7 week old needs ultrasound

Sarah

I brought my daughter to her regular check up at 5 weeks. The doctor said he noticed a clicking noise in her hip so he would like an ultrasound done. Does anyone know how they go about doing an ultrasound on a baby this little? And why they want one for a clicking noise? Her appointment is tomorrow morning, I’m a little nervous just cause I’m sure it’s going to make her upset 😢