We've had people come back from long-term sick leave on staged returns. Reasons have included depression, cancer treatment, bad accident that resulted in a long time in hospital.
Some have started back on a couple of hours a day, others in two or three full days a week when they normally work full time. It depends in how long they have been of sick, what their doctor has recommended, and why they have been off - different conditions may need different treatment, whether it's a question of rebuilding physical or mental stamina, and also the role itself, whether it's desk-based or physically active and so on.
So there are lots of different factors that will make a difference to what is suitable or not.
I broke my foot at work and I had a stand up all day role. When it was healed I went back just 4hrs a day instead of 8hrs just because it was still quite sore. I was allowed to sit down whenever I wanted as well and they were very supportive, I went up to 6hrs and finally back to 8 over a period of about 6 weeks.