<3mo: ultrasound<unk> 
>3mo: AP pelvis with both legs extended in neutral abduction
Shenton's line on XR (imaginary line continuous along inferior border of superior pubic ramus and medial neck of femur)
Acetabular angle should be <30'
Developmental dysplasia of hip
Acute rheumatic fever
Avascular necrosis of hip
Ankle dislocation
Femur fracture
Hip bursitis
Juvenile idiopathic arthritis
Elbow dislocation