Transient Synovitis 

Updated: Dec 20, 2018
Author: Christine C Whitelaw, MD; Chief Editor: Lawrence K Jung, MD 

Overview

Background

Transient synovitis (TS) is the most common cause of acute hip pain in children aged 3-10 years.[1] The disease causes arthralgia and arthritis secondary to a transient inflammation of the synovium of the hip.

Pathophysiology

Biopsy reveals only nonspecific inflammation and hypertrophy of the synovial membrane. Ultrasonography demonstrates an effusion that causes bulging of the anterior joint capsule. Synovial fluid has increased proteoglycans.

Epidemiology

Frequency

United States

Little data are available regarding the frequency of this illness. However, excluding infections and trauma, transient synovitis is one of the most common causes of joint pain in the pediatric age group.

International

The Netherlands report an incidence of 76.2 per 100,000 person-years.

Mortality/Morbidity

The possible etiologic relationship between transient synovitis and Legg-Calvé-Perthes disease (LCP) is controversial.[2] Although some children with transient synovitis may develop LCP, whether persistence of increased intraarticular pressure eventually causes avascular necrosis or whether patients may have a synovitis that occurs before detection of femoral head collapse is not fully known. Approximately 1.5% of patients with transient synovitis develop LCP, Coxa magna, osteoarthritis, or recurrences.

Sex

Transient synovitis affects boys twice as often as girls.

Age

Transient synovitis most frequently occurs in children aged 4-10 years;[3] however, transient synovitis has been reported in a 3-month-old infant and in adults. Nonetheless, children outside the typical age group are unlikely to have transient synovitis. Some teenagers with enthesitis-associated arthritis are initially diagnosed erroneously with toxic synovitis when they first present with hip pain.

 

Presentation

History

Unilateral hip or groin pain is the most common symptom reported; however, some patients with transient synovitis (TS) may report medial thigh or knee pain. Transient synovitis has the highest incidence rate among causes of nontraumatic hip pain in children.[4] Guidelines for chronic hip pain have been established.[5]

Very young children with transient synovitis may have no symptoms other than crying at night; however, a careful examination should reveal some degree of an antalgic limp. Recent history of an upper respiratory tract infection, pharyngitis, bronchitis, or otitis media is elicited from approximately half of patients with transient synovitis. A prospective study from the University of Edinburgh Medical School reported that the symptoms of vomiting, diarrhea, or common cold/runny nose were more likely to precede transient synovitis. Other symptoms suggestive of either viral or bacterial infections were not significantly prominent.[6]

Children with transient synovitis are usually afebrile or have a mildly elevated temperature; high fever is rare.

Some patients with transient synovitis may not report pain and may present with only a limp. Guidelines for diagnosis and treatment in children with a limp have been established.[7]

A thorough history should include a description of the pain (location, character, onset, duration, change with activity or rest, aggravating and alleviating factors, night pain); recent trauma; mechanical symptoms (catching, clicking, snapping, worse during or after activity); systemic symptoms (fever, irritability, eating or drinking less); inflammatory symptoms (morning stiffness); neurological symptoms (weakness, altered sensation); weight-bearing status (inability to bear weight or inability to move the leg in children of non–weight-bearing age); effects of any previous treatments (antibiotics, analgesics, anti-inflammatories, physiotherapy); and the current level of function of the child.[8]

Physical

Examination of the hip includes the following:

  • During physical examination, hold the hip in flexion with slight abduction and external rotation.

  • Examination of the individual with transient synovitis usually reveals mild restriction of motion, especially to abduction and internal rotation, although one third of patients with transient synovitis demonstrate no limitation of motion.

  • The hip may be painful even with passive movement.

  • The hip may be tender to palpation.

  • The most sensitive test for transient synovitis is the log roll, in which the patient lies supine and the examiner gently rolls the involved limb from side to side. This may detect involuntary muscle guarding of one side when compared to the other side.

Examination of the knee includes the following:

  • The knee of the individual with transient synovitis may have decreased range of motion only as it may include hip motion.

  • Any effusion or joint abnormality within the knee should suggest another disease process.

The lumbar spine, sacroiliac joint, knee, and abdomen should also be examined. A complete musculoskeletal examination to look for joint swelling should be performed if there is a history of inflammatory symptoms.[8]

Causes

No definitive cause of transient synovitis is known, although the following have been suggested:

  • Patients with transient synovitis often have histories of trauma, which may be a cause or predisposing factor.

