Positioning is extremely vital to help prevent contractures that can cause problems when fitting a prosthesis.
If you are going to be sitting in a wheelchair you should always have your knee straight (extended) as opposed to hanging down (flexed).
If you sit with your knee bent (flexed) for a long period of time, the limb may develop a contracture and prolong the necessary therapy. This will negatively effect your rehabilitation. Contractures can cause you to be uncomfortable in your prosthesis and/or effect how well you are able to walk. If a severe enough contracture occurs, this will limit your prosthetic options and candidacy.
Proper positioning can be achieved with the use of an extension board that will be provided by the physical therapist or prosthetist.
When lying in bed remember to keep your knee as straight as you can. Never prop a pillow under the knee because this can also cause unwanted contractures.