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

Frequency:

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

Mortality/Morbidity:

• Controversy exists regarding a possible etiologic relationship between TS and Legg-Calvé-Perthes disease (LCP). Although some children with TS 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 TS develop LCP. Coxa magna, osteoarthritis, or recurrences may occur.

Sex:

• TS affects boys twice as often as girls.

Age:

• TS most frequently occurs when individuals are aged 3-10 years; however, TS has been reported in a 3-month-old infant and in adults. Nonetheless, regard children outside the typical age group with suspicion. Some teenagers with enthesitis-associated arthritis initially are diagnosed erroneously with toxic synovitis when they first present with hip pain.

History:

• Hip pain: Unilateral hip or groin pain is the most common complaint; however, some patients with TS may complain of medial thigh or knee pain.

• Crying at night: Very young children with TS may have no symptoms other than crying at night; however, a careful examination should reveal some degree of an antalgic limp.

• Recent infection: Recent history of an upper respiratory infection, pharyngitis, bronchitis, or otitis media is elicited from approximately one half of patients with TS.

• Limp: Some patients with TS may not complain of pain and may present with only a limp.

• Fever: Children with TS usually are afebrile or have a mildly elevated temperature; high fever is rare.

Physical:

• Hip

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

• Examination of the individual with TS usually reveals mild restriction of motion, especially to abduction and internal rotation, although one third of patients with TS 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 TS 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.

• Knee

• The knee of the individual with TS 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.

Causes:

• No definitive cause of TS is known, although the following have been suggested:

• Patients with TS 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 TS.

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

Lab Studies:

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

• Erythrocyte sedimentation rate: The erythrocyte sedimentation rate (ESR) may be elevated slightly. 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.

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

Imaging Studies:

• Anteroposterior and lateral radiographs of the pelvis

• 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.

Medical Care:

• Apply heat and massage to individuals with TS.

• If diagnosis of TS is equivocal or the patient is uncomfortable, hospitalize for observation and traction. Home treatment can include traction. Skin traction of the hip in 45° of flexion minimizes intracapsular pressure.

Activity:

• Advise bedrest for 7-10 days, allowing the patient to rest in a position of comfort.

• Advise the patient with TS not to bear weight on the affected limb.

• Advise the patient with TS to avoid full unrestricted activity until the limp and pain have resolved.

Further Outpatient Care:

• Advise patients with 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 TS have repeat radiographs within 6 months to exclude LCP disease.

In/Out Patient Meds:

• Advise NSAIDs (eg, ibuprofen, naproxen).

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 TS.

• LCP disease develops in 1-3% of individuals with TS.

Prognosis:

• Patients with TS usually experience marked improvement within 24-48 hours.

• Two thirds to three fourths of patients with TS have complete resolution within 2 weeks. The remainder may have less severe symptoms for several weeks.

• Recurrence rate is 4-17%; most recur within 6 months.

• No increased risk of juvenile chronic arthritis is known; however, a slightly increased risk for later development of osteoarthritis may exist.

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.