. Larger-bore needles are necessary when aspirating fluid due to the viscosity of synovial fluid. Smaller-bore needles are necessary when injecting superficial joints, such as wrists and fingers, to minimize the incidence of skin atrophy and depigmentation that may result from extravasation of glucocorticoid from the joint. (See 'Needle and syringe size' above.)
●Sterile preparation – The implementation of sterile technique during aspiration/injection is essential to prevent iatrogenic infection. (See 'Sterile preparation' above.)
●Anatomic approaches and use of ultrasound guidance – A complete understanding of the joint and surrounding nerves and vessels is important when performing palpation-guided joint aspiration and/or injection. The site of aspiration and/or injection should take into account the shortest and safest route possible, minimizing tissue injury and avoiding nerves and vessels. Ultrasound-guided aspirations and injections are becoming more common and enable providers to visualize their trajectory and avoid important structures. However, they should only be performed by providers competent in the use of musculoskeletal ultrasound. (See 'Anatomic approaches' above and 'Imaging' above.)
●Complications – In children, complications due to joint aspiration or injections are infrequent and rarely serious. Patient education before and after the procedure should include discussion of the risks, including infection, skin depigmentation, soft tissue atrophy, crystal reactions, as well as more common side effects of intraarticular glucocorticoids, such as flushing, menstrual irregularities, and emotional lability. (See 'Complications' above and 'Systemic effects of intraarticular glucocorticoids' above.)
ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Thomas JA Lehman, MD, who contributed to earlier versions of this topic review.
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