1 & half year old dog, 45 pounds, after FHO surgery for hip displacement 2 months ago slips/falls on floor?

My dog (female, approx 1 year and 7 months old, 46 pounds (21 kg) was playing with another dog rather wildly and fell off a low ledge. We took her to the vet because she was whimpering and favoring her right hind leg, and it turned out to be hip displacement. She had FHO surgery to correct it a little more than 2 months ago. She has since started walking, running, and playing again, although she refuses to jump up the stairs and on the furniture like she used to. Now, however, her hind legs start shaking for no clear reason and she has been slipping and falling almost everytime she tries to walk on our hardwood floor in the kitchen. She never had a problem with slipping before, yet now she is terrified of the floor and is violently falling down, legs splayed out and flat on her belly, every time she tries to walk through the kitchen. This worries me greatly, and I'm wondering if I should lay down mats or install a carpet or do something, anything, and if this is a normal rate of recovery and improvement in dogs who've had FHO surgery after two months? Any insight at all would be greatly appreciated.