  • One study found an increase in viral antibody titers in 67 of 80 patients with transient synovitis.

  • Postvaccine or drug-mediated reactions and an allergic disposition have been cited as possible causes.

 

DDx

 

Workup

Laboratory Studies

The following studies may be indicated in transient synovitis (TS):

  • CBC count: The white blood cell (WBC) count may be slightly elevated.

  • Erythrocyte sedimentation rate (ESR)

    • The erythrocyte sedimentation rate (ESR) may be slightly elevated. One study found that the combination of an ESR greater than 20 mm/h and/or a temperature greater than 37.5°C identified 97% of individuals with septic hip.[9]

    • Another study by Kocher et al used 4 independent predictors of septic arthritis to distinguish it from transient synovitis and the need for further workup.[10] They concluded that patients who were nonweightbearing and had a history of fever, an ESR greater than 40 mm/hr, and a WBC count greater than 12,000 cells/mm had a 99.6% predicted probability of septic arthritis. A 2014 retrospective multicenter study to assess the Kocher predictive algorithm found that because of the overlapping features of K kingae arthritis of the hip and transient synovitis in children younger than 3 years of age, Kocher predictive algorithm is not sensitive enough for differentiating between these 2 conditions. To exclude K kingae arthritis, blood cultures and nucleic acid amplification assay should be performed in young children presenting with irritation of the hip, even in the absence of fever, leukocytosis, or a high Kocher score.[11]

  • Luhmann et al applied these 4 criteria to their patient population and discovered a 59% predicted probability.[12] However, when they applied the 3 criteria of history of fever, a serum WBC count of greater than 12,000 cells/mm, and a previous health-care visit, they found a predicted probability of 71% that the patient had septic arthritis.

  • C-reactive protein

    • C-reactive protein (CRP) level rises within 6 hours after the onset of septic arthritis of the hip and peaks at 2 days.[13]

    • A CRP >2 mg/dL (>20 mg/L) has been found to be an independent risk factor strongly associated with septic hip arthritis.[14]

    • Adding in the CRP as a predictive factor, Jung et al found that patients with 4 of 5 predictors (body temperature >37ºC, ESR >20 mm/h, CRP >1 mg/dL, WBC >11,000/mL, and an increased hip joint space of >2 mm) had a high probability of having septic arthritis and were candidates for further study by MRI or joint aspiration.[15]

    • Singhal et al propose that a CRP value greater than 20 mg/L is the strongest independent risk factor for septic arthritis and that its inclusion within a predictive model eliminates the significance of other variables. They assert that the CRP and WBC count may be measuring a similar process so the relative strength of the CRP minimizes the importance of the WBC count. Their review of 311 records showed that only 2 factors (weight-bearing status and CRP >20 mg/L) were independent in differentiating septic arthritis from transient synovitis. Individuals with neither predictor had a less than 1% probability of having septic arthritis, but those with both had a 74% probability of having septic arthritis.[16]

  • Urinalysis and culture: Both of these tests should be normal.

  • Urine glycosaminoglycans: One study found a decreased level of urine glycosaminoglycans in patients who were diagnosed with Perthe disease, compared with those with transient synovitis and a control group.

  • Procalcitonin levels: These may be helpful in distinguishing between bacterial infections and inflammatory processes. Procalcitonin levels remain low during bouts of inflammatory disease but increase in septic arthritis and may be even more useful in distinguishing septic arthritis from osteomyelitis.[17]

Depending on the history, consider Lyme serology, antinuclear antibody, rheumatoid factor, HLA-B27, and tuberculosis skin testing.[8, 18]

A study’s results suggest that most investigations performed during the initial work-up in patients suspected of transient synovitis of the hip are unnecessary and should routinely include only white blood cell count, C-reactive protein, erythrocyte sedimentation rate, and hip radiography and ultrasonography.[19]

Imaging Studies

Radiographs exclude bony lesions (eg, occult fracture, osteoid osteoma) unless the child had onset of symptoms within 3 days, has no fever, appears well, and has only mildly restricted abduction without guarding against movement in other planes. Plain films may be normal for months after onset of symptoms. Medial joint space may be slightly wider in the affected hip (see the image below).

Widening of the joint space. Note that the space i Widening of the joint space. Note that the space is wider on the left side. Discrepancies greater than 1 mm indicate the presence of fluid.

