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Transient synovitis - ankle

Case contributed by Michael Yang
Diagnosis certain

Presentation

Presents with acute left ankle pain and associated swelling started at school. No history of trauma. No past medical history.

Patient Data

Age: 5 years old
Gender: Male
x-ray

Moderate diffuse fullness and swelling of the "ankle joint" is consistent with an ankle joint effusion.

Mild cortical irregularity of the medial malleolus. No definite acute displaced fracture or dislocation.

Subcentimeter sized irregular density in the ball of the heel with adjoining lucency may represent a foreign body/gravel in a superficial ulceration. 

The bone density is normal.

x-ray

No acute displaced fracture or dislocation considering limited technique.

No ankle joint effusion.

No abnormal calcifications. 

Case Discussion

5 year old boy presents with acute left ankle pain and associated joint swelling with no history of trauma. ESR and WBC were within normal limits. The patient was placed in a posterior short leg splint and advised to be non-weight bearing. Improved over the course of 2 weeks.

Transient synovitis (TS) is a benign and self-limiting condition that involves inflammation that typically occurs in the hip joint. Although the exact cause of TS remains under investigation, it is commonly associated with a viral infection in children between 3 and 8 years old.

TS of the hip in children presents with pain, refusal to bear weight, fever, and limp. A fraction of children presenting with a limp also has ankle and knee joint involvement. TS usually resolves within 3-10 days with RICE treatment, and resolution of joint effusion occurs after 1 week.

It is crucial to differentiate TS from septic arthritis. Fever (temperature >38.0 C) and elevated CRP (>20 mg/L) are the most significant predictors for septic arthritis. Imaging can be very helpful, and plain radiographs typically range from normal to joint space widening.  MRI can be used to distinguish the two conditions in complicated cases. The characteristics findings of TS on MRI include joint effusions and absence of signal intensity abnormalities in the bone marrow.

Though the other differential considerations for ankle joint effusions include early-onset Juvenile Rheumatoid Arthritis (JRA), Juvenile Idiopathic Arthritis (JIA), traumatic hemarthrosis, and much less likely leukemia or metastatic disease. An easy mnemonic for causes of the pediatric joint effusion is "TIM" (Trauma, Infection/Inflammation, Malignancy/Miscellaneous).

This case was submitted with supervision and input from:

Soni C. Chawla, M.D.
Associate Professor
Department of Radiological Sciences
David Geffen School of Medicine at UCLA
Olive View - UCLA Medical Center  

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