I found this excellent article on the Independent Living NSW website
Question: I am having trouble getting up and down the stairs in my house due to mobility difficulties and pain in my knees. I think I need a stairlift, what do I do?
Answer: Staircases are all very different – the first stage I would advise anyone is to have is an assessment with an Occupational Therapist and they will be able to advise you re funding and the types of stairlifts that are appropriate for your situation.
There are straight and curved staircases for internal and external flights of stairs/steps. There are lifts that are specially designed to go externally and are specifically durable for outdoor conditions. It may also be a fact that the stairs cannot accommodate a stairlift so in this case a through floor lift would need to be considered.
For internal stairs if it is a straight flight then depending on staircase width and access at the top and bottom of stairs a track runs along the side of the stairs with either a chair or a standing platform. I would suggest if you are having difficulties climbing the stairs then you would perhaps need a chair version stairlift.
If your stairs has a curve or mid way platform, then the stairlift you will need will have to be custom made to the shape and layout of the stairs. In any case you will need to get suppliers out to assess the situation.
There are many different suppliers of stairlift so it is worth shopping around as there are differences in make and models.