If excess fluid is present or the patient has early Legg-Calvé-Perthes (LCP) disease, plain radiography may reveal an increase in the teardrop distance (ie, distance between the medial acetabulum and ossified part of the femoral head). Compared with the other side, this distance should be the same or within 1 mm. One half to two thirds of patients with transient synovitis may have an accentuated pericapsular shadow.

In one study, as many as 58% of patients with transient synovitis had the Waldenström sign (ie, lateral displacement of the femoral epiphyses with surface flattening). Other studies have reported a positive obturator sign in established incidents of transient synovitis. This is a prominent shadow caused by the soft tissues that overlie the interpelvic aspect of the acetabulum. Radiography may reveal diminution of the definition of soft tissue planes around the hip joint or slight demineralization of the bone of the proximal femur, particularly in the metaphyseal region.

Although extremely accurate for detecting an intracapsular effusion, ultrasonography does not assist in determining the cause and is used best to guide hip aspiration. An effusion is present if ultrasound demonstrates capsular distension greater than 2 mm. Occasionally, the radiologist can differentiate between transient synovitis and early LCP on the basis of effusion rather than synovial membrane thickening. However, ultrasonography cannot rule out osteomyelitis or soft tissue infection.

In settings in which routine aspirations of effusions is not performed, an MRI may help physicians differentiate transient synovitis from septic arthritis.[20] A study by Lee et al found that septic arthritis demonstrated signal intensity alterations in the bone marrow of the affected hip. Yang et al confirmed this finding in a study on 49 patients with transient synovitis and 18 patients with septic arthritis.[21] He demonstrated not only the statistically significant finding of signal intensity in the bone marrow, but also found signal intensity alterations and contrast enhancement of the soft tissue in patients with septic arthritis. Furthermore, the statistically significant findings in the patients with transient synovitis included contralateral (asymptomatic) joint effusions and the absence of signal intensities in the bone marrow. Both diseases showed ipsilateral effusions with synovial thickening and enhancement.

Dynamic contrast-enhanced MRI findings can be used to differentiate septic arthritis from transient synovitis in the joint.[22]

Other Tests

Bone scintigraphy demonstrates mildly elevated uptake; however, bone scintigraphy may also reveal a transient decrease in uptake of technetium 99m phosphate. Bone scintigraphy does not help the physician differentiate etiologies.

Procedures

Perform aspiration with ultrasonographic guidance in all individuals in whom ultrasonography has exhibited evidence of an effusion and any of the following predictive criteria are present:

  • Temperature greater than 99.5°F

  • ESR greater than or equal to 20 mm/h

  • Severe hip pain and spasm with movement

The aspirate should assist the physician in differentiating transient synovitis from septic arthritis. The physician can confirm 30-50% of septic arthritis incidents with Gram stain. In individuals with septic arthritis, the WBC count varies (25,000-250,000/mcL); however, in these individuals, the WBC count consistently demonstrates 90% polymorphonuclear cells. Also, in persons with septic arthritis, the glucose is often less than 40 mg/dL or is markedly different from the serum glucose.

In one study, 36 children with an effusion underwent aspiration with ultrasonographic guidance. The Gram stain identified 1 child with an acute infection. The 35 children with a negative Gram stain were sent home with no further complications.

In another study published by Skinner et al, 25 children with a clinical diagnosis of transient synovitis were observed.[23] They all had a joint effusion by ultrasound, but no aspiration was performed. The mean age of the patient population was 6 years, the average size of the effusions was 9 mm, and the distribution between the sides affected was equal. They found that by 2 weeks postdiagnosis, all patients were pain and limp free. The effusions, although still present in some, were decreasing in size. They concluded that transient synovitis is benign and can be treated with supportive therapy.

 

Treatment

Medical Care

Apply heat and massage to individuals with transient synovitis (TS). If the diagnosis of transient synovitis is equivocal or the patient is uncomfortable, hospitalize for observation and traction. Home treatment also can include traction. Skin traction of the hip in 45° of flexion minimizes intracapsular pressure. Treatment with ibuprofen may shorten the duration of symptoms.[24]

Activity

Advise bedrest for 7-10 days, allowing the patient to rest in a position of comfort. Advise the patient with transient synovitis not to bear weight on the affected limb. Advise the patient with transient synovitis to avoid full unrestricted activity until the limp and pain have resolved.

