Spontaneous, symptoms came on over about a 48 hour period from discomfort trying to lie on it in bed, to pain during the next day, very bad pain the following night and restricted mobility had definitely kicked in the morning.
GP pretty much straight away and had diagnosis, only strong painkillers take the edge off it. They do say most resolve themselves over a long number of months but aside from the mobility, painkillers strong enough to work made her too spaced out.
Edit: the dislocation fall was about 20 months post-op, so we expect not a factor at all, she’s had no other previous after effects.