My daughter was born 30 years ago, with "clicky hips". I was utterly distraught, but once I'd calmed down, and had the cause and treatment explained to me, it was no problem.
It is a condition more common in girls than boys.
My daughter had both legs put in plaster from ankle to hip, with the legs placed in the "frog" position, with a pole between the ankles to keep the legs in that position. That was a boon for nappy changing - I had a handle to grab rather than grappling with two wriggling legs
She was in plaster for six weeks, and then changed to what I think was called a Pavlik harness, which had a series of straps and buckles that kept the legs in the same frog position, but could be lengthened to allow some kick room.
She was in that for a further six weeks, and by that point the hip's ball and socket joint had developed enough that she was signed off.
She never had any problems with her hips after that, and went on to do trampolining, swimming and horse riding without any problems.
Apparently another treatment back in the olden days, were to use double thickness towelling nappies.
I'm pleased to see above that your granddaughter has been given a clean bill of health with her hips, but for anyone else who has a child diagnosed with this CDH (congenital dislocation of the hips) it is 99% of the time a very easy fix .