 

Medication

Nonsteroidal anti-inflammatory drugs (NSAIDs)

Class Summary

These agents have analgesic, antiinflammatory, and antipyretic activities. They act by inhibiting cyclooxygenase activity, which results in decreased prostaglandin synthesis. Other mechanisms, such as inhibition of leukotriene synthesis, lysosomal enzyme release, lipoxygenase activity, neutrophil aggregation, and various cell-membrane functions, may also exist.

Naproxen and ibuprofen are the most frequently prescribed NSAIDs in children, with a suspension form and safety and efficacy studies available. The COX-2 inhibitors have not yet been studied adequately in the pediatric population.

Naproxen (Aleve, Naprosyn, Anaprox)

NSAID that inhibits cyclooxygenase, thus inhibiting formation of prostaglandins.

Ibuprofen (Motrin, Advil)

NSAID that inhibits cyclooxygenase, thus inhibiting formation of prostaglandins.

 

Follow-up

Further Outpatient Care

Advise patients with transient synovitis (TS) to return in 12-24 hours for a repeat examination. If significant symptoms persist for 7-10 days after the initial presentation, consider other diagnoses. Advise that all patients with transient synovitis have repeat radiography within 6 months to exclude Legg-Calvé-Perthes (LCP) disease.

  • A retrospective study that included 198 children with the diagnosis of a transient synovitis found that between the diagnosis of transient synovitis and a 3-month follow-up, 20 children did not remain symptom-free (10.1%).  4 (2%) of these patients were diagnosed with Perthes disease and the other 16 had a normal radiological follow-up. All children who were symptom-free had negative follow-up X-rays.[25]

Inpatient & Outpatient Medications

Recommend nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and naproxen. NSAIDs may shorten the duration of symptoms. A study performed on 36 children with transient synovitis showed that those who took ibuprofen had a median duration of symptoms for 2 days. The control group taking a placebo had a mean duration of symptoms for 4.5 days.

Complications

Sequelae include coxa magna and mild degenerative changes of the femoral neck. Coxa magna is observed radiographically as an overgrowth of the femoral head and broadening of the femoral neck. Coxa magna leads to dysplasia of the acetabular roof and subluxation. An incidence rate of coxa magna of 32.1% has been reported in the first year following transient synovitis.

LCP disease develops in 1-3% of individuals with transient synovitis.

Prognosis

Patients with transient synovitis usually experience marked improvement within 24-48 hours. Two thirds to three fourths of patients with transient synovitis have complete resolution within 2 weeks. The remainder may have less severe symptoms for several weeks. The recurrence rate is 4-17%; most recurrences develop within 6 months. No increased risk of juvenile chronic arthritis is known; however, a slightly increased risk for later development of osteoarthritis may be noted.

Patient Education

Advise parents and/or caregivers to initially check the temperature of the patient with TS regularly and inform the physician of any fever. For patient education resources, see the Foot, Ankle, Knee, and Hip Center and Arthritis Center.

 

Questions & Answers

Overview

What is transient synovitis (TS)?

What is the pathophysiology of transient synovitis (TS)?

How common is transient synovitis (TS) in the US?

What is the international incidence of transient synovitis (TS)?

What is the morbidity of transient synovitis (TS)?

Is transient synovitis (TS) more common in males or females?

What age group is most commonly affected by transient synovitis (TS)?

Presentation

What is the clinical history of transient synovitis (TS)?

What are physical findings of the hip exam in transient synovitis (TS)?

What are physical findings of the knee exam in transient synovitis (TS)?

What causes of transient synovitis (TS)?

DDX

What are the differential diagnoses for Transient Synovitis?

Workup

Which lab studies are indicated in the workup of transient synovitis (TS)?

What is the role of imaging studies in the workup of transient synovitis (TS)?

What is the role of bone scintigraphy in the workup of transient synovitis (TS)?

When is ultrasonography-guided aspiration indicated in the workup of transient synovitis (TS)?

What is the role of ultrasonography-guided aspiration in the workup of transient synovitis (TS)?

Treatment

What is the medical care for transient synovitis (TS)?

What activity restrictions are indicated in the treatment of transient synovitis (TS)?

Follow-up

What is the follow-up care for patients with transient synovitis (TS)?

Which medications are used in the treatment of transient synovitis (TS)?

What are the complications of transient synovitis (TS)?

What is the prognosis of transient synovitis (TS)?

What is the patient education for transient synovitis (TS)?

Medications

Which medications in the drug class Nonsteroidal anti-inflammatory drugs (NSAIDs) are used in the treatment of Transient Synovitis?