Differentials
Septic arthritis
SIGNS / SYMPTOMS
Acute onset.
Systemic symptoms.
Unilateral involvement.
Acute pain in the hip.
Marked restriction in movement.
INVESTIGATIONS
Elevated WBC count.
Positive blood cultures.
X-ray shows widened joint space.
Joint effusion on ultrasound examination.
Joint aspiration may confirm the infection.
Transient synovitis of the hip
SIGNS / SYMPTOMS
Acute onset.
Prior history of viral illness.
Mild systemic features.
Unilateral involvement.
Restricted motion with minimal pain.
Spontaneous improvement over 24 to 48 hours.
INVESTIGATIONS
Normal WBC count.
Negative blood cultures.
Normal radiographs.
Ultrasound examination shows joint effusion.
Joint aspiration is sterile.
Sickle cell disease
SIGNS / SYMPTOMS
Acute abdominal pain.
Systemic symptoms.
Unilateral involvement with associated long bone osteomyelitis.
INVESTIGATIONS
Sickling test positive.
Juvenile idiopathic arthritis
SIGNS / SYMPTOMS
Acute or chronic presentation.
Single or multiple joint involvement.
Systemic symptoms.
Effusion of the affected joints.
Recurrence of acute episodes.
INVESTIGATIONS
High WBC count in acute phase.
Rheumatoid factor (polyarticular JIA) or antinuclear antibodies (oligoarticular JIA) positive.
Joint aspirate shows white cells, no crystals or organisms.
Radiographs may show decreased joint space.
Multiple epiphyseal dysplasia (Meyer disease)
SIGNS / SYMPTOMS
A rare genetic disorder resulting in bilateral epiphyseal dysplasia with both hips at the same stage and with the same degree of involvement. Although Legg-Calvé-Perthes disease can be bilateral, it is more likely to be sequential than simultaneous.
INVESTIGATIONS
Sequential films show continued disease equality and other joint epiphyseal involvement.
Spondyloepiphyseal dysplasia
SIGNS / SYMPTOMS
Bilateral Perthes disease with spine involvement, known as platyspondyly.
INVESTIGATIONS
Spine radiographs demonstrate features of platyspondyly, which are a flattened vertebral body shape with reduced distance between end plates.
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